QRZ News Publication - QTH by pengxuebo


									                                                          QRZ NEWS
                                                A MONTHLY PUBLICATION OF
                                      SOUTHERN PENNSYLVANIA AMATEUR RADIO CLUB, INC
                                            PO BOX 1033 - LANCASTER, PA 17608-1033
                                                                    (Founded June 1960)
                                            AN AFFILIATED SPECIAL SERVICE CLUB OF THE ARRL, INC.
                                                          “Public Service through Communication”
                                                                 Website: WWW. K3IR.org
                                                                Email address: k3ir@arrl.net
                                           Repeaters: 145.230 - 449.975 - Packet 145.030 - ATV 923.250, FN10se
                                       Club site 1715 Breneman Road, Rapho Twp. ( Manheim P.O. 17545 no delivery)

                                            March 2012

President’s Message                                       aircraft, operated into and out of the same
                                                          airports, and have taken training and check
              President's Column                          rides with the same individuals. To me that is
                                                          the really neat part about Ham Radio. You can
An old friend visited SPARC last Saturday.                meet a fellow Ham on the air or in person and
Ross Kauffman, W3ZKU, stopped by to donate                if you spend enough time you can find
some equipment to the Club. Ted, K3KSA,                   something other than radio in common.
Gerry, WB3SSZ and yours truly spent a few
hours reminiscing about old times and some                When was the last time you took the
more recent times.                                        opportunity to ask a Ham, either in the air or in
                                                          person, about their profession or interests
Ross is doing well and looks fit and trim. For            outside radio. You might be surprised what you
those of you who lost track Ross moved from               learn.
Lancaster to Philadelphia a few years ago. Ross
and his wife live in an apartment building in             73’
center city. Their first place was on the first
floor and while it was a large apartment it was           Harry, WA3FFK
not conducive to Ham radio. They are in the
process of moving to the 29th floor. Although it            Table of Contents
is a smaller apartment with less patio space the
propagation should be greatly improved.                     President’s Message                          Page 1
                                                            February Meeting Minutes                     Page 2
I am always amazed at some of the connections               Coming Events                                Page 2
you make when the stories start flying. I was               SPARC TS830S For Sale                        Page 3
surprised to hear that Ross had lugged a                    Editor’s Notes                               Page 3
generator to the top of Round Top to operate a              Six Meter DX Report                          Page 4
contest years ago. I was born and raised, and in            Intricacies of a Crowded Spectrum            Page 4
fact still live at the base of Round Top, now               ARES/RACES Information                       Page 5
State Game Land, near Middletown. Ted and                   SPARC Officers, Nets, Etc.                   Page 5
Ross have numerous friends and acquaintances                Tech Class Exam Diagrams T7                  Page 6
but discovered that they had other connections              Nearly QSO on 24GHz @ 461km                  Page 7
that they hadn't realized existed.

I had never known that Ross was a private pilot
and that we had probably crossed air routes at
some point in our lives. We have flown similar

     MINUTES OF THE FEBRUARY 2012                        •   Harry noted that the BOD wants to schedule
           MEETING OF THE                                    license classes this spring and is looking for
       SOUTHERN PENNSYLVANIA                                 volunteer instructors. He wants to hold
     AMATEUR RADIO CLUB (SPARC)                              sessions for new hams and for upgrades to
                                                             General. Some scout troops also expressed
    Held Tuesday, February 28, 2012 at 7 PM at               interest.
     the Rapho Township Municipal Building               •   The Tuesday digital net has moved to 7:30
                                                             PM, an hour earlier than its previous time.
                                                         •   Ross Kauffman is donating some equipment
The following members and guests were present:
                                                             to SPARC. He is moving into a smaller
 Dave Sarraf, N3NDJ                                          apartment and needs to downsize.
                                                         •   A work day at the site is needed to take care
 Lenny Borkon, W3LRB
 Harry Bauder, WA3FFK                                        of several antenna problems. Candidates
 Mike Warner, N3XPD                                          include April 14th, April 21st or April 28th, all
 Paul Herr, KD8WY                                            starting at 9:00 AM.
                                                         •   The digital linking system is expanding. Phil
 Ron Angle, KB3WTZ
 Kevin Lampo, K3LLC                                          Theis wants a node at his QTH. He will join
 Conrad Nasatka, WB3DQD                                      at the closest site, Cornwall, and may re-aim
 Gerry Wagner, KB3SSZ                                        after SPARC installs a 120° sector antenna.
 Ted Freedman, K3KSA                                         Two members residing at the Masonic
 George Gadbois, W3FEY                                       Village in Elizabethtown also want to
 Gerald Wilson, KB3GNB                                       participate. Dave Sarraf to investigate the
The meeting was called to order at 7:00 PM by                path and coordinate with Gary Blacksmith.
                                                         •   Ron Angle was voted in as a new member.
Harry Bauder.
                                                             His initial interest in ham radio was through
The meeting began with a technical session on a              radio controlled airplanes.
spectrum usage conflict between LightSquared
and the GPS system by Kevin Lampo. Kevin                 Respectfully submitted,
explained the history of the conflict and the            Dave Sarraf, N3NDJ
technical issues, and discussed recent decisions         SPARC Secretary
by the FCC and others.

