Portable WSJT (Part 2)


Some assembly required

Once the hardware was in place, I was at the point where I could plug everything together and see how well it worked. The heart of the system is, of course, Joe Taylor's (K1JT) programming masterpiece WSJT, which stands for Weak Signal communication by K1JT. It can be downloaded free of charge at pulsar.princeton.edu/~joe/K1JT/. If the best things in life are indeed free, WSJT is the quintessential example of this old proverb!

When I first tried running WSJT, it wouldn't open because a .dll file was missing. This was eventually traced to the fact that my old version of Windows 95 was not Y2K compliant. A patch downloaded from the Microsoft website fixed the problem. The Y2K insight came from my (somewhat) local WSJT mentor Glen Hansen (KD5HIO), who lives 60 miles north of me in Los Alamos. Glen's insight, enthusiasm, experience, and patience were important to the success of this WSJT rover project.

With the program working, I hooked up the radio gear and verified that WSJT was talking to and listening to the soundcard and also keying the transceiver and brick amp. Soundcard settings were made using the straightforward procedures described in the WSJT manual. The GPS was then plugged into the auxiliary serial port and it was seen that the time synch worked splendidly.

A glitch occurred when WSJT finished its first decode of the receiver noise. The computer didn't crash and the program didn't hang, WSJT simply refused to do any more decoding. No software adjustments I made could get it going again. In desperation, I swapped the serial port connections to put the GPS on the native COM port and the radio interface on the PCMCIA COM port. Not only did this cure the problem, but I picked up another 4 dB of receive sensitivity! Evidently, the serial adapter card was funneling in excessive noise from the GPS that caused WSJT to hiccup. Click here for a photo of the main setup.

Making contacts

Now it was time to move everything to the car. High altitude operating locations are plentiful in the Rocky Mountains but they tend to be cold, windy, and snowy. With this in mind, I have the entire setup with the exception of the antenna inside the vehicle. My rover is a sub-compact, so I remove the front passenger seat and place all the gear there. When I get to an operating site, everything can be set up in about 12 minutes. My first WSJT QSO's, however, were made with KD5HIO while parked in the driveway. Although our stations were too close for meteor scatter, we did complete quickly using both the FSK441 and JT44 modes.

The big test occurred a few days later. On November 17, 2002 I completed my first-ever meteor scatter QSO with Randy "Tip" Tipton (WA5UFH) on 2-meters using FSK441. I was portable in DM65 and Tip was located in grid EL19, about 720 miles away in Edna, Texas. A WSJT screen-shot of the first meteor ping I ever recorded can be seen here. A distinct ping is visible in the time trace, which occured 19.5 seconds into the sequence. Note the decoded text indicating both callsigns and Tip's grid. A .wav audio file of this trace can be downloaded here; you'll hear the distinct FSK441 multi-tone burst at about 19 seconds. Despite being less than 200 ms in duration, plenty of information got through! At this point I knew that Tip had received my message 1 (both callsigns) because he had sent me message 2. Now it was my job to send message 3 (R + report). If I next copied RRR from Tip, that meant he got my message 3; my receipt of his RRR makes the contact complete. Protocol requires exchange of both callsigns, a report of some kind (in this case grid squares) and a "roger" or "R". After I worked Tip, KD5HIO contacted me by ssb and coordinated two more successful meteor scatter QSO's: W3UUM in EL29 and AF6O in DM14 at distances of 790 and 620 miles, respectively. Not bad for the first time out!

My radio equipment is nothing out of the ordinary: 50 Watts into a 5-element K1FO yagi (Directive Systems) at 14 feet. Because of the 50% duty cycle of WSJT (30 seconds on/off) you have be careful not to melt your equipment. My brick amp is rated for 170 Watts ssb with 50 Watts in, but I drive it with only 5 Watts and have added a small muffin fan for cheap insurance.

Since my initial success, I've been on a half dozen portable WSJT expeditions, putting ultra-rare New Mexico grids into the logs of many happy stations, some more than 1000 miles distant! This photo shows the rover during the 2003 Quadrantids meteor shower in grid DM74 just as the sun is coming up. A second beam has been added to get another couple of dB.

Although the DX capability of FSK441 meteor scatter is staggering, it comes with a price -- time. In the late afternoon when the random meteor flux rate is low, it can take the better part of an hour to get enough good pings to complete a QSO. Power and antenna gain can cut this time significantly. If you operate in a region of high contest activity, you'll probably want to restrict WSJT operation to the late night and early morning doldrums when, coincidentally, the meteor rate picks up.

In the January 2003 VHF Sweepstakes, I completed ten scheduled FSK441 meteor scatter contacts on 144 MHz while roving through three grids in central New Mexico. This photo shows the rover setup in grid DM73 with a 6-meter loop antenna (built by N5XZM) also on the mast. The DX contacts, of course, provided me and the other contesters with some very nice multipliers. Most of these QSOs took place in the afternoon using random meteor pings and all were accomplished in less than 30 minutes each. In addition, I used the phenomenal capabilities of JT44 to make shorter distance 6-meter contacts with KD5HIO back in the home grid of DM65. No ssb phone signals could be heard on either end of the path, yet JT44 cut through the noise with little difficulty.

I hope I've convinced you that WSJT is a fairly straightforward way to supercharge your VHF rover operation. If you already own a Pentium class laptop with a sound card, you're almost there. To the best of my knowledge, a rover-to-rover FSK441 meteor scatter QSO has never been accomplished. I'd like to be the first to do it, but I'll need a willing accomplice...any volunteers?

Postscript: Since this article was written, a portable-to-portable FSK441 QSO was completed. Read about it here.

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