Chris Kantarjiev
Previous call: KG6VYD

Find me via APRS

Random commentary and tracks through my (short) amateur radio career.

Long, long ago I first started studying for my license in 1971, when I was in eighth grade. I learned Morse from a book that taught it via picture mnemonics - R is for Racer, with a drawing of a race car, with the wheels being dit and the body a dah, for .-. and so on. It seemed to work, at least to 5 WPM. I studied the theory from the question pool, and understood most of it.

I never took the test. Mostly it came down to not having any money to spare for the hobby, nor the space to do my own construction. I don't really remember being too disappointed about it. The Novice bands didn't seem that interesting - my interest was in short-distance voice ("phone"), not DX code contacts.

Getting my ticket In the mid-90s, I started rock climbing and spending a lot of time outdoors. It wasn't too long before I started having adventures beyond the limits of cell coverage. When we bought a cabin in southern Yosemite, these became even more frequent.

At one point, we were up near Clover Meadow, an hour out of town, and got flagged down by a couple of fellows. They were looking for a way to get to a phone, or radio, or help. They had locked their keys in their vehicle. One of their party had drowned in the San Joaquin river.

The Clover Meadow station wasn't open yet, so we couldn't get at the radiotelephone there. We barreled down the Beasore Meadows road, stopping at each likely place, discovering no ability to communicate until we got to the Bass Lake fire station.

That was when I decided to get my ticket.

Things have changed a lot in 30 years. No code for a Technician license, most folks start by using 2m FM repeaters on handy-talkies. Just pass a 35 multiple choice question test that's half theory and half legality and you're a ham. A local club puts together "ham cram" sessions, where you spend a day learning the question pool, take the test, most likely pass it - and then figure out what you really need to know to operate. That's what I did.

Passed with flying colors, waited a week for my licence to show up in the FCC database, bought a used Yaesu VX-5R on ebay, and started figuring out how to live on the repeaters.

APRS One of the first things I discovered after getting my license was APRS, the Automatic Position Reporting System. If I'd known about APRS sooner, I'd have gotten licensed sooner - it combines a whole bunch of my history. I quickly bought a Pocket Tracker and built it. I hadn't built a kit for a long time, and this is a fairly dense one, so it got me up to speed right quick. I got it going the first time - that was very cool. And then I discovered that a 250mW transmitter doesn't have much of a chance in the SF Bay Area - the noise floor is too high and the terrain too varied to reliably hit the high digipeaters. And at our cabin in southern Yosemite, the digipeaters are too far apart. So I started learning a lot about the APRS digipeater infrastructure, and decided that I needed to build and deploy a couple in the areas where I want to play. You can find out how that's going here.

QRP Worse, I picked up The Joy of QRP in the library and am smitten. But I've promised myself that I need to get my APRS radios working before wandering off in that direction. Meanwhile, I started learning code...

Learning Morse Code Again So, of course, I find that I'm also interested in making DX contacts on HF! That required getting my General license. Which meant learning code...

I've split off my HF activities into a separate page because I think they will ultimately just confuse the narrative here...

Playing with radios I am an inveterate recycler, as you might have noticed from my other pages. At least, I like the idea of reuse, recycling and repurposing. In reality, it's a bit of a pain in the ass. But I tend to forget that.

So, to start myself off in amateur radio the right way, I bought up a bunch of used radios and am trying to make them useful again.

Western Radio I want to set up a couple of APRS digipeaters as well as a dedicated mobile unit in our FJ40. To that end, I bought some Western Radio crystal controlled commercial radios (WR-154, WR-154B, WR-155) from Eric Meth ve3ei got some new crystals from West Crystal and am working on tuning them up.

