Computer Control for Mobile Ham Radio Operation by broverya77


									Computer Control for Mobile Ham Radio Operation
A simple interconnect, some software and an inexpensive palmtop make mobile remote
control easy!

Arthur I. Zygielbaum, WA6SAL

   HF mobile operation is fun! Given a long commute in heavy traffic, nothing seems to make the time go faster than a good QSO.
Among my memorable contacts, I was explaining the difficulties of Los Angeles rush-hour traffic to a ham in middle Tennessee. He
asked me to stand by while he went to a window. The town store was about to close and he wanted to enjoy their “rush-minute”!

   Modern vehicles challenge the HF mobileer. You worry about electrical noise, damaging the vehicle’s computer module and
wonder how you’re going to mount a radio in a cramped dash with a center console and lots of gadgets. My 1991 Toyota Land
Cruiser posed such a challenge. This large 4-wheel-drive vehicle ought to have much room for radio gear. It doesn’t. The dash is
sculpted and cramped, and has a central console that consumes all available under-dash space.

     I had used my faithful ICOM IC-725 in another car. There was no way that it was going to fit into the front of the Land Cruiser!
(When I started this project, the Kenwood TS-50 was not available. But even that small radio would have been difficult to mount.)
Could my ’725 be remotely mounted? Remoting the front panel would require 50-plus wires and considerable dash space. It was
difficult, probably doable, but not esthetically acceptable.
    Fortunately, technology came to the rescue. The IC-725 has the digital interface common to many of the ICOM HF and
VHF/UHF radios. Any computer with an RS-232 port can—with some level shifting and some software—control the radio. [1]
Eureka! I could use a small computer—a palmtop—to remotely control the radio. I could, in fact, build a digital front panel that would
allow features that I have always wanted in a radio. The result is a radio control program that I use on my palmtop in the car and on
a desktop computer in my ham shack. Here’s how you can have the digital and analog electronic interfaces, the computer software
and the virtual front panel that evolved.

Which Computer?
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   Because I program for PCs, this software is designed for use with PCs and compatibles. I wanted a program that would run on
any PC compatible, from a lowly 8086 on up—desktop, laptop and palmtop.

   For use in my car, I chose a PC-compatible palmtop—the Hewlett-Packard HP 95LX with 512 kB of RAM. It is functionally
identical to PCs (with some exceptions noted later), relatively inexpensive and has a serial port. Used HP 95s are available for about
$150. [2] Using an HP 95 has the added benefit that any software I develop for it will also run any other PC compatible.

The Digital Interface
    The ICOM Communications Interface V (CI-V) provides an RS-232−based network for the interconnection of computers and
ICOM radios. [3] Electrically, the interface is compatible with RS-232-C (typically at 1200 baud), works at TTL voltage levels, and
uses only two interconnecting wires. (The cable between the computer and the radio must be continuously shielded to minimize
noise. Most high-quality RS-232 cables are suitable.) A level converter (such as an ICOM CT-17) is required between the interface
and the RS-232 levels used at computer serial ports. I built my own level converter based on the MAX232 level-conversion IC.
Similar interfaces have appeared as QST construction projects and others are advertised in QST. [4]
    Logically, the interface is carrier sense multiple access with collision detection (CSMA/CD). As with packet radio or an Ethernet
connection, any device in the system can access the interface at any time. If a collision occurs, communication is retried based on a
timing protocol. Each device on the interface has a unique, single-byte address. Information is contained in packets consisting of a
preamble, target address, source address, control code, data and end-of-message marker. (See the references cited earlier for
more information.)

The Analog Interface
    Audio signals, along with computer remote-control signals, must be routed from the remote radio to the operating position. An
on/off switch is needed, too. I use a small box to contain an on/off switch to control the battery connection to the radio, a volume
control pad to adjust the amount of audio feeding the speaker, and a mike jack that connects the mike audio, mike frequency
step-up/down controls and PTT lines to the radio. Figure 1 shows the interconnections involved. A four-wire shielded cable between
the ’725’s front-panel mike jack and the control box handles the interconnection. The small box mounts under the dash. To avoid
having to replace batteries, the box also incorporates a power supply for the palmtop computer.

Figure 1—Block diagram showing the interconnections required for my mobile setup.

