Ron Castro (N6IE) said:
"Since PSK-31 works by shifting phase, the amplitude variations caused by ALC
shouldn't have any significant effect on either the IMD or readability of
this signal."
------------------------------------------------------------------------------------------------------------------------
Ron, we are going to have to disagree on this one. Anytime you introduce a
nonlinearity into the system producing PSK31 signals you will generate
unintended sidebands. You may do that by overdriving the audio stage or the PA
, or you can do that by introducing any nonlinearity into the RF amplifiers,
including the final stage. Certainly, massively overdriving the signal, as
you described, is one way to cause a problem. Of course, using speech
processing - which introduces distortion into the signal, - will also cause
serious sideband distortion and excessively wide signals. The problems caused
by ALC making the final non-linear is probably a function of how much ALC
action is invoked. But I think any distortion isn't helpful in this mode and
creates a wide signal that isn't appreciated by other users.
This is a pretty good presentation on PSK and tuning a rig (Worth looking at)
http://kk7uq.com/html/download/IMD%20Presentation.pdf . I think you will always
find that papers on this mode recommend low, or if possible, NO ALC action.
73. Merle - W0EWM
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
|