These radios were built in Japan by Unimetrics in the 70s. Western Radio was apparently a cross-border US/Canadian company - and if the radios were popular, not many of them made it into the ham community. That's too bad, because they seem pretty nice. I've scrounged some schematics and information: WR-154 schematic and WR-155 schematic. The WR-154B seems to be a hybrid - the WR-155 transmit board plus the WR-154 final PA assembly. Some of these radios came with multi-crystal cards, some with CTCSS/PL cards, some with multi-channel CTCSS cards! There's also a UHF version, the WR-1454 and friends. These seem to be slightly popular in linking or packet operations in Canada, but none of the usual suspects like know anything about them.

With the help of David WA0AUQ and his FM radio tuneup guide I got a good start on making the transmitter bark. Ed KD8KZ loaned me his Bird 43 and lots of email advice. Both of them told me to build an RF probe, and Ed loaned me an old Heathkit one that he'd had sitting in a tub for years. That probe was really the trick, since it let me see the small effects that individual adjustments were having.

I had managed to get RF most of the way into the final when Ed came to visit. We spent a long evening getting the transmit side going - adding a capacitor here, squeezing a coil there. Then we switched to receive - I thought this would be easy, but it was much harder. The high-Q input filters were very difficult to tune, especially since I don't have any standardized way of inserting a low-level signal. We got it going, but by the time we ran out of energy, it really wasn't sensitive enough. It would decode packets sent from nearby, but nothing at a distance.

After a small break to regroup my senses, I returned. One of the things Ed and I had noticed while setting the input filters was that the LO seemed a bit off. I kludged a way to notice when it was really on 144.39, added a couple of caps, did some repeaking, and it seems to be a radio!

I did some fishing around with a frequency counter, got the LO dead on, and the sensitivity seems to be pretty good. Unfortunately, I had messed up the IF settings (discriminator) in the process. I never figured out a way to improvise a microvolt RF generator - even putting my 1/4W transmitter in a metal box, with the antenna output attenuated and into a dummy, puts out a fairly hefty signal at the receiver. So I searched ebay and bought myself a really nice Fluke 6060AN syntesized RF generator. It was a lot more than I wanted to spend, but has been very useful in setting up MT500s, and has a deviation meter in it as well (good for setting up TNCs). Once the initial pain wore off, I've been glad to have it on the bench.

After the WR-154 was working for a while, I did the WR-155. That was much easier, for some reason, except adding a cap at the final output coil, which was a pain. I guess I learned a lot the first time around. I never quite got it to the rated 25W, but 22W is enough (and I'm not sure that the Bird 43 is really accurate).

MT500 I bought a batch of Motorola MT500 "handy talkies" on ebay: these were popular in the 1970s (you've certainly seen them in cop shows of the era). One version ("3 range") was made such that it could be used in the 2m ham band, if you put in the right crystals and retuned. Nowadays, getting the crystals and the crystal elements they fit in is somewhat more difficult, but I'm making progress. There's a fellow in Florida who specializes in these radios and other Moto products of the era: Bob Hicks, KA4LMW, aka BocaBob. West Crystal will cut new crystals for the crystal elements in these units, and can provide new ones, too. (Note that you need a particular model of Rx element for frequencies below 150.8MHz, but any Tx element will work.) The radios I got are the 5W model, have better than 1uV sensitivity, draw about 11mA at idle and less than an amp while transmitting. I think these will make dandy remote digipeaters (I'm imagining a ammo can or Pelican case with a battery, MT500, simple PIC-based digipeater, solar cell and a J-pole) and are a pefectly reasonable car-mounted tracker (I've given up on the Pocket Tracker). Bob tuned one up for me and built a cable for a TinyTrak3 which gives me a model for the rest of them. I've tuned up the rest and added a data connector - they're much friendlier to work on than the WR radios.

There doesn't seem to be a lot of info on these on the web; apparently a really big site disappeared. There are some similarities with the Motorola HT220, which has a good web presence. I've collected some information about model numbers, crystal elements and tune-up procedures - beware, it's pretty chaotic (the web page, too!)

