Steve's Radio Page SW40+ Project

Don't expect to be impressed with this page yet. Today, 4/22/2006, was my first day playing around with configuring my transceiver and PC to do RTTY. However, I was so impressed with my progress that I felt I had to put something down. So this is the beginning of my RTTY page.

I am currently doing CW nets to get my CW experience up. I am signing onto the 3905 Century Club 40 meter CW nets, usually three times a week. They also have a lot of nice awards. So I am collecting contacts, but I am lucky to get one or two contacts per night, since the number of CW ops checking into the nets is about on average 10 or 12. This is in contrast to the SSB nets that have had more than 100 check ins at a time. Anyway I wanted to get more into awards chasing without using a microphone so I figured it was time to start to master RTTY.

At first I had no idea how to proceed. I am using MixW for PSK31, but could not even read any RTTY signals so I had to start from scratch. My first task was aligning my radio's RTTY filters. Yes, most store bought radios, you just turn it on a press a button that says "RTTY", but I am proud to say I built one of the best radios available today, an Elecraft K2. One of the great features of this radio is that it has never gone obsolete. I built it about 7 years ago as a CW only rig. I then added a SSB module later on. They have sold nearly 5500 K2s since they were first introduced, and mine is serial number 402. I recently upgraded it to 100 Watts and its has a 20 Watt and 150 Watt tuner, and a really good DSP unit. So it has really has never gone obsolete. Anyway the new firmware now has a provision for separate RTTY filters: four that are based on the variable IF crystal filtering, and four that are based on one of the best audio DSP units ever made for amateur radio. The reason that audio DSP was chosen was because it is less expensive than IF DSP, and the K2's IF design is so good that ID DSP would really not help much. Anyway, I just adjusted the IF crystal and audio DSP filters for a center frequency of 1500 Hertz, and the results appear to be terrific. I have some pictures below to illustrate this.


This is a waterfall display from MixW showing the crystal filter widths for the RTTY mode. The widest band is basically the fixed seven crystal SSB filter. If you look at this filter in Sprctrogram you would see that it has a very good shape for SSB. The next three bands are 1300, 1000, and 500 Hertz nominal, respectively. The K2 lets you program the center frequency and bandwidth for each setting.	These are the audio DSP filter widths after I specified the widths and center frequencies. Please realize that the filter adjustments are made by viewing the MixW or Spectrogram screen while you fiddle with the settings on the transceiver. This way you get immediate visual feedback on how effective the adjustments are. After you go through this procedure you know exactly how good your radio is, because you have seen the filter shapes on the PC screen. Anyway, the bottom width is wide open, where the DSP filter does not really influence the shape of the filtering. The next three widths are nominal 1000, 300, and 100 Hertz settings.

This is the MixW macro command to toggle thru the crystal filters from the PC.	This is the MixW macro command to toggle thru the DSP filters from the PC.

This shows the K2 digital filters after they where adjusted for a center frequency of 2110 Hz.	Here I show the tones injected into the sound card by the PK-232 for Pactor mode using the CAL command. The center frequency is 2110 Hz and the offset is 200 Hz.

Here I show the spectrum when the K2 is set up for Pactor.