[Lowfer] CMSK Receiving Hints

[w1tag at charter.net]

Referring to Jay's message today, I do have a few receiving tips for those who may want to copy his signal tonight.

We are really impressed at this method's ability to provide a QSO-type mode in a 50 Hz BW for use with a non-linear PA. It is quite resistant to static crashes, and handles fading well up to a point. It does seem to resync more quickly than MFSK 16 or 8 if a signal is lost in a fade. The 7.8 baud option is, of course, very slow, but suggests possibilities for beaconing or repeated messages. It does have additional fade and crash tolerance. 

1. This is Beta software, and some things are just not there, yet. Be patient! In particular, it does not save some settings, so you get to input them every time you fire up. A fix is promised.

2. Sampling rate appears to be important, particularly if it differs considerably from the default 8000 Hz. With the loss of Loran-C signals in the U.S. and CA, my on-line descriptions of meauring actual sampling rate are out the window! But remember that WWV (received in AM mode)  has nice 500 and 600 Hz tones that can be used with Spectrum Laboratory. I'll try to cook up a description today if time permits.

3. I had slightly better results with my receiver filters of  500 or 250 Hz than with the wide-open USB mode. Your results may vary. In any case, I have been keeping my R75 in CW-Rev mode, and clicking on the CMSK waterfall at my BFO frequency (800 Hz). But you could also use the USB method of setting your receiver 1 kHz low, and keeping the default 1 kHz on the waterfall.

4. The "Fine Tune" slider under the eye display can be used to center the frequency excursions from left to right. 

The Help section should give you enough info to get started. 

John, W1TAG