The technical session was followed by a short            Coming Events
business meeting.
                                                         SPARC programs for 2011
General Topics
                                                         Tuesday, March 27, 2012.
•    Dave read and the prior month's membership          Dave Sarraf, N3NDJ, will speak on antennas
     meeting minutes. On a motion by Gerry
                                                         from “DC to daylight”. These are homebrew
     Wagner and a second by Paul Herr the
                                                         creations by Dave.
     minutes were approved as presented.
•    Mike Warner presented the treasurer’s report.
     On a motion by Ted and a second by Paul             Programs are needed for April and later.
     Herr the report was approved pending review
     by the audit committee. Harry noted that no         On April 12th, 2012, Skywarn Spotter
     problems were found with last year’s books          Training will be conducted by National
     on a review by two members.                         Weather Service-State College. This training is
                                                         sponsored by Lancaster County Emergency

Management Agency, and will be held at the             easily get on the VHF/UHF and microwave
Lancaster County Public Safety Training                bands with this fine radio. This one of the last
Center from 6:30pm-8:00pm.                             radios with tube finals.

Pre-registration is required by contacting Dave        Contact Harry Bauder, WA3FFK, for more
Boucher at dboucher@lancema.us .                       information.

June 9-10 2012 June VHF QSO Party                      Editor’s Notes
June 23-24 Field Day Paul Miller, N3APD, is            Field Day comes the last full weekend in June
the SPARC Field Day chairman.                          every year. This year the dates are 23-24 June.
                                                       Paul Miller, N3APD, is the SPARC Field Day
Wednesday, July 4, 2012, 11:00PM EDT                   chairman and needs your support. Field Day is
Aphelion, the Earth’s greatest distance from the       our big operating event of the year and includes
Sun and the approximate peak of the Summer             lots of camaraderie as well as operating. Come
Es season. Six meter DXpeditions are best              out and join the fun.
when planned to include this date. Expect good
Es conditions from about six weeks before to           The new FCC rules on the 60 meter band are
six weeks after aphelion.                              now in effect. Unlike other Amateur bands,
                                                       60m is channelized for USB operation. The
For a more detailed explanation, see “Sporadic         new rules permit very limited CW and digital
E, The Pieces Fall into Place” on page 6 of            operations. See the article by Dan Henderson,
March 2009 QRZ News.                                   N1ND, “New Privileges on 60 Meters” on page
                                                       74 of April, 2012 QST for in depth rules and
                                                       operating suggestions.
SPARC TS830S For Sale
                                                       Note especially that the new rules change the
                                                       frequency allocation for channel 3 from
                                                       5.368MHz to 5.3585MHz. For those who own
                                                       a Yaesu FT-857D or FT-897D, the 60m
                                                       channels are preprogrammed at the factory.
                                                       Per Tim Factor, KT7F of Yaesu Amateur Radio
                                                       Technical Support, the 60m channels are
                                                       programmed in firmware and can not be
                                                       changed in the field. At this time, Yaesu has
                                                       no solution for this problem. If you have one
                                                       of these radios, be very sure that you DO NOT
                                                       transmit on channel 3.

