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VIEWS: 29 PAGES: 14

  • pg 1
									SPELEONICS                    # 16    Volume   IV number   4




may, 1991
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                                                                                                     SPELBIIICS 16

                                                                                    Volume IV, Number 4               May, 1991


        SPELEONICS is published approximately four times per
    year by the Communication and Electronics             Section of the                                             Foreign      subscriptions      can be paid       in U.S.      "paper"
    National    Speleological       Society (NSS).     Primary interests                                        dollars      in the mail;        an international        money-order     may
    include cave radio,       underground    communication     and instru.                                      cost     as IIIJch as the subscripti         on i tsel f. Many members
   mentation,    cave-rescue      communications,     cave lighting,     and                                    have sent cash without problems.                 (No foreign     currency,
   cave-related    applications       of amateur radio.      NSS member-                                        please.)
   ship is encouraged       but not required.                                                                       Editorship      rotates     among the officers.       Volunteers    are
        Section   membership,        which   includes   four    issues     of                                   encouraged to guest-edit or produce an issue. A technical
   SPELEONICS, is $4.00 in USA/Canada/Mexico,                $6 overseas.                                       session,      followed by election        of officers,       is an annual
   Send subscriptions          to section   treasurer    Joe Giddens      at                                    event held during the NSS Convention.
   the address below (make checks payable to SPELEONICS.)If                                                         Complimentary copies of SPELEONICS go to NSS offices
   you have a ham-radio callsign or NSS membership                                               number,        and sections,  the U.S. Bureau of Mines, U.S. Geological
   please include them when slbscribing.                                                                        Survey, and the Longwave Club of America.

  Chairman (and editor                         of                  Secretary    (and editor           of
  the next issue):                                                                                              Treasurer    (and editor     of                    Publisher:
                                                                    issue #18)                                  this issue):
   I an    D   rUIIIIOI"Id
                                                                   Frank Reid W9MICV                            Joe Giddens      N5IOZ
  627 Varsity Est.                     Cres.        N.W.           P.O. Box 5283                                                                                   Diana   E. George N9DEJ
  Calgary,   Alberta                                                                                            PO Box 891                                         1869 Trevilian    Way
                                                                   Bloomington,     Indiana                     Camden, Arkansas
  CANADA T3B 3C4                                                   47407-5283                                                                                      Louisville,    Kentucky
                                                                                                                71701                                              40205

  -=-=-=-=-=-=-=-=-=-:-=-                           CONTENTS       -=.=.=-=-:-=-=-:-=.=.=-
                                                                                                                -=-=-:-=-=-:-=-=-=-=-       ANNOUNCEMENTS-=-=-=-:.:-=.:-=-=-

  NEWS      AND              ANNOUNCEMENTS
          Dues increase                                                                                                                                                       ~---_..__..-.-.
          Erratllll                                                                          1                                IMPtRTANT NOTICE:             !XES   IIiCREASE
  1991 NSS CONVENTION ELECTRONICS ABSTRACTS                                              2                                                  .............          ........
 WHEAT(tm)                    LAMP NOTES
                                                                                                                   Postage is our largest           expense.        Thanks mostly         to
                                                                                         2                         our plblisher,     Diana George, we have              held subscrip'
 THE      STANLEY               ESTIMATOR      AND OTHER MISCELLANEOUS                                      I      tion costs constant since our first issue in 1985,
 RAMBLINGS                                                                                                        meanwhile surviving one postal, rate increase.    The
        Jim McConkey                                                                                        I     new increase in January forces us to raise dues to
                                                                                         3                        S1.50per issue (US/Canada/Mexico)and 12.00 over-
 MEASURING                         A
          GROUND CONDUCTIVITY WITH" CAVERADIO                                                               I     seas, effective August 1, 1991. Old and new members
   Brian Pease  W11R                                                                                              may subscribe for any number of future     issues at
                                                                                         4                  I     the old rate until then.
 ROCKijELL GPS RECEIVER                        (reprint)                                                   I
                                                                                         6                 +.....---.-.-----.--.-.----.-.--..-.--.--.--.--.-..---...
 CAVERS          GET HANDS'ON EXPERIENCEWITH GPS NAVIGATION
       Frank Reid                                                                                          ERRAT1II
                                                                                         7                                                                                          0""0
                                                                                                                                                                                      \00/
                                                                                                           Sceleonics 12, p.9, column 2, paragraph 3,
 RESOURCES,
    GPS information
                              REFERENCES,      NEW    PRODUCTS
                                                                                                           line 1 should read:          "...
                                                                                                                                    Detecting Lesser                               =:=\/===

    Whistler Hunter's Guide                                                                                WaxMoths Acoustically."
    Battery Charger References
    Nite lite Co.
    Water'quality   instruments (Cole-Palmer)
    Underwater communications reference                                              8
EARLY      ADVANCES                IN UNDERGROUND          RADIO    COMMUNICATION
    Angelo I. G~rge
                                                                                     9
REJUVENATING SEALED LEAD-ACID                              CELLS
   John De Armond, WD40QC
                                                                                    12
EARTH-DIPOLE                   COMMUNICATION         NOTES
   Pete          Lucas,           Frank Reid
                                                                                    12
PHONE PATCH FOR HANDHELD RADIOS
   Frank Reid                                                                       13


                                                                                                                          Bat gargoyle at Indiana University
                                                                                                                                                           spel.eonics    16
                                                                                                                                              v.   IV   no. 4     May  1991

                                                    1991        ISS     aJNEIITlCII       ELECTRONICS SESSICII      ABSTRACTS

      This    year's     session     at the convention            in       Cobleskill,            This conductivity   technique  shows promise as a way to do
  New York        is   scheduled       for 9:30AM on Monday, July                         1.
                                                                                                  "cave  hunting"   from the surface   with   the same survey
  Informal    show-and-tell     and general discussion     follows                       the      gear.   Maximum horizontal    range is the usual  1500 feet
  scheduled    papers,    so bring your favorite    project!                                      (457 meters) or so, in quiet conditions.


                           BATTERIES       FOR CAVING                                                                    CAVE RADIOS      AND THE LAW

                          Chuck Heller        NSS 6618                                                                  Brian Pease          NSS 7476
      A survey of different        types of batteries         and lighting                               Federal Communications Commission regulations        cur-
 systems for dry caving includes             building     a simple    charg'                      rently allow homebuilt cave'radios     employing loop anten-
  ing system which one can use from AC or car battery.                                            nas to be legally operated in the USAwithout license or
      Costs, advantages       and disadvantages        of standard   D, C,                        approval of any kind. The weak electric      fields    actually
 A and AA cells,         nickel'cadmium       dry and wet cells,          gel                     generated by loops at low frequencies allow cave radios
 cells,       lithium batteries     and mercury batteries          will    be                     to legally operate at much higher power levels (and high-
 covered.                                                                                         er frequencies)     than commonly used. In particular,      this
      Care and feeding of gel'cells           and nickel-cadmium        bat.                      will allow the development of high power two-way voice
 teries,       along with memory-restoration           and depletion       of                     cave-radios      in the optimum 15-30 kHz range.          Units
 ni-cads     will be discussed.        Shelf-lives      of all the above                          offered for sale in quantity are supposed to pass a cert.
 batteries       will be covered.                                                                 ification     test and would carry warning stickers      saying
      An inexpensive     charging    system which is easy to build                                that they must not cause harmful interference,      etc., such
 and can charge all types of batteries               will be demonstrat-                          as those found on cordless telephones.
 ed,     along with examples of different            types of batteries
 and lights.
                                                                                                                       THE RIGHT   TEST    EQUIPMENT

              AN EXPERIMENTAL        SYNCHRONOUS      CAVE-RADIO
                                                                                                                          Ray Cole     NSS 12460

                         Brian     Pease     NSS 7476                                                  The newcomer to caving-related       electronics'may       be a
                                                                                                  little    frustrated  without the right type of electronic
     A synchronous       cave-radio    operating        at 3496 Hz has been                       test-equipment.      The basic tool needed is a method of
developed       and tested      in several      different       applications.                    measuring voltage,       current, and resistance.            This is
 It was originally        built as the simplest            device that could                     called a volt'ohm-milliammeter        (VOM). Useable models can
provide     a steady         meter. readout        of received         relative                  be found at electronics        parts    stores     including Radio
magnetic-field       strength      from an in'cave         beacon to determ-                     Shack.      More sophisticated     equipment including signal
 ine depth by field strength           for survey applications.                The               generators and oscilloscopes       is needed for building your
zero-centered       meter provides       left-right        or up-down       indi-                own cave radios. A good place to find electronic                  test
cations     for     homing      in on "ground         zero."      The phase-                     equipment is at amateur-radio fleamarkets             called      Ham-
sensitive     detector     provides    deep nulls by rejecting               out-
                                                                                                 fests.      Other useful items include electronic              bread-
of-phase      secondary       signals   generated        in the      rock.        A              boards,      and capacitance     and     resistance-substitution
simple     method      of measuring ground conductivity                 without
                                                                                                 boxes.
probes,     using these secondary           signals,      has been      tested.

