[TenTec] O2 output level with PSK aux

pfizenmayer pfizenmayer at qwest.net
Wed Feb 11 21:50:43 EST 2009

Bob - I think your thought about 2nd harmonic may be a very significant 
factor. I know that in my original Orion 565 I was trying to do a AF freq 
response watching the RF amplitiude on a meter - Things looked screwy at low 
frequencies up to about 100 cycles -Then I hooked up my scope and looked at 
the RF envelope and there I could see the generation of very significant 2nd 
harmonic with AF input freqs under 100 cycles . Above 100 cycles that went 
away. I did not try to figure out where it was coming from as I was not 
really interested in USING the Orion with AF inputs under 100 cycles -it 
just showed up in testing . I have not looked at my OII to see if it does 
the same .

The ne thing that went thru my mind is that the ESB guys should love that - 
it was a trick the old AM radio designers used to use to make the bass sound 
better .

73 de Hank K7HP

> In thinking about this a bit more, if the slow sine modulation is seen 
> while
> using the PSK mode then I would suspect the 2nd harmonic, being 62 Hz, of
> the PSK signal beating against the 60 Hz line freq producing a 2 Hz
> difference and modulating the PSK signal.  Now the real question, if 
> indeed
> it is the 2nd harmonic of the 31 Hz PSK signal, then where is it being
> generated?
> Typically 2nd harmonics come from a single ended stage that is incorrectly
> biased or is being over driven.  Sound card, interface box, input stage to
> the radio are all suspect and good places to start looking.

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