Date: Mon, 09 Aug 2010 15:09:53 -0400
From: Roger <sub1@rogerhalstead.com>
Subject: Re: [Amps] How do you - powering a SS amp with a capacitor?
On 8/9/2010 11:49 AM, Joe Subich, W4TV wrote:
> > However, by putting a very large capacitor AT THE AMPLIFIER, you can
> > use smaller wires and a smaller power supply. The capacitor charges
> > during periods of low current draw and then supplies power when
> > needed.
>
> This only works with CW and unprocessed SSB. Heavily processed SSB
> and digital modes have a sufficiently high duty cycle (low peak to
> average ratio) that the capacitor is not able to completely charge.
## agreed.
>
>
Just watch the plate voltage drop in a typical amp as you add
compression. Unprocessed SSB in a typical amp may show 100 volt drop
while heavily processed with compression and clipping might show a 300
volt drop. Coming from a different direction, look at the PEP output.
An amp may be capable of 1100 watts continuous carrier, key down, but it
might actually make the 1500 PEP legal limit with unprocessed SSB. NOTE
both examples are highly dependent on the individual amp so YMMV doing
your own experiments. <:-))
## Try increasing the value of the filter cap in the B+ supply and you will
get a real eye opener.,,[ more pep out]. The typ sb-220 with say 3 kv no load
and a 25 uf stock filter cap. That combo = 112 joules. That's 112 w for
one second,
ccs. And along comes joe ham, with his SB-220, who wants to suck 2 kw
dc input, on voice peaks. You can probably do it too..as long as the duration
of each voice peak doesn't exceed 50 msecs.
## double the C in the AL-1500 and the pep out goes up another 100w. None of
these
amps have a low enough ripple for my liking. The Sb-220 and L4B are
3%..stock.
By doubling or tripling the stock C.... you can get the ripple down to 1-2
%... and
achieve better dynamic regulation...= more pep out..even with processed SSB.
## The problem with these typ table top amps is..the caps don't store enough
energy to begin with. Use a string of 2500uf caps..and the B+ won't even
flicker.
later... Jim VE7RF
73
Roger (K8RI)
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