 .=.=.=.=.=.=.=.=.=.=.a.=.=.~.=.=.=-=.=.=.=-z.=.=.=.=.z-.-=-:-:-:-.-:-:-.-:-:-:-:-:-:-:-:-:-:-:-.-:-:-:-:-:-:-..:-:-:-:-
                                                                                 Io'IIEAT lNP     IIOTES
                                                                      from cavers'         computer-mail   list
    FOR STORAGE:        There is a Rubbermaid(tm)                     food/beverage              The problem      with VLAs are:
container     which is perfect      for the lamp.                     It's     roughly
rectangular,     with a vertical      depression   for                a handle.       It
                                                                                                 1. If you seal them with stainless    sheet-metal    screws,
sits vertically,         with a long,     narrow lid.                   I don't know                they will rupture or explode (depending on charge
the capac i ty;     it's   about 9" C23an] high.                      There are two                 rate)   if you forget to take the screws out. This is
sizes available;         measure your lamp to make                    sure it fits.
                                                                                                    remerkably easy to do, especially    if you put the lamp
You can coil the cord next to the battery                             and put       the
                                                                                                    on charge in those dazed pre- dawn hours.
headpi ece in there too.                                   ..    Phil      CltLn!wick
                                                                                                2. If you try to get by with lots of duct tape, there is
Re: diffusing  lenses:  I've sanded the inside surface of                                          still   the chance that the thing will leak. I was a
clear lenses, and that works very well.    If you give the                                         little  lazy about using fresh tape a while back, and
lens a grain,   you can shape your patch of light!      By                                         had acid allover   my elbow as a reward.
mounting the lens with the grain running horizontally,
you will cast a tall and narrow oval of light.
                                                                                                    Battery acid will destroy nylon, of course,      so there
                                               Bcb Yarshow            --                        are all kinds of opportunities   for disaster when batter-
                                                                                                ies are charged in vehicles, thrown in the back to go up
    I strongly    recommend that anyone buying/replacing        a                               the mountain, backpacked into caving areas, etc.
Wheat battery  consider   a sealed Gel'Cell    instead of vent-                                     To conclude, my two vented Wheats make me very nervous
ed lead acid (VLA).     Kohler does not make a Gel-cell, but                                    and I wish that I had bought Gell-Cells.      Rumors during
Bob&Bob and others carry them at prices similar         to the
                                                                                                1984-85 notwithstanding,     they now seem to be quite
vented ones (made by NiteLite,     I believe).                                                  reliable.                                      '-John Ganter


                                                                                          2
 spelsonica           16
 v. IV no.        4        May   1991




                                               THE STAll LEY ESTIMATCII       All)   OTIER     MISCELLANEWS        RAMBLINGS

                                                                      by Jim McConkey
                                                                                                   *

The Estilllltor                                                                              Ultrasonic   tapes in general

    I have been interested              in ultrasonic   tape measures for                      Ultrasonic      tapes have several disadvantages which I
several years          now.      Several times I have started to design                   have already mentioned. We need to remember that they
and txJi ld one txJt my attempts have always been interrupt-                              work on the same principle as bat's echolocation.                Indeed,
ed by other,           more important projects.          When a local                     bats can easily hear the frequencies these devices use.
hardware store           recently had a sale on ultrasonic           tape                 The transmitted signal is very short,               so they they will
measures for the incredible price of just S12.99, I just                                   just hear a couple 'clicks',          txJt they could be loud. The
had to pick one up and check it out.                                                      use of such devices can conceivably also affect                    their
    What I got was the Stanley "Estimator," a 2 3/4" by 4                                 echolocation and therefore,          flight.     Ultrasonic     rangers
3/4" by 7/8" [70 x 2 x 2_2 cm] plastic case with a large                                  should never be used near bats,              especially    hibernating
ultrasonic        transducer,     an LCDdisplay       and two bright                      ones (txJt surveying should never be done near hibernating
yellow buttons. The unit is definitely              NOTwater (or mud)                     bats, anyway).
proof,     even in its hard belt carrying            case (included).                          The best way around some of these problems is to use
The unit measures 2 to 33 feet 0.1' increments.                                           an active target and direct measurement.                 The Estimator
    Naturally,        I've taken it apart and examined it.            The                 and virtually       all other rangers that I am familiar            with
Estimator       is powered by two button-batteries,            which do                   use echo distancing:          The time the sound takes to reach
not look like they were designed to be replaced (txJt at                                  the target and bounce back is measured. Knowing the speed
S13 for the whole thing,              replacement batteries         would                 of sound through air (roughly 0.9ms per foot [2.95 ms/
probably cost more than a new Estimator,                anyway!) There                    meter],     temperature dependent), the round-trip             distance
is apparently           some sort of custom processor         hidden in                    is easily calculated.        This is divided by two to get the
black epoxy under the LCDdisplay,               maki~g hacking dif-                       actual     distance.     In an active-target      system, the master
ficult at best.          The pulse-sending and receiving sections                         unit tells the slave target to transmit a sound pulse by
are accessible,           though.     The unit sends txJrsts of 14                         light flash, radio or other instantaneous means. The time
pulses of about 48 KHz. The pulses are amplified in a                                     that it takes the pulse to return directly                  gives the
small transformer to several hundred volts before being                                   distance.      This removes the obstacle           and perpendicular
sent to the electrostatic               transducer.      Several pulse                    wall target restrictions.        Also, since intensity falls off
txJrsts are sent,          until the unit gets a steady reading,                          with the square of distance and we are only measuring
though it never seems to do less than about 3. It appar-                                  half the distance now, we only need a quarter                   of the
ently averages a number of readings before displaying the                                 transmitted power (less annoying to bats!) to measure the
distance.      There is no on/off switch. Pressing either (or                             same distance. Conversely, we can measure 4 times farther
both) of the two yellow buttons on the sides starts                   the                 with the same power (actually more, since we have no
measuring.       The unit beeps to tell you when it has a                                 absorption by the target).
stable     distance,       and the distance appears on the LCD                                 I may try to pursue this approach further using Esti,
display.       It automatically         powers off after       about 20                   mators for their transceiver           sections,      and building my
seconds if not used again.               There is a small trimpot                         own optical trigger (which could also double as a photo-
accessible       through a hole in the side,          txJt there is no                    flash slave trigger!)         and counter.      Thanks to the epoxy
mention of what its for.           I would assume it could be used                        covered SMT parts,           I don't think the Estimator can be
to compensate for temperature.                                            .               altered to count twice as fast.            I could rig one with an
     I have taken the Estimator caving several times. One                                 optical     trigger so that I only got a reading of half the
 time I also had a surveying tape along and was able to                                   distance, txJt then the accuracy would only be 0.2', which
compare readings.       Every measurement I took (admittedly                              is not enough for most modern cave surveyors.
 less than 10) agreed to within 0.1'.          I should note that
ALL readings were consistently       high by 0.1',     so this may                        A total      surveying     instruaent
be a temperature calibration       problem. On the last trip, I
tried    it in a room with a large waterfall           (which are                             My interest in ultrasonic      rangers is just part of a
notorious     for screwing up ultrasonic devices)         with no                         pipe'dream      (for now, at least) of a complete point-and-
problems.                                                                                 shoot surveying instrument/data       logger using an active
     For surveying use, the Estimator will, of course, have                               target.     Just set the target, point the device at it, and
the inherent problems of ultrasonic        tapes.    The range is                         the unit would measure distance ultrasonically,         tempera-
somewhat limiting       (though around here, shots average                                ture (to compensate distance),        angle by capacitive tilt
maybe 15' at best) and they are easily confused by ob-                                    transducer,      and bearing by fluxgate magnetometer (Radio
structions
the target.
              (a column, for example) between the device and
                Oh, and did I mention the target must be a
                                                                                          Shack has one on sale for S50 here
                                                                                          this thing yet?) instantly and log it.
                                                                                                                                        -
                                                                                                                                      has anyone hacked
                                                                                                                                       When you get back
wall approximately perpendicular        to the line of sight?    I                        home, dump the data via RS-232 to SMAPS and, voi la,
already mentioned that the Estimator is less mud and                                      instant map! Anyone interested?        Any questions, comments
waterproof     than would be desirable.       While I doubt the                           or experiences with any of these devices are welcomed!
Estimator will find much use in surveying, it seems to be
ideally    suited    to sketching.    Howmany times have you
tried estimating a ceiling height out of reach?            And how
many sketchers      actually measure the distances         to the                                 604' Shirley Manor Road
walls? The Estimator would make this an easy and accurate                                 *       Reisterstown, MD21136.2319
one-hand job.                                                                                     (301) 526.6224




                                                                                      3
                                                                                                                                                                   speleonics      16
                                                                                                                                                  v.    IV   no.     4   May    1991


                                                tEASl8llG    GIIaJ8) aJDJCTIVITY WITI A CAVERADIO
                                                                           by
                                                            Brian Pease    NSS 7476  W1!1t

     In fall of 1990 I successfully   measured the electrical                           lItere:     I is the beacon loop current in ~,
cOr"ductivity    of limestone in eastern U.S., using my \II-                                       A is the loop area in meters squared,
modified 3496 Hz phase-selective      cave radio set.       This                                         2 ,.,. f where f is in Hertz,
work was essentially      a follow-on to Ian Drunnonc:l's art.                                    "'.
icle    in Sceleonics ~ 4 which suggested it as a viable                                           R1 is the distance to the receiver in meters,
                                                                                                   IJo = 47T x 10-7 henries/meter,
method but, being out of touch at the time, I did it
independently     without knowledge of Ian's work, based on                                       6"1 is the condJctivity     of the rock in mhos/meter,
papers by Bamister2,3,      and by Willill1\S and Beming.1                                         Hver is the pril18ry (vertical)     magnetic field,
    Knowing conductivity      of a new area prior     to doing                                     Hhor is the secondary (horizontal)     magnetic field.
                                                                                                   i simply indicates that Hhor is shifted 90
radiolocations     can be helpful in I18king decisions     about                                      electrical   degrees from Hver.
whether to use high or low frequency gear, estimating
sharpness     of nulls for depth measurement, and even cave                         Combining            equations           [1] and [2],         then solving           for    con-
hunting.                                                                            ductivity:
THEORY
                                                                                               Hhor      .506 x 106
                                                                                    tT    =                                   mhos/meter (or Siemens/m,                          [3]
     My technique, like Ian's, is based upon measuring the
 ratio   of the primary (vertical)   and secondary (horizon'                                  ( Hver)                                     to use the
 tal) field strengths at a distance from a horizontal loop                                                                                modern term)
 located on the surface, which transmits         a continuous                          All three equations                      are valid    only in a limited                 range
carrier (see Fig. 1). The equations for these fields are                            as follows:
cooplex but can be expressed in simple quasi-static        ap-
proximations     over a limited range of values.    Note that                       1) The ratio of conduction to displacement curr~nt in the
the two fields are 900 out of phase in this range, which                            limestone must be greater than 10. This is true for the
is the key to the technique.       Hhor is generated by cur.                        nonnel range of radio frequencies      and conductivities
rents    induced into condJctive rock; it "fi lls in" the                           encOU'ltered.
nulls of the conventional depth-measuring process, making
them less distinct with greater distance from the surface                           2)   The maximun allowable                         distance        to the
point directly above an undergrOU'ld transmitter.                                                                                                                   recei ver     is
                                                                                    approximately