                                                       If you are interested in getting on 60m, Phil
This is SN 1081000 TS830S now on display in            Theis, K3TUF, is fully operational and can
the operating building at the SPARC site. You          listen for your signals.
can inspect the transceiver during one of the
odd Tuesday operating sessions or by                   73, George,
appointment. The transceiver is in excellent           W3FEY
condition and surplus to our club needs. There
is a built in transverter interface so you can
Six Meter DX Report                                  The intricacies of a crowded
                                                         spectrum: A Look at
15 March 2012                                        GPS, LightSquared and the
  Six meters has been very slow in this                          FCC
area. Around the world; however, there              By Kevin Lampo, K3LLC
have been some spectacular contacts.
The TEP season is beginning and stations            Ed Note: This is a brief summation of the
in the Caribbean and occasionally the               excellent presentation on the topic by Kevin
southern areas of the gulf states have              Lampo at the February SPARC meeting.
been working into South America; stations
in Africa have been working into Southern           LightSquared and the GPS industry have spent
Europe, and stations in Australia, New              the last 18 years building a battle full of
Zealand and Oceania have been working               important and critical issues surrounding FCC
into Japan. These contacts occur on a               spectrum allocations and utilization. This
regular, if not daily basis, in the afternoon       article from the New York Times sums up the
and early evenings local time.                      issues, the players, and the root causes of this
                                                    conflict. http://tinyurl.com/NYT-LSGPS
  On March 11th at 23:36UTC ZL1RS
(New Zealand) worked EA8BPX (Canary                  The technical details at the heart of the issue is
Islands) via what we think was F2,                  best described in a report produced by JAVAD,
although on one is quite sure; on                   a component manufacturer, who designs notch
March 9th K1TOL in Maine worked KL7KY               filters for receivers.
(Alaska) at 03:45 UTC on auroral E. The E           http://tinyurl.com/JAVAD-LSGPS
and F2(?) were undoubtedly related to the
solar activity of last week.                        The final link is the FCC's public comment
                                                    page regarding the recent denial of
    For operators interested in seeing a            LightSquared's permission to operate.
visual representation of the 6 meter activity       http://tinyurl.com/FCCPub-LSGPS
on a daily basis, I recommend the
ON4KST Region II chat page. See                     The final outcome of this issue has far reaching
http://www.on4kst.com/index.php. Click              implications on how finite spectrum is being
on the menu box in the upper left corner            used, underutilized, or quarantined because of
and click on DX history map. Although               out of band reception for more than a decade,
there are occasional bogus entries caused           and slow and stagnant allocation procedures
by stations using the DX clusters for               that do not keep pace with
station to station communicating rather             technology.
than spotting contacts, the maps provide
an excellent reference of daily propagation
paths on six meters.

   One other note-Senegal is now legal on
6 meters.

  73 Chris W3CMP

ARES/RACES                                                        Club Officers
                                                                  President Harry Bauder – WA3FFK
                                                                  Vice-President: George Gadbois – W3FEY
                                                                  Secretary - Dave Sarraf. - N3NDJ
                                                                  Treasurer - Mike Warner – N3XPD
                                                                  Repeater Trustee - Dave Payne - N3LOM