Kenwood TH-D7 After resisting for a year, I finally bought a TH-D7A(G). This is a nice (albeit somewhat clunky) packaging of 5W dual-band HT and TNC, including built-in APRS microcode. It is a tracker (but doesn't do Smart Beaconing), can decode APRS packets and show information about the last 40 stations heard from, and engage in sending/receiving APRS messages - all the while leaving the second band available for voice work.

I find it kind of clunky as an HT, especially compared to my Yaesu VX-5. But for doing APRS work, and especially debugging APRS digipeaters, it's very very useful and fairly well thought-out. The stock antenna is miserable; I put on an SMA-to-BNC adapter (one of the nice ones that KC2BHO Stephen makes) and a Maldol 209 ducky. For use in the car, an external antenna is necessary or it won't decode any packets. After some experiments with mag mount antennas, I mounted a trunk-lip NMO mount, and mounted a Diamond NR72BNMO. This is a great little 1/4 wave dual-band antenna, only about 14" high. It's wonderful if you have a decent ground plane.

If you don't have a good ground plane, or can't put this more or less in the middle of the ground plane, the pattern will be very directional. In that case, you're better off with a half-wave antenna, like the Diamond NF770HNMO (about 40" high) or the Maldol EX107B NMO (about 29" high). I've had really good luck with both.

Since I move between vehicles pretty regularly, it's nice to have a portable unit instead of the bigger brother TM-D700. I usually use it with an eTrex Legend mapping GPS. The D7 will emit NMEA sentences that cause the GPS to record waypoints for every station that is heard, so I can see them on the map. That's a very cool feature.

Since I move this around, I wanted to minimize the cable clutter. I ended up with combination cable from pFranc, the eCombo, which is designed to provide power to the GPS as well as a data connection between the GPS and a PC. It turns out that the DB9F also gets power (3.3V) on pin 1. I opened up the cigarette lighter plug (start by unscrewing the gold ring) and moved the red lead in the PC-end cable to have input voltage (just before it goes into the DC-DC chip; I found a convenient resistor lead to solder to). I then made an adapter with a DB9M on one end and suitable data and power connections on the other for the radio. Took about an hour.

                    etrex               DB9F 
                    -----               ----

 CLP                  O >------brown----> 2    (data from GPS)
-----                 I <------white----< 3    (data to GPS)
ground <----black---> - <------black----> 5    (signal & power ground ref.)
3V out >----red-----> +
12V out >---red-------------------------> 1    (supply power to pD32 cable)

             DB9M	Kobiconn        Kobiconn
			171-3325	171-3224
             ----       --------        ---------

              1 >------------------------> tip  (+12V)
              2 >--------> tip
              3 <--------< ring
              5 >--------> shaft >-------> shaft

Now I have a single power plug providing juice for both the radio and the GPS, and much less cable tangle. I really like having the split at the cigarette lighter. I'm a little concerned that the cable has 26 gauge wire. The open circuit voltage at my bench supply is 13.9v; by the time it reaches the radio, it's down to 13.2v. (Part of that is a protection diode in the converter; I could wire around that.) Turning the radio on reduces that to 13.0v, and transmitting at the H setting drops to 12.2v! This shows only 4.2 watts out (VHF) into a Bird 43 wattmeter (10C slug). I'm not sure how well the small cable will sustain this; so far, I haven't had problems with the cable getting warm during longer (1 min or so) transmits. But I did blow the 1A fuse in the CLP when transmitting, running the GPS and having both radio and GPS backlight on! I replaced it with a 3A, which is what I had in stock. The original fuse is an odd size (AGX?), so I trimmed the spring and used a 'normal' AGC fuse.

I made the adapter with about a 6" long tail. I don't know if that's ideal or not. I used right angle plugs, but I think if I did it again I might use a straight power plug - the right angle plug with the tail pointed straight down seems to interfere with the dust cover for the power port, and I'm a bit worried that it will damage it.

I also made something similar to use with a Garmin GPS18 (which takes 5V on a DB9), in order to leave them permanently mounted in a vehicle. One less thing to carry around!