The Software Interface
    The software (see Note 1) used to implement the remote control is written for DOS and is based on an assembly language
serial-communications package that I wrote several years ago. Because of documented hardware bugs in the HP 95LX, several
modifications were required to accommodate the HP 95’s serial ports. The radio control application itself is written in Turbo Pascal
and makes use of pop-up windows for several functions.

Build a Front Panel
    With a computer, you can design and build your own front panel—all in software! This was a fantastic opportunity to implement
the features I always wanted in my radio. The IC-725 and IC-735 offer relatively limited control via the digital interface. Software can
control frequency, mode and the frequency memories. I chose to control frequency and mode; I could build all the memories I
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wanted into the software.

   To maintain consistency, I felt it necessary to synchronize the radio’s front panel and the front panel presented on the computer
screen. Frequency and mode changes made at the front panel of the radio are tracked on the computer screen (and vice versa). In
case of conflict, the computer wins!
    Several what-I-always-wanted features are included. The program is case-insensitive if letter keys are pressed, and all
commands are set up for one or two key presses. Frequently used keys are at the edge of the HP 95LX keyboard and in places that
can easily be found by touch. This is important for mobile operation—you must keep your eyes on the road! I can scan, hear a
station and tune it in without looking at the keyboard.

    Figure 2 shows the main screen. The frequency, band and mode fields are self-explanatory. The field labeled Scanning will be
discussed later. The center field shows the current time and date. The number at the left is the lower scan-limit frequency; that on
the right is the upper scan-limit frequency. Just above the date and time is a graphical indication of the current frequency with
respect to the scan limits.

Figure 2—The main screen. The displays shown in Figures 2 through 6 are screen captures made while using a desktop
PC-compatible computer. The HP 95LX display is identical except for a different aspect ratio.

Band Stacking
    Depending on the radio used, 10 or 12 bands are recognized. Nine HF amateur bands (160, 80/75, 40, 30, 20, 17, 15, 12 and
10) are available for most radios. The IC-706 adds 6 and 2 meters. One additional “open” band is provided; it can be set anywhere
                                                                                                            →           ←
within the radio’s tuning range. The program allows shifting cyclically from one band to the next by right (→) or left (←) arrow key
presses. Frequency, mode and scanning limits are stored for each band. If you manually input a frequency from within one of the
amateur bands, the program automatically chooses the correct band: an amateur band or the open band. The program will not leave
the open band except by shifting cyclically up to the 160 meter band or down to the 10 or 2 meter band.

Changing Frequency
    There are several ways to change frequency: manually, by typing in a frequency, or by using the up (↑) and down () arrow keys
to start, speed up or slow down frequency scanning (described later). Frequency changes in 50-Hz steps are available by pressing
the plus (+) or minus (–) key. If you want to change frequency by 1 to 9 kHz, press the corresponding number keys from 1 to 9; for
10, press 0, followed by the + or – key. You also have the ability to quickly input offsets of from 1 to 50 kHz by typing in the offset.

    Like most mobileers, I spend a lot of time tuning the band to find stations looking for contacts and trying to find exotic DX
stations. Scanning is an important part of the control program.

    There are two main scanning modes: limited and unlimited. Limited scans are constrained by end-point frequencies. The
program steps the frequency up or down at one of three selectable rates. When it hits an end point, it resets the frequency to the
opposing end point and continues stepping. Unlimited scans are just that—they just keep on going. Pressing the DEL key toggles
the limited or unlimited scan feature.
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   Scanning is initiated by pressing one of several keys. If the ↑ or key is pressed, the program begins scanning up or down,
respectively. It will start at the slowest rate, 50 Hz per step. If the same key is pressed a second time, the program increases the
step size to 1 kHz. Similarly, if the same key is pressed a third time, the program increases the size to the largest step size, 10 kHz.
If at any time the opposite key is pressed (, if ↑ were the original key, for example), the program decreases the step size. Continued
pressing of the opposite key eventually stops, and then reverses, the scan.
   When scanning SSB signals, it is best to tune down the frequency slope—from highest pitch to lowest. That gives you the most
time to listen and interpret what is being said. Pressing the equals (=) key causes the program to automatically initiate 1-kHz-rate
scanning downward if LSB is selected, or upward if USB is selected. The AM, CW, and FM modes are also scanned if the = key is
pressed, but arbitrarily upward at the 1-kHz rate.

