73

Thanks for the clarification, Bill and Reino.

Is the Q65 ramp amplitude shape and timing documented somewhere?  I couldn't find it in the User Guide or the Quick Start Guide.

Does it vary with sub-mode?

Why is it needed? Reduction of "key-clicks" at the start and end of transmissions?

73,
Steve VE3SMA

Hello Steve,

I was the poster who raised the issue with the FST4(W) waveforms in this forum and in the RSGB LF group.  You can see the later part of the discussion here:

https://wsjtx.groups.io/g/main/topic/79269122#20188

The problem arises because, at some point in the chain, the analog drive signal has to be converted to digital form, preferably with as little jitter as possible.  Typical squaring circuits have a dead or indeterminate band - however tiny - and, with very slow envelopes, produce erratic pulse drive to the (very widely used) Class D or E PAs, the designs of which typically requires a well-tempered pulse train.  As you see from the previous discussion there are several solutions possible, the most satisfactory being the setting of the environment variable as outlined by Bill.

I haven't tried Q65 yet but can do so in the next week.  Whether there's a problem will depend on the how slow the envelope rise and fall is.  I agree it'd be handy to have some descriptions or, better yet, sketches of the various WSJT mode signals.

73, Peter.

Hi Peter

Yes, I saw your posting earlier...an interesting thread.  I am not sure I understand what the reasons are for the ramp up and down.  My interest in Q65 is really for VHF and up, where Class D and E amps are mostly impractical (though getting closer over time as technology improves), but running a Class C amp (or class A or AB in hard saturation) is easy.  I'm guessing there would be no equivalent issue with the ramps in this case, though I suppose there might be a momentary increase in dissipation.  But it would be helpful to know the waveform and what one gives up by eliminating the ramps.

74,
Steve VE3SMA