  Hver   =-
                    IA
                                     ~/meter;                   [1]
                                                                                                  .506   x 105
                                                                                    r
                4 '1T R13                                                                =
                                                                                              J       C"'1 f
                                                                                                                                                                                 [4]


                IA cr1   ~o(J.J                                                     This       is 68 meters      for         f = 3496 Hz and (1'"= .0031 mhos/me
 Hhor    = -i                     amps/meter                    [2]
                 16 T1' R1




                                                                                                                                    Mtlfsu~E
                                                                                                                             IF""
                                                                                                                                    HHot(              PHA$~'      SlLtlT'VI
                                                    AXIS AIIVIEO      4T       SEACON
 311" Hz                          +----             ---------                                 -----                  -                        REa/viA
 BEACON                                                                                                                                       (JP';/,/fTil'LI '''JSij

                                                .   H HOR
                                                                                                                     I                  MfASUU
                                                                                                                                    'DHVEU
                                                                                                                         I




                                                                   R,      I   METERS-




                                                                        Figure 1.


                                                                                4
    .pel.onies            16
    v. IV no.         4        May    1991

    Steted     another     wey, the limit on maximum      range    for    en                                    The procedure            is    similar to the one Ian proposed for a
    accurate    meaaurement     is Hhor/Hver   < 0.1, which means      thet
                                                                                                             "normal" radio:
    the    primary    field must be at least 20 dB        stronger     than
    the secondary      field.    In this range,    the secondary      field                                 e) Set up the beacon                loop     exactly      horizontal    (or   parallel
    drops     linearly     with distance    and the primary     field     is                                to     the      slope      if measuring            uphill).     It is   operated     in
    unaffected       by    the       rock.    Conductivity       for   greater          ranges              continuous-onmode (i.e.,                     not pulsed).
 can be       found  from the plots   and tabl~                   in   lan's          article,
 which        is indeed  the necessary   method                  when using            conven-              b) Measure a convenient                    distance,
                                                                                                                                                             perhaps 200 feet [60m],
    tional       receivers           (i.e.,   without     phase-sensitive              detect.              or use equation [4] if you have a                  rough guess of the
    ors) which probably cannot measure secondary fields                                  which              conductivity;              .002     mhos/m is a good starting  point in
    are more than 20 dB weaker than the primary field.                                                      Eastern U.S.
 MEASUREMENTS                                                                                               c)    With the receiver loop exactly horizontal   (parallel
                                                                                                            to the beacon loop) al ign the phase for maxinun primary
     With the help of my (very) patient wife Bonnie, I used                                                 signal Hver and record the relative  level.    Nowalign the
 my unmodified cave radio to test the concept.           The meas-                                          phase to completely null the signal.
 urement setup (Fig. 1) consisted of a simple TV-crystal
 controlled beaconof the type used by Ray Cole5,6, and a                                                    d)     Rotate the receive  loop to a vertical    position    with
 phase-selective        (synchronous) receiver controlled by an                                             its      axis      parallel         to the
                                                                                                                                             ground and pointed       at the
 identical     crystal.      The oscillators   were roughly temp'                                           beacon.      This can be done by hand, since only the Hhor
 erature-compensated.         The receiver had a phase-shifting                                             signal     is present.   Record the level of the secondary
 switch for alignment           prior to each measurement, and                                              field.    Repeat c) and d) if necessary.      Phase drift is a
 built'in    means to precisely match the two frequencies                                                   significant    problem, especially   if Hhor is 25 dB or more
 before the units were separated for the measurement.            I                                          below Hver.
 can adjust the oscillators          to nearly one cycle per hour
 (short term) and have achieved better than one cycle per                                                   e)     Take the ratio Hhor/Hver and calculate       the conduct-
 minute after several hours in actual caving conditions.                                                    ivity using equation      [3].    If Hhor/ver > 0.1, then start
 This stability     is adequate for rediolocation     and has been                                          again     with  smaller    transmitter-receiver     spacing.   No
used in caves deeper than 300 feet [9Om] (the subj ect              of                                      correction     for noise is needed, since noise averages.       to
another      article),    however, such stability      is very marg-                                        zero     in a phase detector.      Bandwidth can be reduced     if
inal for measuring        the secondary     field.   The key to suc-                                        jitter     is a problem (I normally use 1 Hz), or you can
cessfully       measuring     the secondary    field (Hhor)   lies   in                                     return on a quieter     day.
the    fact that in the recommended range it is at a phys-
ical     right     angle    to the primary field,      i_e.,    in the                                      Some     results       are shown in Table 1:
physical     null of Hver and also at 900 electrical          phase to
it, i.e.,      in the electrical      null as well.

                                                 Measured Magnetic          I
                                                  Field     Strength                                                                Calculated
                                                                            I                           ILoop Spacing          I
                                                                                                                                    Conductivity          I

                                               Primary        secondarY          Hhorl Hhor-
                                                  Hver           Hhor            Hver I Hver                ft.        mtrs           mhos/mtr                   Cannents
--.. --                     -'" -----+                                      I
                                                                                                               -
                                                       --+-.. ..+-----.+..--.. -+100 -+-. +-..-----.----.+-- hard
                                                                                                        I                      I                          I
                                                                                                                                                                                     -           --
near McFail's             Cave, NY                +60 dB +26 dB ,34 dB .02             30.5  .0031        Hhor                                                            to get.
  ""                "                            +42           +20              .22         .08             200       61             .0031                    No problem.
  ""                "                            +31.5         +15.5            -16         .016**          300       91.4           .0028                    Easier to measure.
near     Clarksville Cave, NY                    +62 *         +30              .32         .0251           150       45.7           .00174                   2 other tests   were identical.
over Clarksville Cave                            +61 *         +22              ,39         .0112           150       45.7           .00076                   10x15-foot passage 60 ft. down
                                                                                                                                                       [3 x Sm]             [20m]
      Receiver gain was increased                   prior     to these tests.                        This    ratio       is slightly          beyond the range for accurate    results.
*                                                                                           **

CONCLUSIONS                                                                                             RECCM4ENDATIONS

    This is an easy way to measure conductivity.     3496 Hz                                                This equipment is actually a large "treasure           finder"
allows measurements at reasonable distances,     at least   in                                          device optimized for detecting variations          in rock con'
the Eastern U.S. Spacing must be accurately          measured                                           ductivity.       For cave hunting, only the secondary field
because conductivity   varies as its square.      This seems                                            need be monitored, since the main field is not affected
like a       great way to check a new cave area for                         conductive                  by conductivity       in this short range. As a rough guess,
overburden without entering the cave. Strongly       conduct.                                           try spacing the receiver two to three times the expected
ive overburden (say, .01 mhos/mtr) can cause errors       and                                           depth of the bottom of the passage.
broad nulls    in depth measurements,    and possibly    even                                               A practical    conductivity-measuring    device should have
ground' zero errors.     There is definite   potential    for                                           a wire line between transmitter        and receiver so that both
"cave hunting" with this device as shownby the measure-                                                 units can share the same local oscillator,         thus eliminat-
ment over Clarksville Cave. This extremely low conduct-                                                 ing drift.      Crystal control would then not be necessary.
ivity was measured perpendicular    to the cave passage but                                             The comecting wire would also act as a measuring tape to
camot be explained       by the small cave passage alone                                                maintain constant spacing.        A digital voltmeter could be
unless   it has "dried out" all of the nearby limestone.                                                used for readout.
There is no obvious joint visible underground or on the                                                     As Ian speculated,       it may be possible to obtain good
surface.     Additional measurements confirmed the effect.                                              results    with an ordinary continuous beacon and conven-
Cave hunting from the surface will be the subject      of a                                             tional receiver by using an audio voltmeter as a readout
future article after I have accumulated more experience.                                                and following       the procedures outlined in his article.


