Date: Fri, 10 Nov 2017 08:01:03 -1000
From: Merv Schweigert <k9fd@flex.com>
To: amps@contesting.com
Subject: Re: [Amps] Amplifier for 630 meter band
<Lot of work for naught.. the power limit on 630M is 5 watts and even
with a very poor antenna
you only need 100 to 200 watts to get 5 out of the antenna. A single
or two MOSFET amplifier
will do that no problem and will fit in a mini-box.
NO3M has converted a SB-1000 think it was, he used it under his
experimental license which has
higher power limits. Google NO3M and there are pictures or some info.
There are a couple others on line that converted tube amps. Almost none
use them now.
MOSFET amps are doing 80 to 90 percent efficiency, why waste a tube amp
at 50 to 60
percent.
No high voltage, no fans, much better ways to go these days,
especially on 630M
73 Merv K9FD/KH6
## what config are they using to achieve 80 to 90 % eff ?? Is it class D or
E or similar ?
## 68-70% eff on 40m is easy, in class AB on any GG triode...ditto with 80 +
160m..
And thats in SSB linear mode. Increase the bias V a bit, till idle current is
down to just 10-25 ma,
and eff will go up even more... like typ 74-80 % eff.
## You can NOT run a GG triode at zero idle current in class B, or with
more bias V, still zero idle current, but now class C, or u will get key clix
on CW.
## if u only run 5 watts ERP, nobody is gonna hear you at the best of times.
You cant
work em, if they cant hear you.
Jim VE7RF
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