----- Original Message -----
From: "Tom Rauch" <w8ji@contesting.com>
To: <g3rzp@g3rzp.wanadoo.co.uk>; <amps@contesting.com>
Sent: Thursday, September 27, 2007 8:05 AM
Subject: Re: [Amps] How much electrolitic for a HV supply ?
>> But is the requirement ripple reduction, or the ability of
>> the HV supply to hold up for short peaks?
>> The capacitor releases 0.5 .C.Ve2 (one half C times V
>> squared) joules where V is the drop in the HV. That's
>> also equal to coulombs/sec, which is I times t.
>> So you can equate these to figure how much capacitance is
>> needed for a given AC supply impedance and frequency for
>> an amount of ripple. But if you're talking of allowing a
>> different voltage drop over a 50 millisecond speech peak,
>> you get a different answer, and that's where a big
>> capacitor holds up better. It also can show up a lot
>> better on a 2 tone test as the tones get closer together
>> in frequency, although I think we all agree that a 2 tone
>> test is not the be-all and end-all of test methods. But in
>> terms of ripple, the bigger the ESR, the sooner you get to
>> the stage of diminishing returns.
>
>
> If the supply is that loose, you better use a battery.
>
> The problem isn't only a 50mS time constant for the lowest
> speech tones, the problem is a cycle per second time
> constant for the syllabic amplitude gaps and level
> variations.
>
> Increasing the electrolytic size can actually make an amp
> less linear under some speech conditions if the supply is
> loose from a very poor transformer. The cure is to not use a
> high ESR transformer on SSB.
>
> 73 Tom
RCA went as far as specifying PS C in their spec sheet for the 8122 family.
Carl
KM1H
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