                                                                                                 5
                                                                                                                                                              speleonica 16
                                                                                                                                          v.    IV      no.     4 Kay 1991

The tricky     part is measuring       the secondary      field     where
you must carefully        find the bottom of the null            of the                      2. Bamister, P. "Some Notes on the Utilization of a
                                                                                             Vertical Magnetic Dipole to Determine the Properties of a
main field and then record its level.             I rec:annend trying
                                                                                             Stratified Earth" USL Report 695, 5 Oct. 1965.
this at higher frequency         or greater  distance     than I used,
so that the secondary       field   is only 10 dB or less         weaker
than   the primary.      The disadvantage      of doing so is that
                                                                                             3. Bamister, P. "The Quasi-Static  Fields of Dipole
                                                                                             Antemas - Part 1" USL Report 701, 3 Jan 1966.
then   the   Hhor/Hver ratio begins to vary as the square
root of conductivity,         and so may be nu:h less         sensitive
                                                                                             4. DrUllllOnd, Ian        "Ground Conductivity by Electro'
as a cave-hunting     device.                                                                Magnetic Methods"         Speleonics 12, Apr. 1989
References                                                                                   5.  Cole, Ray "Organ Cave Radio" Speleonics                         3, Fall
-..-..-...--..
                                                                                             1985 (corrections in Speleonics 4).
Author's  address: 567 Fire   St.,                   Oakdale,     Comec:ti cut              6. Stevens, Paul. Caves of the Organ Cave Plateau, WVSS
06370 USA. Home phone: 203-447-9497                                                         Bulletin 9, 1988. Appendix G contains description and
                                                                                            schematics of Cole's equipment.
1. Williams, R. and Benning, C. "Conductivity Measure-
ments of the Earth at ELF" IEEE Transactions on Antennas                                     [Manuscript    received     17 Nov. 1990.
and Propagation May 1963                                                                                                                       -oEd.]


-=-=-=-=-=-=-=-=-=-=-:                    a-=-.-=-=-=-:-=-:-=-=-.-=-.-:                      :-:-:-:-:-:-:-:-:-:-:-.-:-:-:-:-:-:-:-:-:-:-:-..:.:..:-:-


                                                                             SEE NEXT PAGE-'
                          --               --

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                                                              - -
                                                                       "



                                                                               6
    speleonics          16
   v.   IV    no.   4        May    1991


                                                   CAVERS   GET IfAJl)S-(JI    EXPERIENCE IIITH liPS IAYIGATlON

                                                                               Frank Reid
  This   article             was originally      posted   to the     cavers'                longitude/elevation)        fix.    If only three satellites          are
  computer-mailing             list. Here it   is abridged   and updated.                  visible,     the fix degrades to "20"; elevation is not com-
                                                                                           puted, and there is some attendant loss of horizontal
      Global Positioning     System (GPS) is a U.S. military                               accuracy.
  satellite-based   navigation    system, accurate within 25                                   Accuracy varies with a parameter called "POOP" (Posi-
  meters worldwide; special procedures can refine    accuracy                              tion Dilution Of Precision).           POOPis continuously          indio
  to    3-5     meters.            GPSis superior to the older        LORAN-C              cated on the display, and is a funciton                   of satellite
   system, and will be valuable for surface karst studies.                                 position:       POOPis poor if all the satellites            are close
       Ar8ar    Mirza, Randy Jackson.          Larry Mullens,        Bob                   together in the sky; ideal POOPoccurs when three satel-
   Armstrong and Frank Reid attended a 1.5-day GPS training                                lites     are 120 degrees apart in azimuth and about 20
   session sponsored by the U.S. Dept. of Agriculture Forest                               degrees above the horizon,              with a fourth satellite
   Service office     at Bedford, Indiana.          We were invited                       directly overhead. POOP is analogous to "strength of
  because cavers have agreed to help the Forest Service                                    figure" in triangulation.
  make an inventory of caves and karst features on govern-                                     GPS is not usable at all times of day because he full
  ment land, for conservation purposes.             OUr instructor     is
  with a Forest Service engineering             section    in Montana                     "constellation"        of satellites,     providing 24-hour cover-
                                                                                          age, will not be in orbit \IItil 1993, The PC software
  which develops and evaluates new technology.             The Forest                     which comes with the units will produce tables and graphs
  Service is using GPS extensively for land-surveying,               and                  which show windows of good conditions.
  finding    it a very cost-effective       supplement to conven-                              GPS does not work underground:            The satellite       radio-
  tional labor-intensive     optical methods.                                            signals       are about 1.4 Gigahertz.        GPS.is usable under a
      The part of GPS available to civilians               includes a                     full forest canopy.
  "feature" called Selective Avai labi I ity (SA) which intro-                                 We used "TANS" GPS receivers made by Trirrble Naviga-
 duces intentional      errors which degrade accuracy to 100-                            tion of Sunnyvale, California (see Resources column).
 300 meters, ostensibly to prevent an enemy from using the                               The receiver and external 12-volt battery                 corrbined are
 system. Military receivers remove the encrypted error.                                  about the size of two br i cks. The antenna is about. the
      SA was turned OFF when the "Gulf Crisis" began, alleg-                             size and shape of the upper half of a plastic                         "Big
 edly because insufficient        quantities      of military.grade                      Mac"(tm) container.            Its base is threaded to fit a
 receivers were available,      so many civilian-type        receivers                   surveyor's range-pole.           It is also supplied with a magnet
 were in military service. Hopefully, they will be avail-                                for temporary mobile mounting. The antenna should be
 able as war-surplusl       GPS receivers presently cost $2500-                          kept level so that its hemispheric field of view does not
 3500, predicted to ultimately       reach $500.                                        miss satellites        near the horizon.       The antenna should be
     Our instructor     has worked closely with other govern-                            kept about 2m above the groll1d. Reception problems may
 ment agencies and GPS.receiver manufacturers,            and offered                   arise       if deep valleys or tall buildings           obscure satel-
 the prediction     that political    pressure from private         and                  lites, or if the antenna is near a vertical metal surface
 nonmilitary government GPS-users will result in SA being                               which reflects the signals, causing multipath distortion,
 permanently turned off.                                                                the same effect which produces "ghosts" on a TV screen).
     Even with SA turned on, measurements with error radius                                   The Trimble \IIitsare 2-channel receivers:                The sig-
 2-5   meters can be made by "differential              post-processing":               nificance        of rurber of channels is in speed of response
  One GPS receiver is placed at a known location, e.g.,                  a              and illl1U'lity from"deadspots"where                 satellite      radio-
  first-order      benchmark for which GPS coordinates               are                signals       are momentarily shielded,          and from multipath
  known. This "base" unit records its own GPS.indicated                                 problems. A single-channel            receiver must divide its time
  locations (including time) while a "remote" \IIit is taken                            between 3 or 4 sa te II i tes and "housekeep ing" func t i ons
  into the field.         The remote unit records a file of sev-                        (which include looking for other satellites).                        A 2-
 eral minutes of data at each position of interest.                 The                channel receiver is significantly             better than a 1-channel
 base and remote data are slbsequently downloaded into an                               receiver       (e.g.,    the handheld Magellan (tm), which our
  IBM-PC-compatible computer which comperes the remote and                              instructor        does not recommend). Six to eight channels
 base data at matching times, and subtracts             the errors                     are optinun.
 from the remote data.          The base and remote \IIi ts mey be                            The TANS reciever is attached by RS-232cable to an
 separated by as much as 250 miles (4DOIan).                                           Omitech "Polycorder" (handheld general-purpose cOlTputer/
      A "survey grade" GPS receiver is accurate within a few                           keyboard/display         \IIit which the Forest Service uses for
 centimeters.        It costs about 10 times more than ordinary                        many applications).           It stores data, waypoints, etc. and
 GPS receivers.        Some survey-grade receivers contain their                       can be programned, lop/downloaded, etc. independently                     of
 own atomic clocks.                                                                    the GPS receiver.
      Certain nuances and oddities must be observed in using                                 GPS indicates positions to the nearest 0.1 second of
 GPS effectively:         One problem could be called      prolifer.                   latitude/longitude          (about 3.3 meters).            Its internal
 ation of coordinate sy.stems: GPS uses a mathematical                                 resolution is 0.01 second (about 33cm [1 foot]).                          We
model of the earth's shape called IIGS84, which is more                                recorded data once per second (of time) while carrying                     a
accurate than the 1927 model upon which most topographic                               receiver aroll1d the periphery of a parking lot, and were
maps are based. Discrepancies range from negligible                   to              amazed by the detai led computer. plot of our trip.
as much as 200 feet (6Om) horizontally.           It is recommend.                           To survey a point, e.g., a karst featrue, the antenna
ed that GPS coordinates be considered           absolute,      rather                  is placed at the spot and data are recorded once per
than tIcal ibrated" against latitude/longitude        measurements                    second for three minutes.              The file is later downloaded
taken from topographic maps.                                                          to a PC which calculates           the mean location and produces a
     GPS elevation is given in "height         above ellipsoid,"                      scatter. plot of the data with a standard-deviation                  circle
which is different         from sea level; in continental       U.S.,
the ellipsoid       (abovementioned mathematical model) is 16
40 meters below sea level.
                                                                              -       around the mean lat/lon.
                                                                                      of 3-5 meters.
                                                                                                                           We achieved standard deviations
                                                                                                              Data can also be gathered while travers-
                                                                                      ing around an area (e.g., a sinkhole).                The computer can
     Elevation accuracy is usually somewhat less than hori-                           calculate the enclosed area and the mean location of its
zontal accuracy.         Four satellites  must be simultaneously                      centroid.
visible       in order to compute a 3.dimensional        (latitude/

                                                                                  7
                                                                                                                                                                speleonics      16
                                                                                                                                              v.     IV   no.     4    May   1991


