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

To: Will Matney <craxd1@ezwv.com>
Subject: Re: [Amps] Re: RE: 4CX250B Screen Supplies (Gary Schafer)
From: R.Measures <r@somis.org>
Date: Mon, 26 Jul 2004 04:12:13 -0700
List-post: <mailto:amps@contesting.com>

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

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