                                                                  Nearby Nets of Local Interest
  As part of the SPARC commitment to emergency
                                                                  York County Sponsored Nets:
communications, the SPARC repeater system is
maintained as available for linking with other area               Tuesday Digital Net
repeaters.                                                         Tuesday, 8 PM on the York 146.97 Repeater --
  Lancaster County RACES VHF Net is held on the first             This is busy digital data training net for
Tuesday of the month at 2030 hours local time on the              beginners and advanced users. The primary
145.310 MHz repeater in Rawlinsville.                             mode used is MT63-2k. Call in by voice or
   The Lancaster County primary ARES/RACES repeater               digital mode.
is on 145.310 MHz with minus offset and 118.8 PL.
                                                                  Friday Digital Net
 Combined York County Amateur and ARES/RACES                      Friday 8 PM on the 146.610 (PL:131.8 Hz)
NET convenes at 8:30 PM (2030) Mondays on 146.97.
                                                                  EARS repeater on Ephrata Mountain.
   Pennsylvania RACES HF Nets are held at 3993.5 kHz
LSB on all Sundays except holidays.                               This is an excellent Digital net called by Bob,
   The statewide net is on the first Sunday of the month at       AB3GF. Check in is by digital or voice.
0800 hours local time.
   The Central Area (including Lancaster County) net is
at 08:30 local time.                                              The standard digital mode is MT63-2K, other
                                                                  modes by request. It is an informal, well run
 EPA NBEMS Net, Tuesday, 7:30pm local                             net with plenty of Digital transmissions along
EST,                                                              with discussion by voice.
  3.5920mhz Mode: Olivia 8/500 1khz,
  Net Mgr: WA3WSJ@arrl.net                                        HF 75 METER NET --- Cancelled for the
                                                                  meets Tuesday at 9:00 PM (2100)
SPARC Nets                                                        meeting at 3830 or if busy around 3820
  SPARC holds nets every Tuesday at 2100 local time
                                                                  NCS: Bob Riese, K3DJC; backup NCS: Bob
on 145.230 MHz minus offset and a PL of 118.8. The                Gundlach, N3NBT
449.975MHz repeater is linked to the 2m repeater for the
net.                                                              KEYSTONE MARCONI NET
  The previously announced digital net has been                   Monday Night – 1830-2030 EST (before the
cancelled. SPARC repeaters are available for digital              Keystone VHF Net)
testing and emergency traffic.                                    Wednesday Night – 1900-2100 EST (before the
                                                                  QCWA Net)
  SPARC has a digital station set up in the operating
building for those wanting to check in to the digital nets.
                                                                  Thursday Night – 1900-2100 EST
Weather permitting, there is usually someone there to             Friday Night – 1900-2100 EST
help except on club meeting nights.                               Saturday Night – 1900-2100 EST
                                                                  Sunday Night – 1900-2100 EST

KMN is the Pennsylvania slow speed
                                                                The names of system blocks in Figure T7
Marconi Net which meets once a week
                                                                diagram are shown in the following image.
here to train all radio amateurs in
acquiring code proficiency. All are
The Net frequency will be 28.050 +/-
for QRM. Please go the ARRL website
and download form FSD-218. This
form has all the ARRL QN signals for
CW Net use. You should already have a
copy of the Q signals, which I had
previously sent to you via email.
If you have any questions before or after the
KMN, please E-mail and let me                                   There is only one question mandated for the
know. K3PXC@comcast.net                                         Technician Class diagram figure T7:
                                                                T7A04 - What circuit is pictured in Figure
PACKRAT MONDAY NIGHT NETS                                       T7, if block 1 is a frequency discriminator?
Visit the Mt Airy VHF Radio Club at:
http://packratvhf.com/airtimes.htm for the latest               True Answer: An FM receiver.
information on VHF/UHF nets.                                    ~~
                                                                Edwin Howard Armstrong (December 18,
                                                                1890 – January 31, 1954) was an American
QRZ News Publication                                            electrical engineer and inventor. Armstrong
QRZ News is published monthly approximately ten days            was the inventor of modern Frequency
before the monthly meeting. Please submit items for             Modulation (FM) radio. Edwin Howard
publication as early as possible. If a large amount of          Armstrong was born in New York City, New
editing is required, earlier submission is required.            York, in 1890. He studied at Columbia
We operate on an exchange basis with other non-                 University and later became a professor
commercial publications. Articles printed in QRZ News           there. He invented the regenerative circuit
may be reprinted in a not for profit publication provided       while he was an undergraduate and patented
proper credit is given                                          it in 1914
                                                                (used by U.S. Army Signal Corps in WW1),
QRZ News is archived at
                                                                the superheterodyne receiver in 1918,
Documents are in PDF format.                                    followed by the super-regenerative circuit in
                                                                     Armstrong is possibly best known for his
  Technician Class Exam Diagram                                 discovery of wide-band radio Frequency
                T7                                              Modulation. FM was born of a request by
            By James L. Ibaugh, AA3C                            David Sarnoff of RCA as a means to
  From the Element 2 Technician Class Q&A                       eliminate static in radio reception. In 1946
Pool, there are seven simple diagrams in the                    the FCC's decided to use Armstrong's FM
Technician's exam, of which three are                           system as the United States standard for
schematic and four are block diagrams. The                      NTSC television static and noise free sound.
Figures T1, T2 and T3 are schematic symbol                       Understanding FM Receivers - Doug DeMaw,
diagrams. Figures T4, T5, T6 and T7 are                                              W1FB
system block diagrams.
                                                           Frequency modulation can be regarded
                                                        as phase modulation where the carrier phase
                                                        modulation is the time integral of the FM
                                                        modulating signal. Radio communications
                                                        systems using frequency modulation with
                                                        sufficient bandwidth provides a very large
                                                        advantage in canceling naturally occurring
                                                        noise (static) and man made (machine)
                                                        electrical noise in the RF spectrum.
                                                            Please pass this newsletter or article on
                                                        to anyone that may want to take the
   The standard Amplitude Modulated                     Technician Class Amateur Radio Operator
signal (AM) example starts out with a 100               Examination.
watt RF unmodulated carrier (CW) that is
then modulated with 50 watt audio                        All articles about diagrams “T1 toT7” used
frequency power which yields a AM signal                in the “Technician Class Examination” can
that is 100% modulated. The AM process                  be found in various issues of our newsletter,
uses 150 watts total and only 33% of the                             SPARC's QRZ News.
total signal power carries audio.

