Monday, January 5, 2009


I put in about 9 hours playing in the ARRL RTTY RU this last weekend. It was a lot of fun. The results:

40M: 103 QSOs, 29 states/provinces, 5 countries
20M: 16 QSOs, 7 states/provinces, 1 country

I spent a lot of time at the beginning trying to get my 500 Hz filter in the FT-857D working with RTTY. Although I did get things working during the previous Thursday night's NCCC practice, I just used the standard 2.1 KHz filter. That really, really, didn't work during the RU. Strong signals within the wide passband would cause the AGC to kick in and the signal I was trying to copy would go away. I suppose I could have played around with disabling the AGC and riding the RF gain, but it seemed to make more sense to just use the 500 Hz IF filter.

The problem I had was that the passband of the 500 hz filter seems to be centered around 800 hz (a typical CW sidetone/beat frequency), even if you're in LSB or DIG mode. However, MMTTY sends a default mark tone of 2125 Hz. So the filter wasn't passing the frequencies the demodulator was looking for. I was able to change the mark frequency in MMTTY to 915 hz which was within the narrow passband, and I was able to decode signals with no problem, even with W6YX hammering away a few KHz away.

However, once I made that change, I couldn't work anyone, not even local stations that really should be hearing me. I was definitely putting power to the antenna, and I could hear myself on a portable shortwave receiver, but no QSOs.

I finally reconfigured MMTTY to use the other sound card in my computer for output, so I could listen to it, and I discovered that, although I'd changed the receive mark tone to 915 Hz, MMTTY was still transmitting with a 2125 KHz mark tone (see - my music degree comes in handy from time to time!). No wonder I wasn't making any contacts. No matter what I set the frequency to in the MMTTY preferences, the transmit tone didn't change.

What I didn't realize is that I needed to also set the HAM default setting values (directly below the receive settings) - those set the transmit values. As it turns out, I tried clicking on the NET button during the contest, and that solved my problem, since it locks the transmit frequency to the receive frequency. The names of those functions (HAM, NET) don't make much sense to me, but I'm a RTTY noob.

On the RF side, I continue to be impressed with how well my tree-mounted wire vertical works. Of course, I am only able to compare it to my G5RVjr, but I made a lot of S&P contacts on my first call, and worked some JAs and China with no problem. In terms of performance/cost, I'm happy.

On another note, NCCC member Ed Muns, W0YK went to Aruba and operated P49X for the RTTY RU. Ed made - get this - 3,214 contacts in 24 hours. The mind boggles...

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