[Elecraft] JT65A output power variations.

[Julian, G4ILO]

Richard Ferch wrote:
> 
> However, RTTY and many FSK or MFSK-type modes (including JT65A, I 
> believe) feature a single constant-amplitude carrier that is stepped 
> between tones. When there is only a single tone being transmitted at any 
> time, compression does not cause intermodulation; it causes harmonic 
> distortion (odd-order harmonics), which can be eliminated by filtering 
> (the transmitter's crystal filter). The net effect after both 
> compression and filtering should be a constant amplitude signal. I 
> believe this is why JT65A users can safely use compression.
> 
Hmm. As I wrote in my blog a while back (
http://www.g4ilo.com/2009/10/embarrassing-moments-in-ham-radio-1.html ) I
once inadvertently did an experiment that proved the crystal filtering does
not do a perfect job of removing the harmonics of a distorted RTTY signal.
And surely the amplitude is not constant as seen by the ALC due to the
effect of the ripple. If it was constant the ALC wouldn't change so it would
not cause any harmful effects.

But heck, I'm just a software guy. Hopefully someone like Lyle who actually
knows what he is talking about will chip in on this.

-----
Julian, G4ILO. K2 #392  K3 #222.
* G4ILO's Shack - http://www.g4ilo.com
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