   Scanning can be stopped by using the opposite arrow key as described earlier, by pressing the + or – key to stop the scan
immediately, or by pressing the period (.) key to stop the scan at the frequency at which the scan was started.
    The forward slash (/) key is used to tune in a station while scanning. Pressing the / key causes the scan direction to reverse and
the scan rate to drop to the next-lower step size. Repeated presses continue the reversals, but the step size is reduced only to the
minimum step size, 50 Hz. When a station is approximately tuned in, scanning is stopped by pressing the + or – key. As described
earlier, the + or – key can then be used to step up or down 50 Hz for precise tuning.
    Sometimes it is convenient to scan a small range of frequencies. For example, if you are tuning and catch just the end of a
transmission, it is good to scan about that frequency so that when the station transmits again, you can tune it in. Pressing the
asterisk (*) key causes the program to orbit, that is to scan within limits of ±5 kHz of the starting frequency.

    There are six selectable scan limits for each band. You can customize two of these sets. The remaining four are preset to
correspond to the voice privileges of the various Amateur Radio licenses. You can select either of the custom sets, or the limits for
Novice/Technician, General, Advanced, or Amateur Extra license holders.
    Figure 3 shows the computer screen while scanning. The upper-right field shows that the scanning direction is up, that the scan
step size is medium (1 kHz) and that the scan limits are set to the Custom 1 limits. The middle field shows that the band scan is
active. A graphic arrow shows the direction of scan. The characters used for the arrow’s horizontal line change in response to the
scan step size, so you can quickly recognize the scanning speed.

Figure 3—Main screen while scanning

   Orbiting or scanning ±5 kHz looks similar. During orbit scan, the screen appears as in Figure 4. Figure 5 shows the screen
while selecting scan limits.

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Figure 4—Main screen while orbit scanning

Figure 5—Selecting the scan limits.

  In the current software version, there are 10 memories. Each memory position stores frequency, mode and band. Recalling a
memory resets the “front panel” to correspond to what was stored.

Mode Selection
   Mode selection is especially simple. Press A for AM, F for FM, W for CW, L for LSB, and U for USB.

Tuning Function
    It is important to be able to transmit a steady carrier or signal to test and adjust an antenna. Pressing the T key puts the program
into a tune function. While in tune, keyboard entries can set the transmit mode, set the transmitter frequency to the center of the
current band (the center of the frequencies allowed for the current mode) or to the center of the current scan limits. For example, I
usually set the mode to AM (for a half-maximum-power carrier) at the center of the scan limits. When tuning is complete, pressing
ESC exits the tune function and returns the radio to the frequency and mode previously in use.

    Most hams like to keep logs of MF/HF contacts. It seemed logical to implement a logging function in the control program. Since
the program knows the frequency, time and mode, you simply add the station call sign and other pertinent information. The log
function includes simple editing and text search. A sample entry is shown in Figure 6. These log entries are kept in a
comma-delimited format that allows the file to be used by most database management programs to print a log or generate QSL card

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Figure 6—Logging screen

Prefix/Country Look-Up
    As a convenience, I’ve included the ability to find the name of a country based on a call-sign prefix and find a prefix based on the
name of a country. While scanning the band, it is useful to identify a country when you’ve heard a prefix. Similarly, if you are looking
for a particular country, it is nice to know which prefix to look for.

My Experience
  The cockpit installation is shown in the title photo. Super Velcro holds the HP 95 to the center console. The remote control box is
mounted out of sight under the dash and to the left of the console and the radio is in the rear of the vehicle.

    I’ve used this HP 95LX control program for about three years, changing and upgrading it as needed. [5] Several “design
features” were tried and rejected. It does take a little time to get comfortable using the push-button interface versus a radio’s tuning
knob, but with practice, it becomes second nature. It’s amazing to realize that sometimes I will start scanning, then discover that I’ve
unconsciously tuned in a station!
    With the ICOM IC-706 and similar remotable radios, it is possible to move the front panel to the front of the car, keeping the
radio in the trunk. I would not, however, want to give up the convenience of the scanning, logging and rapid frequency change that is
available using the computer.

