[Amps] RE: 4CX250B Screen Supplies

[R.Measures]

On Jul 27, 2004, at 1:17 AM, peter.chadwick at 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.  www.somis.org