     The older       LORAN'C      radionevigation        system    1.18..   grOU'ld-       Glcb8l   Poaitianirv     Syst-        statl.a      report      on 'IN/WVII
 based tranami tters.  I ts repeatable accuracy can some.
 times exceed that of GPS but only in relatively        smsLL                                  WWV and WWVH broadcast reports on the status of the
 regions of favorable geometry relative     to transmitting                                Global    Positioning   System.    The WWV broadcast      is at 14
 stations.   LORAN-C covers most of the U.S. but is not                                    minutes past the hour and is repeated       during the       follow-
 worldwide. Good LORAN-C receivers are nowavailable for                                    ing minute.       The Omega navigation  system     status     report
 less than $300.           LORAN-C      has a resolution of 0.01 minute                    continues     to be broadcast   at 16 minutes past       the hour.
 of lat/lon,  which is about 50x60 feet [15x1~     at mid-                                 The GPS report on WWVH is given at 43 minutes past the
 latitudes.    It is excellent for long trips    and cave.                                 hour with a repeat at 44 minutes past.         This is followed
 rescue operations,   but nonideal  for cataloging    karst                                at 45 minutes past with the solar activity         report.
 features:         LORAN-C       operates at low frequency (100 kHz)
 and propagates     around the curvature of the earth by                                   Richard B. l~ley                   BITnet:        LANGWUNB.CA          or   SE@UNB.CA
 "grolrld wave." Variations in grOU'ld condJc:tivity    (e.g.,
 near sinks and escarpments) cause propagation       anomalies
 manifest as position errors.    Cavers have also discovered                               A WHISTLERHUNTER'S GUIDE by Michael Mideke is a 14-
 that LORAN'Cis unreliable    in very deep valleys.                                        Page    introduction     tOthestudy       of "whistlers"    and other
                                                                                           natural    radio phenomena in the audia-frequency           range,   by
 References:                                                                               a leading experimenter.         It includes   plans for an easy-to-
 .... .... ....
                                                                                           build    portable    receiver.      This is essential    reading    for
                                                                                           anyone     working with cave radio at frequencies            below 10
 "LORAN-C  for Cavers," Sceleonics                  2 p. 12.                               kHz. Available for 52.00 and SASE (with postage                  for 2
 "New LORAN-C  transmitters  to fill                Mid-Continent       Gap"               ounces) from Mike Mideke, Box 123, San Simeon, California
   Sceleonics 2 p. 13.                                                                     93452.
 "The Global       Positioning       System"    Sceleonics        11 p.13.
 "GPS Update" Sceleonics             13 p.6.
 "Radionavigation        System Devleo!JlM!r'lts" Speleonics              p.12.
                                                                   ~ p.~14.
                                                                                                              Battery        awrger        References
 Reprinted     Trimble Navigation           ad, Sceleonics
                                                                                                The July '86 issue of Radio Electronics              maga~ine has a
 ..*...*...*...*...*...*...*...*_._*                      *_._*...*...*...*..              construction        article     for a "Universal      Battery     Charger"
                                                                                           intended for gel-cells.
                                                                                                It uses       a LM317 in constant-current         mode. When the
                  REsaR:ES.       REfEREJfaS,       NEWPRaXJ:TS                            terminal     voltage     approaches   full charge,     it trips     an SCR
                                                                                           that    changes      the circuit      to a voltage        regulator     for
                                                                                           constant-vol     tage tri ckle ("float")       charge.
 CPS Info         from rec.ham'radio,          October 1990                                     See also ~ ! Telescooe magazine,              July 1989, p.97 for
                                                                                           a similar     automatic      gel-cell  charger circuit.
     An excellent    GPS receiver is the TANS from Trimble
 Navigation.    It's very small, low' power, and easy to use.
 Antenna is about 5x5 inches, low'profile        phased array.                                                               Coon Dog      Catalog
 The best part is that unlike some of the models made for
 the boating world (like Magellan), the TANShas an RS-422                                 Nite Lite Co.
 port and transmits latitude,    longitude, elevation, speed,                             P.O. Box 8210
 time, and diagnostic data.     Easy to interface.     I'm put-                           Little  Rock, Arkansas         72221
 ting one on my bicycle for nav, mapping, and security.                                   ph: (800) 648-5483
     Contact the c~ny       at BOO-TRIMBLE or 408-730-2900
 (they're in Sunnyvale).                                                                  Actually     a supplier of hunting equipment, their  catalog
                                                      Steve Roberts          N4RVE        includes WheatCtm) lamps and parts, and other powerful
                                                      Nomadic Research         Labs       l~       and bulbs suitable      for caving. Prices appear
                                                                                          competitive.                  [contributed by R81dy JacltsonJ
For subscriptions         to     ill World magazine, write to:
                                                                                                       Poc:Icet'Sized pH Meters Affordable                      by
P.O. Box 10955                                                                                            NcIr8UIsidized       Pollution-Fighters.
Eugene, Oregon 97440.2955                             or call     503.343-1200
                                                                                              Cole'Palmer is marketing portable electrochemical   test
European offices:                                                                         instruments for less than 5100. In addition to pH meters,
                                                                                          there are similar testers         for sodium, salinity,  and
Unit 4E, Bridgegate Pavilion                                                              oxidation-reduction     potential CORP). There are also con-
Chester Business Park,                                                                    ductivity     and dissolved-oxygen meters C5258.50 and $399
WrexhamRoad,                                        Telephone:  0244-680606               respectively)     and a "Water Tester" which measures pH,
Chester CH4 9QH, UK                                        Fax: 0244.680094               ORP, conductivity       and temperature,   all in a single
                                                                                          instrument for 5121.
    Free subscriptions  to the magazine are available    to
the engineering community; for others the subscription                                    Cole-Palmer Instruments Co.
price is 5S4/yr in the U.S. and 597/yr outside the U.S.                                   7425 N. Oak Park Avenue
    Two GPS receiver suppliers that I have had good exper-                                Chicago, Il 60648           800-323-4340                        or 312-647-7600
iences with are:

Trimble Navigation                                                                                      I.t1derw8ter    ec        icatiGn8         Reference
Sunnyva l e, CA                                     telephone:     BOO-TRIMBLE
                                                                                              The January 91 issue of the IEEE journal of Oceanic
Ashtech                                                                                   Engineering   was a special issue on ocean acoustic     data
390 Potrero Ave.                                                                          telemetry (Volume 16, Number 1 ISSN 0364.9059)
Sunnyvale, CA            telephone:       800-229-2400 or 408-737-2400                                --Dale 0IaY8 (daleQlamont.ldgo.columbia.edu)

                                                                                      8
  speleonics         16
  v. IV no.      4        May   1991


                                           EARlY ADY~S        II IJI)ERGR(UI) RADIO CXlIUUCATICII

                                                      by Angelo I. George, NSS 7149RF
                                             1869 Trevilian    ~y,      Louisville,       Kentucky   40205
  IntrodJction                                                                 with the advent of induction cave' radios,     and perhaps
                                                                               later   with U.S. Navy developments used in the detection
      Communication without wires, that was the dream of                       of submarines and in military communication using the
  early    inventors.   With ~rstanding      of electromagnetic                same principal.
  waves, radio grew out of induction and ground.to.ground
  experiments of Nathan B. Stubblefield       in 1892 and Nikoll               Endless CaYems
  Tesla in 1893. Reid (1990) has profiled in part the ac.
  complishments of Stubblefield.       By 1913, the principal of                      Two postcard     views   from Endless Caverns, Virginia,
  inductive communication was being popularized in a child,                   depict     radio operation in the cave. Both of the cards
  ren's electronic    book by Alfred P. Morgan (1913, p. 290.                 show a place in the cave called The Arctic Circle.          For
 295). All were then hi-tech toys beyond the reach of most                    successful      radio reception, the cave passage must be
 people. Commercial broadcast radio started in 1920. Soon                     highly fractured,      very close to the surface, adjacent   to
 after,     radio receivers became a household appliance.                     a valley wall, or a combination of these criteria.         Some
 There were more radios than indoor plumbing in homes                          information has been collected to better target a period
 (Archer, 1938).                                                              when these experiments were conducted.
     Experiments were conducted in faraway places to dis.                          The Rotograph Company of New York published a sepia-
 cover the range and effectiveness         of radio reception.                tone card of The Arctic Circle (Gordon L. Smith, personal
 Some of these experiments          were conducted in         caves           communication,       1 January 1990). The Arctic Circle view
 (George, 1988). Since that article,        new information      has          was available for sale in the gift shop in 1925. The view
 been assenbled       on Endless Caverns, Carlsbad Caverns,                   shows an artist at work rendering a cave scene. To his
 Wyandotte Cave, Fishers Cave, Meramec Caverns, Howe Cav.                     right    in the foreground is a radio set,        curved horn
 erns,    Hudson River Tunnel, and several          international             speaker,     and large square antenna mounted on a wood
 sites.                                                                       frame. The caption reads:
 Hudson River        T~l                                                                                 THE ARCTIC   CIRCLE
                                                                                          Endless Caverns,               NewMarket, Va.
      In January 1924, radio.wave penetration             experiments
  were conducted in the south tube of the Hudson River                                 Making a scale Model of one of the rooms in the
  Tunnel. The experiment was the outgrowth of a request                                Endless   Caverns.    With this model and with color
  made by Morris M. Frohlich, secretary of the New York                                sketches  as guides a large group was constructed    for
  Tumel Conmission.          Frohl ich wanted to know if radio                         the Geological    Hall in the Milwaukee Public   Museum.
  transmitter     could be used to communicate with workmen                            The Radio set keeps the artist       in touch  with  the
  underground in case of an accident               or danger during                    news of the day down here 300 feet underground and
  tumel construction        (Anon. 1924a).                                             over I mile from the entrance.
      The site was located over 1000 feet (300 meters) from                                                               Photo by Merl LaVoy.
  the south entrance and 80 feet (24m) below the surface of
  the Hudson River.       The project was under the direction of                 Merl La Voy was an early nature and adventure photo-
 pioneer radio engineers G. Y. Allen and G. L. Beers of                      journalist.  He joined the Explorers Club in 1923 (Russell
 ~estinghouse      Electric      and Manufacturing    Company. They          Gurnee, personal written communication, 13 June 1989),
 used "a six.tube loop receiver" (Anon. 1924ab). Alan S.                     and accompanied the second expedition of the Explorers
 Douglas, antique radio historian           (personal communication,         Club into Endless Caverns on the evening of 25 May 1925
 6 December 1990) said "the radio that ~estinghouse              used        (Anon., 1925d, p. 12). This was not his first trip        into
  in 1924 appears to be a prototype of the superhet              that        the cave. Apparently he was then living in New Market
 they had just helped to develop for RCA..." The radio                       (Anon., 1925d, p. 12) and as a result was able to photo.
 used a small, square directional           antenna.                         graph the Milwaukee Museumartist at work making wax
    The Westinghouse radio received the following stations:                 models of cave formations.     His photographs would appear
WOR, Newark; WEAF,WHN,and WJZ, NewYork (Anon. 1924a,                         in the Milwaukee Journal, Popular Mechanics, and Endless
p. 1224, 1327).                                                             Caverns brochures and postcard (Anon. 1925cd).
     Frohl ich said (Anon. 1924a), ''We are working on a                         Between 16 and 24 April 1925, Merl La Voy took his
portable      sending.set      for the use of those engaged in              Crebe Radio into the cave "and the Milwaukee museum
dangerous underground work... It has now been proven that                   members, though 240 feet below the earth's        surface had
 radio waves can enter anywhere, and the only thing now                      'music with their work'" (Anon. 1925d, p. 12). This was
needed is a portable transmitter."                                          not I pllmed radio experiment; it was done on the spur
     The realization      of this underground portable transmit.            of the moment for entertainment.
ter was exceptionally            slow in development.    The U. S.              La Voy used a Synchrophlse radio manufactured in 1925
Bureau of Mines did transmission and antema              experiments        by the A. H. Grebe Company. The circuit is tuned radio'
 in mines during 1924 using the "wi red, wireless principle,                frequency.   A six. volt storage battery supplied power to
which makes use of the mine trolley and eliminates                the       vacuum tube filaments.      Several dry'cell  batteries   sup'
need for high'powered sets" (Anon. 1925a, p. 149). From                     plied plate voltage (Lauren A. Peckham, personal communi,
photographs in f.2e:!!.!!: Mechanics, the transmission device               cation, 25 May 1990).
is a room.sized base station             needed                                 Seven hundred feet of motion picture film were shot in
for surface.to'underground           voice communication.    From a         the cave, using white magnesium flares for illumination.
practical     point of view, I must presume these experiments               The film shows part of the Explorers Club expedition,        an
were not very successful because Eve and Keys were still                    old, time square dance in the Ball Room, and the artist
working on the transmission and reception problem in June                   with radio in the Arctic Circle (Barrett,     1925).
1929 in MammothCave (George, 1988). The technique                 did           A second radio postcard has proved very elusive and is
not become practical        until the late 1950s and early 1960s            called Radio Underground. It was issued by the Albertype