    I use the software to control my IC-735 at the home station. Depending on the configuration of the moment, the radio is
interfaced either to a 75-MHz 80486, or 166-MHz Pentium computer. I find the software controls are very convenient, compared to
using the radio’s front-panel controls.

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Control box wiring. A voltage regulator is included to deliver 8 V to the computer.

Future Enhancements
  Since this program was first written, it has been through many versions. Future enhancements will increase the number of
memories, add a contest log (to avoid duplicate contacts), expand the interface to take advantage of the features in later ICOM
models and extend the software interface to encompass radios from other manufacturers.

      A Windows spin-off and VHF/UHF remote control capabilities are also under consideration.

1The program runs under DOS 3.2 or higher, and in a DOS window under Windows 3.1x and Windows 95. The software is available

on a 3.5-inch diskette from the author for $25. At the purchaser’s option, the program can be copied to a PCMCIA RAM card
supplied by the purchaser. The price includes a full year of updates. Please contact the author at 4910 Hampton Rd, La Canada, CA
91011, or via e-mail at, or via fax at 818-952-2140. Although the software operates the same functions on any
CI-V equipped ICOM, future versions of the software will take advantage of enhanced functions in later ICOM radios. The program
will also be expanded to encompass transceivers from other manufacturers.
2The HP 95 was superseded by the HP 100LX, which has itself been superseded by the HP 200LX. Although discontinued, used

HP95LXs are frequently available from Global Connections, 170 S Jackson St, Janesville, WI 53545, tel 800-709-9494,
608-752-1537; fax 608-752-9548. Price (subject to change) is about $150 for a 512-kB memory version. Other palmtop models are
also available from this source.
  is described in papers available from ICOM, in the manual for the CT-17 level converter, in various files posted on BBSs and
Compu-Serve, and by Wallace R. Blackburn, AA8DX, in “Everything You Always Wanted to Know About Hardware for
Computer-Controlling Modern Radios,” QST, Feb 1993, pp 37-41.
4See these articles for some ideas: Mark Shelhamer, WA3YNO, “Another Simple Interface for Transceivers with RS-232-C Ports,”

Hints and Kinks, QST, Jan 1994, pp 78-79; Gary Kalata, KC4ES, “An Inexpensive Computer/Radio Interface,” QST, Sep 1991, pp
24-25. See also Feedback, QST, Dec 1991, p 46, and QST, Mar 1992, p 86; Danny Stone, WB4ETY, “An RS-232-C Serial Interface
for the Yaesu FT-747GX/Heath SB-1400 Transceiver,” Hints and Kinks, QST, Jan 1992, p 91; Nigel Thompson, KG7SG, “A
Low-Cost PC Interface for ICOM Radios,” QST, Jul 1992, pp 37-38; and the 1997 ARRL Handbook, pp 22.46 to 22.48.—Ed.
5For another story on the HP 95LX, see Phillip Nichols, KC8DQF, “Portable Packets,” QST, Mar 1997, p 52. The sidebar identifies
a palmtop software site at—Ed.

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    Arthur I. Zygielbaum is an electronics engineer by training. He received a bachelor’s degree in physics from UCLA in 1968, and
a masters in electrical engineering from USC in 1975. During his 28 years at NASA’s Jet Propulsion Laboratory, Art developed
computer hardware and software supporting space science experiments and spacecraft navigation. He headed JPL’s Science
Information Systems Office, was Deputy Manager of the Information Systems Division, and spent several years working on NASA
teams developing recommendations for software standards and methodologies for the agency. Art serves on the National Research
Council’s National Weather Service Modernization Committee. During the past few years he has taken on special assignments in
the JPL Director’s Office, helping the Laboratory re-engineer its administrative structures. Currently he is co-principal investigator on
a research effort finding better ways to apply NASA’s vast data holdings to education.
    Art has been active in Amateur Radio for 36 years (since he was 14). He holds an Amateur Extra license. His wife, Chris, holds
the call sign N6WEI, and son David is KD6SAD. Daughter Debby may one day get a license! You can contact Art at 4910 Hampton
Rd, La Canada, CA 91011, e-mail Photos by the author.

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