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Re: [Amps] RE: 4CX250B Screen Supplies

To: peter.chadwick@Zarlink.Com
Subject: Re: [Amps] RE: 4CX250B Screen Supplies
From: R.Measures <>
Date: Wed, 28 Jul 2004 03:24:07 -0700
List-post: <>

On Jul 27, 2004, at 1:17 AM, peter.chadwick@Zarlink.Com wrote:

Some professional tests use a very narrow spacing between tones - as low as
30Hz - to simulate the syllabic nature of voice, and to exercise the power
supply regulation. Another approach, which, if I remember correctly, has
been advocated here by Tom, W8JI, is to use a three tone test with two of
the tones very closely spaced. As Steve, G8GSQ says, the screen current
varies at a frequency dependent upon the tone spacing.

Because of the peak to average nature of a voice signal, it isn't easy to
relate the performance on a two tone test with that under voice conditions.
The advantage of a two tone test is that it does (or should!) give a number
that can be reproduced in testing by other people.

Peter -- Should, yes. With 30Hz or so tone spacing, it's going to take an incredibly capable spectrum analyzer to separate and measure the 3rd and 5th order products. If the thing we are concerned about is on-the-air rotten splatter from voice modulation, why not measure splatter from voice modulation by listening to the adjacent channels with another receiver? Sure, a precise ± 0.1db measurement is not going to happen, but, ± a couple of db accuracy is good enough in this case. // cheers

Richard L. Measures, AG6K, 805.386.3734.

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