[NLRS] Class C amp and digital modes

[Chris Elmquist]

On Sunday (08/10/2025 at 10:58PM +0000), Jon Platt via NLRS wrote:
> A technical question for the brain trust.  Because slow digital modes like FT8, Q65, and WSPR use a single tone one at a time, its my understanding that it would be OK to use a Class C amplifier with these modes.  Fast modes like MSK144 use multiple tones at one time so no Class C there.  Right? 

I'll wait to see what the rest of The Trust says but my understanding
is that it is not the number of tones that matters but whether or not
there is amplitude modulation of any of those tones.

FT8 as an example, is 8-ary FSK... meaning there are 3 tones transmitted
in parallel to represent 8 different possible code combinations.  So you
have three FSK carriers together on the transmitted signal.

So, because it is FSK, I think it is possible to use a class C amplifier
because you don't care about how loud those tones are, just that their
frequency is faithfully reproduced after amplification.

A trivial example is pushing DTMF tones through your NBFM mobile or
HT radio.  There's two tones there and that works through class C amps
on the backend of any of those type of transceivers.

Other modes that use any sort of amplitude modulation of the tones would
not survive class C amplification I believe.

Chris  NØJCF
-- 
Chris Elmquist