   A 150 watt FM carrier wave changes
100% of the power in the frequency domain
in step with the audio signal. FM has three
times more communication efficiency than

              A “Nearly QSO” on 24 GHz over a 461 km Path using JT65c
                          By Rex Moncur VK7MO and David Smith VK3HZ

Tests between David VK3HZ and Rex VK7MO were undertaken on 24 February 2012 over a 421 km
path between John’s Hill lookout and Mt Barrow Tasmania over a non-line-of-sight path as shown in
Fig 1. The tests were undertaken at a time when the Hepburn tropo index (Fig 2) indicated that ducting
should be possible. While a QSO was not completed three full decodes were exchanged suggesting that
such a path is possible on 24 GHz. The path of propagation is in white and the pink lines show
domestic aircraft routes. The tests were undertaken with JT65c and also test tones on 1270 Hz. The
means of propagation is not entirely certain but it is likely to be due to high level tropospheric ducting
- the duct producing low propagation loss for a non-line of sight path and the high level duct (around
2000 metres) ensuring low absorption losses as a result of lower densities of water vapour and oxygen.
Comparisons were made with 10 GHz which gave signals around 50 dB greater.

Figure 1: Locations for Tests between John’s Hill lookout (VK3HZ) and Mt Barrow (VK7MO)

Figure 2: The Hepburn Tropo Index chart at 0000 on Friday 24 February coincides closely with the
time the tests were run and shows a good yellow patch between Mt Barrow and John’s Hill lookout,
which suggests there should be enhanced signals.
10 GHz Comparison

