Sunday, June 13, 2010

Back to front

Last night for the first time in a very long time I operated RTTY. I made ten contacts in the BARTG RTTY 75 contest. The reason was that Elecraft had released a beta version of firmware for the K3 that enhances the built-in DSP modems to support the 75baud RTTY mode that was being used in the contest. Now that the K3 also supports a way to get decoded text into a computer program I thought it would be fun to give it a try.

For those unfamiliar with the K3, the transceiver boasts a built-in Morse decoder plus DSP based modems (encoders and decoders) for PSK31, standard 45.5baud RTTY and now 75baud RTTY. As the K3 doesn't allow direct input from a keyboard, the usual way to use this facility is to send text using a Morse paddle and read received text on a scrolling 7-character window of the K3 display. However, using a program like KComm it is possible to send and receive text using software commands over the CAT interface as well. Since, like most things that require good motor skills, I'm hopeless with a paddle (or key) at anything much above 12wpm, that's what I did.

I installed the new firmware and it decoded 75baud RTTY signals perfectly, so I waited for the contest to begin. After it did, I soon found that although people were hearing me they weren't decoding me. I got lots of QRZ?, ??????? and SRI NO PRINT. I started to get frustrated and began thinking that RTTY is an obsolete mode that has no place in the 21st century because I know I could have made contact with these stations easily using PSK31 and a fraction of the power.

I decided to switch to soundcard mode and use Fldigi to try to make some contest contacts, and then found that people were replying to me on the first call! So clearly there was something wrong with the RTTY being generated by my K3.

This morning I tried receiving some of my transmitted RTTY using the FT-817 and Fldigi on my NC-10 netbook. When the RTTY was generated by Fldigi it was received perfectly. However when it was generated by the K3 I received gibberish unless I switched the K3 to REV DATA mode (i.e. reverse sideband.) Since I was receiving the RTTY perfectly OK using the normal sideband I presume that the K3's transmitted RTTY was reversed. I have reported it to Wayne and await comments.

Unfortunately I did have some problems with KComm as well. After a while, it started aborting the transmission of any macro after the first few diddles. Like many programs, it has grown to the point where it is hard to understand what is going on any more and my interest in programming has fallen off a cliff in the last few months. I don't know if I will ever get around to fixing the problems and releasing the final version. I do like using it, and KComm is the only program that really supports the K2 and K3 properly because it doesn't treat them like a Kenwood TS2000 (whose command set it nominally shares) but was written to take account of the way these radios actually work.
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