Roy, Have you checked this out with the control ops? I don't know but are there any duty cycle issues to worry about? And given that a linear transponder has a finite power budget what does it do to the other users? Maybe not a big deal but I wonder if the sys ops for these birds have any words of wisdom for us before we all start cranking up MMSSTV and banging away. John
I have not. However I did just try it out and was monitoring the pass band and did not see any adverse affect. In fact, there were QSO's going on simultaneously that were very strong (stronger than my signal, for sure).
At one point, it did seem as though somebody may have been doing something that was affecting the downlink (but it wasn't me as I wasn't Tx'ing at the time) - as it was a very wide signal that sort of sounded like it could have been SSTV splatter. Could have been local QRM, too. At the start of the first pass I received a partial image from another operator that was very nice (I just didn't pick up the signal until the image was completing). I also decoded my downlink after the pass and one came in very nicely and the other was recognizable but I think a frequency shift caused a decode hiccup that introduced interesting patterns and colors. I didn't get any "good" decodes from the second pass, but I'm wondering if I can do some post processing of the recorded file to shift the audio frequencies (they decode, but again stange colors and patterns - but can still make out text on solid backgrounds).
I took some screen grabs of the passband during transmission, and it looks pretty good. At one point I had my power down to "3" on my 706MKIIG, which should be about 7 watts out of the transceiver (through 50 ft of RG-8X, an auto switching LNA, MFJ 916b, and another 6ft of LMR-240UF) and I was still getting in (and heard on the downlink).
I'll reserve further linear SSTV operations until we've had a chance to discuss the opportunity (and/or abuse). It is definitely a challenge, and could be a lot of fun. Not sure how possible it would be with manual tuning, though.