Figure 3: 10 GHz Signal to Noise ratio in 2.7 Hz bandwidth with single tone
Tests on 10 GHz showed a consistent tropo path with signals varying between +4 dB and -6 dB on the
WSJT scale. As WSJT tends to compress below -10 dB these signals are in fact much stronger and by
ear were estimated at 5/9 plus. Figure 3 shows the peak signal reached around 60 dB above the noise
in 2.7 Hz bandwidth, equivalent to around +30 dB on the WSJT scale. As WSJT can detect signals
down to around -30 dB by eye the 10 GHz signal was some 60 dB above the detectable limit. This
level is stronger than for previous 10 GHz tests over similar paths and suggests some tropo
enhancement. Given the good conditions forecast by Hepburn these tests were arranged on the basis of
the possibility of tropo-ducting at 24 GHz. However, despite 10 GHz showing signal levels some 60
dB above the detectable limit there was no evidence of consistent tropo on 24 GHz. In fact over a
period of almost 2 hours there was evidence of 24 GHz signals for only 11 minutes. The best signal
seen on JT65c on 24 GHz was -24 dB and by eye the peak would have perhaps reached -15 dB still
some 45 dB less than the peak seen on 10 GHz.
The fact that the 24 GHz signal rose from the noise for a short period and that there was no evidence of
the signal at all at other times did make us think that it could have been due to aircraft scatter.
However, the signal was essentially stable in frequency to within a few Hz for the 11 minutes that a
signal was detected and this is very unlikely based on our experience of aircraft scatter at 10 GHz. In
addition the path of propagation is not in line with any domestic aircraft paths and we would have been
both beaming too low for aircraft. Thus our conclusion is that the signal was most likely the result of
tropo-ducting which only rose above the noise for this short period of 11 minutes.
The best tropo-ducts have been measured to produce signal levels approaching line-of-sight
propagation. A calculation of the line-of-sight losses indicates that the peak signal levels on 10 GHz
were about 40 dB below line-of-sight so it is still possible that much better paths might be obtained.
Equipment Comparison
24 GHz
VK3HZ: Thales module and 38 cm dish (37 dBi) – estimated 1.5 watt TX and 1.5 dB sun noise on RX
VK7MO: DB6NT transverter, pre-amp and 3 watt PA to 47 cm (39 dBi) offset dish – estimated output
3 watts to feed and 4 dB sun noise on RX
10 GHz
VK3HZ: Qualcomm transverter, DEMI PA with 7 watts to the feed 60 cm (34 dBi) dish DB6NT pre-
VK7MO: DB6NT transverter, pre-amp and 10 watt PA to 64 cm (34 dBi) offset dish – 7 watts to feed
and 3 dB sun noise
The basic free space propagation loss is 20 log10(24048/10368) or 7.3 dB greater at 24 GHz.
RX system noise will be similar on all systems as it is basically limited by ground noise when beaming
at the horizon
TX power is up on 10 GHz by around 4 to 7 dB say 6 dB.
Antenna gain is up on 24 GHz by 8 dB
Thus system performance should be around -7 – 6 +8 dB or around 5 dB down on 24 GHz. As the peak
signals on 24 GHz were around 45 dB below those on 10 GHz this suggests that the additional
propagation losses (probably due to absorption on 24 GHz) were around 40 dB.

Height of Ducts

Figure 4: Radiosonde Data at the time of the tests from near Melbourne (the VK3HZ end of the Path)
as provided by the Bureau of Meteorology via the University of Wyoming.

Fig 4 shows temperature on the right hand side and it is seen there are two inversions. From the raw
data below the lower inversion is 2.5 degree between 333 metres and 704 metres which would be too
low to be useful from Mt Barrow location at 1300 metres. John’s Hill lookout at 408 metres would be
within this inversion and may be partly trapped. The raw data shows the higher inversion between
2298 and 2472 metres which is above Mt Barrow and possibly explains the enhanced signals on 10

94866 YMML Melbourne Airport Observations at 00Z 24 Feb 2012

    hPa     m      C      C      %    g/kg    deg   knot     K      K      K
 1007.0    119   23.8   14.8     57 10.61      65      5 296.4 327.3 298.2
 1000.0    175   22.2   13.2     57   9.62     45      9 295.4 323.3 297.1
  984.0    315   21.4   12.4     56   9.27      5     16 295.9 323.0 297.6
  982.0    333   21.5   12.0     55   9.06      0     17 296.2 322.7 297.8
  941.0    704   24.0    4.0     27   5.44    330     20 302.4 319.0 303.4
  935.0    759   23.9    3.1     26   5.14    325     21 302.8 318.6 303.7
  925.0    853   23.6    1.6     24   4.67    325     22 303.4 317.9 304.3

 921.0      891   23.4     1.4    24   4.62   323        22   303.6   317.9   304.4
 900.0     1090   21.9    -1.6    21   3.80   315        23   304.0   315.9   304.7
 850.0     1583   18.0    -9.0    15   2.29   300        20   305.0   312.4   305.4
 818.0     1907   15.5   -13.8    12   1.62   290        19   305.7   311.0   306.0
 781.0     2298   12.4   -19.6     9   1.04   294        16   306.4   310.0   306.6
 765.0     2472   13.4   -25.6     5   0.63   296        14   309.3   311.6   309.5
 734.0     2816   11.4   -26.2     5   0.62   300        11   310.9   313.1   311.0
 700.0     3211    9.2   -26.8     6   0.61   310        13   312.6   314.9   312.8
 696.0     3258    9.0   -23.0     8   0.87   310        13   313.0   316.1   313.1
 695.0     3270    9.0   -22.0     9   0.95   309        13   313.1   316.4   313.2
 647.0     3851    4.8   -23.6    11   0.89   260        14   314.8   317.9   314.9
 595.0     4531   -0.1   -25.4    13   0.82   255        17   316.7   319.7   316.9
 575.0     4809   -2.1   -26.1    14   0.80   258        19   317.5   320.4   317.6
 521.0     5588   -5.3   -36.3     7   0.33   266        25   322.7   324.0   322.8