                                                                        9
                                                                                                                                                             speleonics      16
                                                                                                                                           v.     IV   no.     4    May   1991

  Company, Brooklyn, New York. This is a hand colored view
  showing    three men with earphones,       four or five boxes      of
  radio   eqJipment,     and a square directional     antenne.     Most
  of the equipment       is placed on a folding     field-table      in
                                                                                            Bob Addis (personal oral call1lJnication 27 May 1990)
                                                                                        told me of an experiment conducted in HoweCaverns, New
  front   of the operators      who are seated    on straight-back                      York. The radio site is located to the left of the ele.
  chairs.   The photograph      is taken at the entrance        to The                  vator shaft about 200-300 feet (61      91m) in the undevel-
  Arctic Circle.     Caption on the beck of the card reads:                             oped part of the cave. He said there - was I lot of wire or
                                                                                        chicken wire strung allover     the place.   The experiment
                     ENGINEERS      TESTING RADIO RECEPTION                             may have been related to national defense prior to I/orld
                                      UNDERGRaJND                                       War II.     ArTf information on this event would be most
               Endless      Caverns                  NewMarket, Va.                     helpful.
                                                                                            Alive   radio broadcast over WGY  was on June 28, 1948
           Far below the surface and nearly a mile from the                             (Cudnore, 1990, p. 146). This broadcast conmemorated the
           Caverns     Entrance redio reception    from distant                         one millionth visitor to the cave. I must presume tele-
           stations    was excellent. Musical reception proving                         phone cable connected to the radio studio for this event.
           exceptionally    good.
      Gordon L. Smith (personal call1lJnication,   1 JarAJary                           ~tte            Cave
  1990) has been able to establish that the radio postcard
  was issued at the cave in 1928. The radio equipment looks                                 George F- Jackson (1970, p. 6; 1975, p. 26) wrote
 older.    Anon. (1926, p. 24) in a promotional     brochure                            extensively  on the lore and exploration    in Wyandotte
 shows a newspaper photograph of th i s same experiment.                                Cave. He reports about the first radio reception   under-
 With no date for the two newspaper items, no clear                                     ground in a cave. This was supposed to have been either
  information is available as to when or why the experiment                             in 1926 or 1927. The radio reception site is in the south
 was conducted. More research is needed.                                                end of the cave knownas the Throne and Canopy. WHAS in
      The Explorers Club mounted another expedition   on 30                             Louisville,   Kentucky, came in loud and clear.     The site is
 October 1940. Well prepared with men, telephones,    ropes,                            highly decorated    with formations  and the passage is close
 candles, balls of twine, and confetti (to mark the way),
                                                                                        to the valley walL. This then is one of the.. criteria
 the expedition was underway. Cowling (1947, p. 42-43),                                 needed for good radio reception     underground.
 the expedition leader remarked:
                                                                                            The radio used was a Radiola model 20 manufactured          by
       The       portable        telephone      equipment    -    which    we   had
                                                                                        RCA in 1925. Lauren A. Peckham (personal
                                                                                        25 May 1990) said:
                                                                                                                                         communication,
       carried         as a contact          with   the outside    world    -   was
       heavy so we left it behind as soon as we were
                                                                                                 The circuit   is a tuned radio-frequency      type with
       certain    that,    if necessary, we could contact     the                                regenerative detector.
       outside    world. We used the eqJipment several     times                                 The Radiola 20 set used tubes of special design (at
       to communicate with representatives     of the press and
       redio, but luckily we never needed it because of any                                      that time) with filaments that could be operated
       emergency. Lowell Thomes spoke to each of the                                             with dry'cell  batteries.    This was a big advantage
                                                                                                 over storage batteries    which had to be recharged and
       members of the expedition in our location far,        far                                 were heavy and messy.
       underground and commented on these unusua leon-
       versations       in his October 30 coast to         coast                            The     first      radio   reception     was        actually       in    Mammoth
       broadcast.                                                                      Cave.       This was made on 19         August      1922 (George, 1988,             p.
                                                                                       5; 1990, p. 6),          four or five       years   prior       to the Wyandotte
  It is not clear if this was a remote broadcast via tele-                             Cave    event.
 phone lines from the cave to the surface, or if Lowell
 Thomas was actually at the cave or in his radio studio.
 The Explorers Club Journal says (Anon. 1940, p. 3):
     Many ex~les    of stalactites, stalalJllites    and calcite                       Fishers     Calle
 formations    were taken out of the new sections.       Sane of
 these are being sent to Lowell Thomes in hopes that they                                   Radio was used as part of a P'bl i ci ty stunt to
may find a spot in his fireplace.      Lowell Thomas carried                            increase    visitation   to Fishers Cave in Franklin County,
an item about the expedition on his broadcast the first                                Missouri. This occurred on Deceneer 2, 1928 (Anon. 1928;
night and that created universal interest         in our work.                         Weaver and Johnson, 1977, p. 63). Lester B. Dill had the
                                                                                       concession at the cave, and he devised a radio-reception
     The Explorers £lYe Journal implies that               Thomes                      event to increase tourism to his cave and at the same
gathered his news over telephone lines and reported later                              time garner sane free advertisement. He obtained a radio
the substance of his conversation with the underground                                 expert by the name of L. E. Johnson from Sull ivan. About
adventurers.     Anonymous (1940) suggests thi s was not a                             one quarter       of a mile (400m) from the entrance at the
true remote radio broadcast as in those conducted from
MammothCave and Great Saltpetre Cave, Kentucky (George,                                Ball roan,     the Johnson-Dill       party    received   "clear,
                                                                                       distinct       reception,    entirely     free from static      or
1988, p. 7).
                                                                                       interference      of any kind," according       to the Sullivan
Carlst.d     Cavern                                                                    ~.
    One of the few successes of Frank Ernest Nicholson's
15-man expedition to Carlsbad Cavern was a radio experi-
ment conducted in the cave. A radio test was conceived by
                                                                                           Sometime after the successful Fishers Cave radio re-
Eric Palmer to gauge "the penetration       of the earth's                             ception, Lester B. Dill tried the same advertising    stunt
crust    by radio waves" (Hall iday, 1976, p. 125; 1981, p.                            in Mer8llec Caverns (Weaver and Johnson, 1977, p. 83). He
2; Nicholson, 1930). At the end of the first      expedition                           had L. E. Johnson bring his new portable     Zenith radio
day on 20 February 1930, the experiment was declared         a
                                                                                       into the cave. On a Sunday with perhaps ninety people in
success.                                                                               the cave, good radio reception was made throughout the


