>K3 FSK has always had a small amplitude difference between mark and space.
>The transition has always been abrupt, Photo 1. With the new beta software,
>the transition is much more gentle, Photo 2. Bravo!
Hank,
As you are aware the only reason you can see that transition in the RF
envelope is because your tones are unequal by about 1 dB, assuming the vertical
scale is linear on your scope pictures. That's a real issue since the amplitude
difference between the tones because that is going to look like a fixed
selective fade to whomever you are communicating with. That's going to make a
noticable difference in character error rate for weak signals, especially if
the other person's demodulator is not using an ATC. I've seen some of this
same kind of thing when someone is using AFSK tones near the edge of their TX
passband, and the roll-off of the filter causes this issue. You probably know
all this already. It sounds a little strange, but I wonder if it could be
caused by a nasty passband ripple in the TX IF filter. One dB ripple over 170
Hz seems like a bit much for a filter that is nearly 3KHz wide.
I don't see that amplitude difference on my radio with either of the firmware
versions, which makes me suspect it might be something in your hardware. (I
can measure a difference, but it's consistent with <0.1dB ripple at the center
of the IF filter). I have the 8-pole 2.8 KHz filter in this radio, for
reference.
Anyway, that's a datapoint and some speculation for you if it is helpful.
Andy K0SM/2
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