                    DB9M                DB9F
                    ----                ----

 CLP                  2 >------brown----> 2    (data from GPS)
-----                 3 <------white----< 3    (data to GPS)
ground <----black---> 5 <------black----> 5    (signal & power ground ref.)
5V out >----red-----> 8
12V out >---red-------------------------> 1    (supply power to pD32 cable)

I used a damaged dual-voltage eCombo cable as the starting point for that one - Larry sent me one without the Garmin connector - and moved the various power leads to match what's listed above for the radio, and to put +5V on pin 8 of the DB9M that goes to the GPS unit (my own standard, since there isn't any standard for pushing power into a DB9!)

VHF Antennas I made a quarter wave with ground plane, based on an SO-239, some 12 gauge solid wire, and a PVC antenna support I saw somewhere but can't locate right now. It works OK - zero reflected power on 144.39MHz, and mostly invisible: cheap 1/4 wave

The support system is 3/4" PVC pipe; there's enough friction that I didn't feel the need to glue it. If it got windy here, I would glue it, cap the legs and fill with sand. I don't expect the paint to last very well, but it doesn't get a lot of contact, so it might do fine! It seems to receive and transmit the signals around the neighborhood very well (and I occasionally get a direct receive from several hundred miles away). This is currently used for K6DBG-1.

I also built a 'copper cactus' J-pole for K6DBG-2, based on several designs on the web:
I built mine out of 1/2" copper pipe, which seems sturdy enough, and considerably lighter than 3/4". Listed dimensions are all over the place; it's possible that my antenna is actually a bit short, though I when I tried lengthening it by raising the caps, the reflected power went up, not down. So maybe not. I soldered a threaded fitting to the bottom for mounting on another PVC support bracket. has very detailed construction details. has a great discussion about the theory of operation!

I used the calculator at to locate the feed point exactly for 144.39MHz, since it's for an APRS digipeater. I used an N chassis connector riveted and soldered to the stub. Be careful while doing this that you don't melt the insulator!

One of the things that isn't mentioned on most of these pages is the need for a choke on the feedline, to reduce image current on the ground shield. You can do this with a few 5" loops of the feedline, but I didn't really like doing that to RG-8. I used, instead, a couple of these clip-on ferrite beads, a few inches from the feed point. This dropped my reflected power from about 1W to 0.2W - quite a nice difference in SWR (final value about 1.15:1).

But I still wasn't getting a full 10W forward, which concerned me. So I pulled out the torch and started moving the feedpoint; first I freed it up, then I clamped it into place with vise-grips so I could move it easily. I had to move the feedpoint up about an inch from the theoretical location to get full forward power - which brought my reflected power to less than 0.05W (the needle on the Bird 43 moves, but just barely, with a 10W slug), bringing the final SWR to 1.07:1. When I make another one, I'll try some sort of adjustable feedpoint mechanism. There are lots out there; I don't really like any of the designs I've seen yet. But being able to tune without a torch seems like a big win!

It's also important to seal the connection - especially the backside of the connector. I painted mine with Liquid Electrical Tape, to minimize moisture entering the coax via that route. The connector side gets covered with coax-seal.

I got permission to up a digipeater in Fish Camp (FSHCMP) and it is considerably higher than everything around it. In this situation, the relatively high take-off angle of the J-pole is a detriment. While looking around for an alternative, I found the Slim Jim Antenna which seems perfect. I made it out of 450 ohm window line, per KE4NU's plans and attached it to some grey PVC conduit (UV-resistant). Right now, it's mounted inside the attic, so the environment shouldn't be an issue! I'm not convinced that the Slim-Jim's lower take-off angle is really a good thing for an "up high" antenna. Next time I'll trying building a traditional J-Pole out of ladder line. It seems to me that I'm not as interested in gain as I am in coverage, but I'm not sure I'm thinking about it the right way.

Last updated Oct 23 2010 by cak