                                                                                  10
   speleonic8              16
   v.    IV     no.    4        May       1991

   cave. The best reception was in high. level passages such
                                                                                              REFERENCES
   as the Wine Room. At present,       I have not been able to
   assign a date to this event.
                                                                                           Anonymous 1924a. Radio Waves Picked up Eighty Feet Under
        An undated photograph in the book, Meramec ~                                            ground. Radio News, 5: 1224, 1327.
  Legendary Hideout
                      2! Jesse James by Dwight H. Weaver and                               Anonymous 1924b. Radiograms World News Happenings Briefly
  Paul A. Johnson, shows a radio broadcast in progress from
                                                                                                Phrased for Our Busy Readers. Radio World, January
  the Ballroom.     This is station KMOX, St. Louis,       (a CBS                               19, 1924, p. 9.
  affiliate)   in commemoration of W. R. Wills Day in Meramec                              Anonymous 1925a. Radio to Rescue Entombed Miners.
  Caverns. Lester B. Dill's    "Meramec Caverns Official      Car"                              Popular Mechanics 43 (1): 149.
  can be seen in the background.        This may place the date                            Anonymous 1925b. The Explorers Club Journal,  6 (1): 12.
  of the photograph between 1939-1942 era.          As in other
  remote cave broadcasts,      telephone lines    connected    the                         Anonymous      1925c. "Underground Cathedral is Reproduced
  cave site to the transmitter     and the distant studio.                                 in Wax," Popular Mechanics, reprinted         in brochure of
                                                                                           Endless Caverns.
                                                                                           Anonymous      1925d. "Museum Adds Cave Exhibit,"         Milwaukee
  International                                                                            Journal, 24 May 1925, p. 12.
                                                                                           Anonymous      1926. Exploring the Endless Caverns of New
        Arthur        L. Lange (1959,             p. 5-6) reports   on some early          market. Virginia.    The Nomad PUblishing Company, Inc., New
  European cave radio                     experiments.   He says:                          York.
                                                                                          Anonymous       1928. Sullivan News, (Sullivan,       Missouri),
          In Poland, DOborzynski received nearby stations              in                 December 6, 1928.
          shallow limestone caves (Hochfreouenz-technik.            Band                  Anonymous 1940. The Endless Caverns Expedition. The
         47, s. 12-13. 1936). The most extensive experimenta-
                                                                                          Explorers Journal, 18 (4): 2-3.
          tion   was done by the Bohemian physicist        Fritsch    in                  Archer, Gleason L.       1938. History of Radio 12 1926. The
         the 1930's,        when he not only received         long-wave                   American Historical     Society,    Inc., New York.
         signals      underground, but also utilized       electromag-
                                                                                          Barrett,    S. A. 1925. Unpublished letter         to Maj. Edward
         netic     transmission      to locate new regions      of the                    M. Brown, dated 13 May 1925. Manuscript          Department,    Mil-
         Punkva-, Mazocha-, and Balcarhohlen of Czechoslovak.                             waukee Public Museum.
         ia, by interpreting       the attenuation   of the radiated
                                                                                          Cowl ing, Herford Tynes        1947 "Mountain Cl imbing Under-
         field      over known spacings         of transmitter       and                  ground or the Third Expedition."         in Mountain Cl imbing
         receiver,     and by measurements of antenna capacitance                         Underground    in the Endless    Caverns   of ~    Market. Virgin-
         along surface        traverses (Beitrage
                                                      !Yr Angewandte
         Geophys i k, numerous papers between 1934 and 1944, et                           ~ Endless Caverns, Inc.
                                                                                          Cuctnore, Dana D.      1990. The Remarkable
         al).                         -                                                   Story. The Overlook Press, Woodstock, New York. ~      Caverns
                                                                                          George, Angelo I.                  1988. Early
                                                                                                                               Radio Experiments    in
 Conclusion
                                                                                          Caves.       Speleonics,      5-8.
                                                                                                                         3 (2):
       In retrospect,    few of the radio reception events were                                                  1990. Great Moments in Early Cave
                                                                                         Radio Experiments.    Speleonics    ~, 4 (3): 6.
  actual experiments designed to test the limits of broad.
                                                                                          Halliday, William R.      1976 DePths of the Earth: Revised
 cast wave penetration           of the earths      crust.      Most were
                                                                                         and Enlarged, Harper and Row, New York.
 publicity      stunts    designed      to attract       tourists      to a
  respective     commercial cave. Merl La Voy took his                 radio                                        1981 Radiocommunications in Ape
                                                                                         Cave, Wash. Washington Speleological Sur., Bull. No. 16,
  into    Endless Caverns on a lark to entertain                  Milwaukee
                                                                                         reprinted   in SDeleonics,   1 (1): 5-6.
 Museum artisans.
                                                                                         Jackson, George F.       1970. First Underground Radio Recep-
      The fOllowing       appear to be true        radio    experiments:
                                                                                         tion. NSS ~,       28 (1): 6.
 Hudson River Tunnel; radio engineers in Endless Caverns;
 perhaps the military(?)         experiments i~Howe Caverns;             and                                      1975. The Story of Wyandotte                                 ~.
                                                                                         Speleobooks, Albuquerque, New Mexico.
 the work of Eve and Key in MammothCave. Internationally,
                                                                                         Lange, A.     1959. Gubser, Max. Untersuchungen       uber
 similar work was being done in Poland and Czechoslovakia.
                                                                                         Radio-empfang   in Holloch (Schweiz).     Die Hohle. Jahrgang
      I welcome any additional         information    on early        cave.              9, Heft 2, s. 33-35, Juni 1958. Cave Notes, 1 (2): 5-6.
 radio activity,      especially    from international        sites.
                                                                                         Morgan,       Alfred P.             1913. The ~           Electrician.       Lothrop,
                                                                                         Lee & Shepherd Co., reprinted   1957.
Acknowled!Pent
                                                                                         Nicholson, F. E.   1930.    The Exploration                            of Carlsbad
      Ms. Judith Campbell Turner, Museum Librarian,           Milwau.                    ~,            Bailey     Printing      Co.,     Wichita      Falls,      Texas.
                                                                                         Reid, Frank             1990. Voices          from the Past.           Speleonics          ~,
  kee Public Museum proved invaluable          in supplying informa.
                                                                                         4 (3): 5.
  tion   on the museum expedition         to Endless Caverns.     Mr.
                                                                                         Weaver, H. Dwight; and Paul A. Johnson                                1977. ~
 Russell Gurnee produced a number of items on the Explor-
                                                                                         Caverns Legendary Hideout of Jesse ~.                                  Discovery
 ers Club expedition         in Endless Cavern and background
 references on Merl La Voy.. Mr. Gordon L. Smith shared his
                                                                                         Enterprises,           Jefferson City, Mo.
 knowledge on postcard views and his collections            on End.
 less Caverns.     Ms. Emily-Davis Mobley supplied the radio
postcard by Merl La Voy. Mr. Robert Addis recounted               the                    -:-=-=-=-=-=-:-a-=-=-:-=-=-=-:-=-=-=-=-=-=-:-=-=-=-:-=.:.
 Howe Caverns radio experiment.          Ms. Lauren A. Peckham of
 the Antique Wireless Association           provided much informa-
t i on on radi 0 types used in Endl ess Caverns and Wyandotte
                                                                                         Fun facts:
Cave. Mr. Alan S. Douglas, a radio historian,              was very
influential     in providing    information     on the Hudson River
Tunnel experiment         and other information      on the under.
                                                                                                   +                                      --.-.--..                        +
ground experimental         use of radios.       Mr. Frank Reid is                                       Manufacturing one kilogram of calcium
                                                                                                   I     carbide    requires approximately three
thanked for       suggesting this series of articles         on the                                                                                                        I

early use of radios in caves.                                                                      I     kilowatt-hours    of electricity.
                                                                                                   +.. . - .. .. .. . - .. .. .. .. .. .. ..                            I
                                                                                                                                                          .. . - .. -. .+

                                                                                    11
                                                                                                                                                                       spe.leonics      16
                                                                                                                                                      v.   IV    no.     4   May     1991



