Date: Mon, 22 Mar 2010 17:09:20 +0000
From: John Parkins <kvp@bigfoot.com>
Subject: Re: [Amps] how much C in PS is too much?
Hello All,
I feel real inadequate now, knowing I just have normal capacitors in
my SB-220. I must have POWER CAPS!!! to do my 'power buffering'.......
The other thing, if I put twice as many of these in the amp will I get
2kw out of it? After all the guy says twice as many POWER CAPS, double
the power. Why do we mess around with big tubes all we really need are
loads of capacitors. ;-)
## The paltry 25 uf filter cap in ur SB-220 stores exactly 128 joules.
1 x joule = 1 watt second. Now since the SB-220 sucks 2000 watts
dc input on voice peaks, where do you think this energy is going to come from ?
The caps won't supply it... not big enough. 25 uf works out to 3% ripple on
a
SB-220. Being a FWD, the 25 uf only gets..'topped up' 60 x per second as is.
# Run a 1.2 kw out dead cxr, and you will see the wavy line on any rf scope.
You
will also see the last bunch of segments on an AS wattmeter...'dither' . The
lousy
dynamic V regulation affects your TX imd as well, I'm 100% convinced of that.
## Now replace the stock 8 x 200 uf caps in the SB-220 with bigger ones,
like 600-2500 uf each, and you will see the difference on any pep meter.
## anybody that dabbles in ESSB will hear the difference, when the bigger
caps are installed.
## The outfit advertising the big caps for car stereo use is out to lunch. 10
of the
big 10,000 uf caps amounts to only 100K uf = .1 farad.... and good for 100w,
per his calcs. What's needed for car stereo use is 16-25 v caps... and loads
more C. No different than running a 1.5 kw SS ham amp in a car. Batteries
and
caps are 2 x different things. You don't get a huge bang, when you short out
a
battery.
later... Jim VE7RF
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