Good comments here Bob; you've nailed some relevant points here.
The GS35B does indeed need a higher plate voltage / plate load impedance to
achieve parity in efficiency with the 8877; complaining about achieving
circa "only" 55% efficiency and a few extra watts of exciter drive is
splitting hairs; particularly in a GG AB2 SSB linear.
At circa $120 the NOS GS-35B represents the best bang for buck in the 1500W
plate dissipation triode tube class; costing a meagre 10% of that of a new
8877 from CPI/Eimac, or 15% of the cost of an excellent Chinese clone.
Most affordable key RF components for building QRO amps like tubes, vacuum
capacitors, vacuum relays, doorknob capacitors, roller inductors, etc are
all made by non-USA countries. If it weren't for the China tube companies
producing affordable clones of the popular ham-radio tubes and Russian NOS
surplus parts, then readily available tube amplifier components would be a
thing of the past...or the exclusive domain of the wealthy ham.
Cheers,
Leigh
VK5KLT
-----Original Message-----
From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
Behalf Of Robert Briggs
Sent: Monday, 30 July 2012 5:11 PM
To: amps@contesting.com
Subject: [Amps] 3CX1500A&/8877
Interesting comments re the two types of tubes 8877/GS-35B...I have
built six amplifiers using the GS-35B four on 160 meters and two on 6
meters...I have found that to make the 35B reasonably efficient you need
at least 3500 volts under load...
I live in VK and we don't have the opportunities to buy 8877
pulls...When one considers cost then the GS-35B is way ahead at
$120..The efficiency at 3500 volts is around 55%....You must use a tuned
input to get the best from the tube..Who cares if you need a few more
watts to drive the 35B....Pretty well all transceivers these days have 100
or 200 watts output..
There always seems to be a bias on here by some people regarding
anything that isn't made in the US...Hams are generally looking for the
cheapest way to build amplifiers and other gear and there is a ready
market out there of excellent quality components made in other countries
other than the US...
I spend much of my time custom building amplifiers for VK hams and a
large majority of the components come from suppliers like Dr Alex Gavva
UR4LL...I have never had a faulty tube or capacitor from that source...
Bob..VK3ZL..
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