Figure 5: Raw Radiosonde Data – inversions highlighted in green
Absorption Losses
We can get some idea of the absorption losses using the ITU methods (Rec. ITU-R P.453-9, P.836-4
P.676-8 provided by VK3UM). In the table below we have used the temperature and relative
humidities from Figure 5 for heights of 400 metres representing the height of VK3HZ and 1300 metres
which is the height of VK7MO.

Height            Pressure       Temp (deg     RH (%)             Loss/Km (dB)        Total
(metres)          hpa            C)                                                   Absorption
                                                                                      Loss (dB)
400            960             22              40                 0.18                76
1300           840             21              18                 0.08                36
Table 1: Absorption losses at 24 GHz
Height         Pressure        Temp (deg       RH (%)             Loss/Km (dB)        Total
(metres)       hpa             C)                                                     Absorption
                                                                                      Loss (dB)
400            960             22              40                 0.013               5.8
1300           840             21              18                 0.008               3.4
Table 2: Absorption losses at 10 GHz

The absorption losses have a small impact of 10 GHz which suggests that the 10 GHz signals are in
fact around 35 dB less than for line-of-sight. The additional absorption loss at 24 GHz would be
around 70 dB if the path was in a duct at 400 metres and around 32 dB if the path was fully around
1300 meters. The measured difference of 40 dB is thus plausible as the path would be somewhere
between the two heights.

Results of Tests

Figure 6: Results Received by VK7MO
As shown in Figure 6 VK7MO received two good decodes at -26 (0019) and -27 dB (0021) with DF
plus 8 and plus 5 Hz. There is evidence of the signal at 0015 Hz with 3 Hz DF and 0017 with 8 Hz DF
when David was transmitting a 1270 Hz single tone. While these signals are typical of aircraft scatter
there is no evidence of significant Doppler on the DF and in fact David VK3HZ’s signal always
decodes at 8 Hz DF on 10 GHz on tropo so this made us think it was unlikely to be aircraft. Also as
shown on Figure 1 no domestic aircraft cross the route and in any case as we were looking for tropo we
were beaming too low for domestic aircraft.
At VK3HZ’s end the signals decoded were as shown in figure 7.

Figure 7: Shows decodes obtained from files recorded by VK3HZ

During the actual test VK3HZ decoded only the file at 0026 as he had not set the grid square in which
VK7MO was operating at time 0018 and the rate in needed to be adjusted to one to decode the file at
0022. Thus potentially VK3HZ could have achieved 3 decodes.
There is evidence of the signal from 0015 as RXEd by VK7MO to 0026 as RXed by VK3HZ or for a
total on 11 minutes. The DF is essentially stable over this period which tends to rule out aircraft
It is also noted that the JT65c signals are well constrained to within a few Hz with WSJT reporting
widths of 3 to 6 Hz. From our tests on 10 GHz we have seen spreading on tropo-scatter of 10 to 20 Hz
with ducting producing very narrow signals – thus the narrow signals on 24 GHz are consistent with

It seems plausible that the signals were via tropo-ducting and that the major difference between 10
GHz and 24 GHz can be explained by the additional absorption losses at 24 GHz.
Calculations of absorption Loss suggest that the ducting was at high level around 2000 metres.
The ducting signals are stable and constrained within one JT65c bin and thus that JT65c is useful for
tropo-ducting at 24 GHz.
It seems that for planning purposes it will be necessary to use high ducts to avoid excessive absorption
and that it will be preferable also to have elevated TX and RX locations to reduce absorption losses.
While a QSO was not completed in this case (due mainly to stuff-ups) there is evidence that such a
path is possible given that this was our first attempt.


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