                                                                   REJUVENATING SEALED lEAD-ACID                 CEllS

 \,!ARMING: The following  procedure                     appears dangerous           and        a large power-resistor       for the purpose.         Finally,     charge
 has not been tested by the editors                     of Speleonics.                          the cell at C/10 again for about 10-12 hours
                                                                                                    You must do this procedure          to each individual      cell-     I
 From computer newsgroup sci.electronics,       3 Dec. 1989:                                    usually do them in batches.           The reverse-charge       procedure
 ermi lye@oswego.oswego.edu    (Jon R. Vermilye) writes:                                        can be done assembly-line          style.      I use a 5-volt      linear
 >Has anyone tried to charge long-dead       lead-acid   batter-                                supply.    It adjusts    down to the -2.5 volts needed.              I can
 >ies?      I have a batch of Gates 6v 2.5 amp-hour       sealed                                charge   several      in parallel.        This impl ies,     of course,
 >batteries    made up of three D-sized cells.                                                  breaking     the pack apart.       If you don't want to do this,
                                                                                                then you have to do one cell at a time.
      Depending           on just Hey dead they are,                 I have a tech-
 nique
  following
              that works most of the time.
                    technique,
                                                             In order to use the
                                    you must be able to access each cell
                                                                                                    I've also had to replenish
                                                                                                cells.   To do this,
                                                                                                                                        the electrol     te in very old
                                                                                                                          remove the metal she l around the        y
                                                                                                battery.   There is a nice molded plastic case underneath.
  individually.              IMPORTANT:This procedure                is very stress-            There is a black rubber cap between the terminals.         This
  ful. You must be cautious                and monitor         our progress        care-        is the vent/pressure-relief.       If you remove this cap you
  fully.         I have blown the vents on eel Ys before.                        Safety         can access the electrolyte.      I use a hypodermic need ( e to
 glasses        are recommended.                                                                 inject distilled        water and/or battery          acid into the bot-
       The equipment needws is simple,                   a power supply capable                 tom of the cell.            This procedure       is necessary        to get to
 of delivering             between 20 and 40 amps at about 12 volts.                            the bottom of the dip tube that runs the length                           of the
  It should NOT have foldback                  regulation.         In other      words,         cell.
  it     should        deliver    the rated current           even to loads          that             If the battery       has simply been float-charged               to death,
 pull       the voltage           down to 3 or 4 volts.                    Old linear           it likely needs only disti lled water.                  If the battery           is
 computer power supplies                are great for this.             You will also           heavily      sulfated       from sitting      discharged        for long per-
 need an ammeter to monitor progress.                                                           iods, some acid will help rejuvenate                 the cell.
      Connect the cell                 to the power supply with REVERSE                              NOTE:     I've been told by a friend who works for Gates
 POLARITY.             The cell will initially             draw a small current,                that I'm crazy,         reckless,     and have a death wish for doing
dependent           on the age of the unit.            The current         will rapid-          this procedure.           I suspect he is speaking for the corpor'
 ly increase           to the limit of the supply.                You MUSTmonitor
                                                                                               ate lawyers.         Nontheless,       note that this procedure pushes
 the cell for heating.                 The best way is to hold it in XJr                       a lot of energy very rapIdly               into a small         container.       If
hand.         It will typically            start    heating      in about 30           -c.      the cell pops, it COULD spew acid around the room. I use
onds.        Continue reverse-charging               until     the cell is L-ty                a lab apron and safety glasses,                though the most I've ever
warm (perhaps                110 degrees F (450C]).             Do not cont:nue                seen      is the safety         lift with a nice           little      fart-like
beyond          this.      Heating is greatest          a~ the center and the                  soU1d :-)
thermal           cOnductivity       is low. Therefore            the      temperature
will continue            to rise after you remove power.                                             I'm using        several     Gates packs around the shack here
                                                                                               that are very old.            One set is in an old Motorola Packset
      Let the cell cool for a while,                        then      forward-charge           radio      and is well over 10 years old.                 These have been
with       about        10 amps for 2 or 3 minutes.                 Then short        the      shocked at least twice.
cell.        The cell will still              have a high internal             resist-               On the other hand,           I've had some that simply resisted
ance,        so current           will be small.            ~hen the discharge                 ALL treatment.            You could slag 'em and they'd                still     be
current        is near zero, repeat the above process again.                                   dead. But you have little              to loose in trying.
      This        time,     you should see the reverse current                      rise            A good source of likely subjects                are alarm and emerg-
almost immediately              to the limit.        The battery         is in pretty          ency-lighting        companies.         Both systems use these batter-
good shape by this point.                                                                      ies for standby and are typically                changed on a scheduled
     Apply an equalizing              charge to the cell at C/10 for at
                                                                                               basis.
least        15 hours.         Then discharge        the cell at its rated               C                                                             John De An8Dnd,           WD40aC
(typically           5 amps for the type cells you mention).                      I use
                                                                                                                           Radiation       Systems,      Inc. emory!rsiatl!         jgd

/\0/\    /\0/\    /\0/\     /\0/\    /\0/\     /\0/\    /\0/\    /\0/\     /\0/\    /\0/\    /\0/\      /\0/\    /\0/\    /\0/\   /\0/\     /\0/\     /\0/\     /\0/\    /\0/\     /\0/\



                                                                    EARTH-DIPOlE         aJMJNICATI<Jt          MOTES

[Adapted     from articles    on              usenet       computer        newsgroup               Try using forks or shovels                    as the ground       electrodes
rec.ham-radio,    9-10 September              1990:                                            (they    have a larger surface                area so reduce the coupling
                                                                                               losses).    During World War 1,                 rifle   bayonets were used as
Subj:                    cati
         Ground cOll111.Jni ons.                                                               the electrodes,      and 'spark'                transmitters    using     rotary-
                                                                                               wheel interrupters    generated               the signal.
      Get the stakes as far apart as possible                at both      the
transmitting         and receiving     ends, so as to maximize            the                  G6101B   J                Pete lucas       PJMlQUK.AC.NWL.IA              0793-411613
area of soil energised.           Wet soil is best. Make use of any
local      features       (like ponds, streams,      swamps) to get          a
good low- impedance comection.                 If OU are after         voice
CO/l1llS, consider          using a power osci l Yator and modulating                              I've    done earth'dipole        experiments      using     a 200-watt
                                                                                              cop-car amplifier,        with a 400Hz Variac (tm) for matching.
this,    as you will get greater          range. Try something aroU1d                              I once connected        a pai r of ground rods to an audi 0-
60 to 80kHz.                                                                                  frequency       spectrum     analyzer,       to look at the              60-Hz
     FM is probably best. Beware of harmonics of TV scan                                      hannonics.       The strongest      hannonic is 180 Hz, probably               a
oscillators,         switched-mode     power units,     etc;    these    are                  3-phase      effect.      The harmonics extend            into    ultrasonic
horrible      rasping noises!       If using a PLl detector,        you may                   frequencies,       but the strongest       are below 600 Hz. A high-
find     that it locks to one of these nasty noises                 Instead                   pass filter      which cuts off at 600 Hz works well for sep-
of the intended         signal.                                                               arating     hum from voice.       Cutting off at 600 Hz eliminates
     If you use AMwith the oscillator,              consider    using a LF                    a band of voice frequencies              called     the    First     Formant;
communications        receiver    as the detector.      Some ex-military                      characteristics         which identify       individuals'        voices     are
radios go down to 60KHz. Alternatively, a phase-lock-loop                                     lost, but intelligibility           remains.
(NE565) does a good job with FM.                                                                   Some LF/VlF experimenters have developed a mi~ro-
     If you use raw audio rather    than a carrier-based                                      processor' based adaptive         filter    which samples the ambIent
system, a receiver notch filter to take out the local                                         60Hz waveform and makes a replica                  180 degrees        out of
mains frequency can help. Alternatively,   use a high-pass                                    phase. I t can reduce hum by 50 dB.
filter   to remove frequencies below about 300Hz. I have
got about 3/4 mile with 60 watts (TV sweep-tube)    and a                                      Frank Reid            \J9HKV            reidG)ucs. indiana.edu
commercial receiver.



                                                                                        12
                                                                          PIDE      PATCH     Fmi   HANDHELD           RADIOS

                                                                                             Frank Reid


                                              sw
                                                               .
                                                            1 0 uF 200v
                                                          nonelectrolytic
                                                                                                                        5k mic level       adj.
                                       <-\                          I~                                         (                           ptt
                                                                                )    (-'-)                     (
                                       phone line
                                                                                                                                J          _I_
                                                                          1k)        (8             8)         (1k              \-         0 0         .
                                                                                )                        )     (                /                   to radio   ext mic
                                                                                )   (-                         (
                                       <                                                                                        I                      >
                                                                                              -,-
                                        Transformers:                                                              > to radio receiver
                                        Radio Shack 273.1380                                                         earphone jack
                                        1000 : 8 ohms                                                              >

           This phone patch for the Icom IC.2AT family of hand.                                              The phone patch described above was used very effect.
       held transceivers          was described          in an article        In 73 maga.                ively with field phones during the King BlaIr rescue
       zine      several      years ago (unable to find               referenc-e).          It           (Bloomington,     Indiana(  1990). I recommend it for all
      works with many other radios which key their transmitters                                          cave-rescue communicatIons specialists.
      by completing           a dc path through the microphone;                    a sep.                    When the patch is engaged, the radio operator    listens
      arate       push. to-talk       (ptt)     line can be provided            for     base             and talks     through the telephone handset.    I added an
      and mobile rigs.              The phone patch works with                 commercial                extra set of miniature and subminiature      jacks on the
      telephones           and military-surplus              field     phones.           Two             patch housing so that I can attach a speaker-mike and use
      patches and two radios can relay cave-phone                        traffic        into
      distant      commercial
           The parts
                                    lines.
                              are widely available,            and the circuit             is
                                                                                                         the radio normall with the patch attached.
                                                                                                         beneficial                  y
                                                                                                                         to inc ude an attenuator
                                                                                                                                                         It would be
                                                                                                                                                       pad (about 10 dB) in
                                                                                                         the    line     to the earphone jack, so that         a comfortable
      si~le       enough to describe            verbally    cy phone and improvise                       speaker     level does not over-drive      the phone line.
       in the field.          Something similar           was used in the widely.                            Phone patch operator's      note:    If the person on the far
      publicized        rescue at lechuguilla             Cave in April.         We hope                 end of the phone line does not talk loud enough, lowering
      to report         further    details        of the communications            aspects               the receiver      volume will make him talk louder.
      of that rescue.
           The center       taps of the Radio Shack audio                  transformers              References:
      are not used.           The capad tor blocks de and low. frequenc.,                                .... .... ....
      ringing       voltage.        If the capacitor            is omitted,           field
      phones       will not ring while the patch is engaged                        because               1. "Cave Rescue COIImJnications" Speleonics ~ p.6ff.
      the     transformer        will shunt ringing          current.        On commer.
      cial      (conmon battery)           lines,    de through the' transformer                     2.       "Phone Patch           Connects     Cave to Hospitals"      Speleonics
      will      cause
      core may saturate.
                           an off.hook        condition,     and the         transformer
                                                                                                               Z p. 17.




    SPE~EONICS
                                                                                                                                                                         Bulk Ra te
- P.O. Box 5283                                                                                                                                                    u. S. Postage
;> Bloomington,
J
---
    USA
                          Indiana
                     47407-5283

                            ~'....
                                   r"
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