[Amps] Re: RE: 4CX250B Screen Supplies (Gary Schafer)

[R.Measures]

On Jul 25, 2004, at 9:49 AM, Will Matney wrote:

> Exactly, and is my point here. Yes, two tones do produce some variance 
> but that is what the test was around. What happens when you add voice 
> with all the frequencies and harmonics like I'm speaking of? Does the 
> IMD raise or stay the same? With the two tones, you'll have those two 
> frequencies, their products from each because of mixing and some 
> harmonics from each of them. Each multiple with a lower voltage than 
> the center frequency which I assume your speaking of varying the 
> current and voltage. Keep in mind though that still each are at a 
> constant peak to peak voltage (each frequency with harmonics and 
> products lower) because of the generators output and are unchanging 
> each cycle. The voice will cause all these other frequencies to vary 
> and thus be more "wide" spread than the test tone and the incoming 
> peak to peak voltages each cycle changing. It was always my 
> understanding that this is where the IMD problem came from. The two 
> tone test shows so much, but like you said, the voice signal may be 
> unmeasurable.

Measuring the IMD level of a voice signal involves setting up the A/B 
VFOs c. 4.5KHz apart on a separate receiver.  Set VFO A on-frequency.  
Set VFO B 4.5KHz higher for a LSB IMD measurement, or 4.5KHz lower in 
freq for a USB measurement.   Switch to VFO A, say Ahhhhhh into the mic 
and note the S-meter reading.  Switch to VFO B, say Ahhhhh and note the 
S-meter reading.  If you know the db per S-unit calibration of the 
S-meter, you then know how many db down the total IMD is.

> However, I would like to know what it would be by using the different 
> regulators with voice modulation. After all, we don't speak in two 
> tones but all of them with differentiating volume. I'd still about bet 
> it will raise it.
>
> Will Matney
>
> "Multiple tones could also be used rather than just two tones but that 
> gets tough to unscramble as many more products are produced.
>
> 73
> Gary  K4FMX"
>
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>
Richard L. Measures, AG6K, 805.386.3734.  www.somis.org