Hi Steve,
Many water cooled GS35B amplifiers are in use, mostly on 70cm. Do a Google
search for "water cooled GS35B" and a lot of information will come up.
The temperature concern is a non issue as the only requirement is for the
cathode to reach a proper temperature to emit electrons. All of this happens
inside a vacuum much like a thermos bottle for hot/cold liquids.
An added benefit of water cooling at the higher frequencies is a big
reduction in frequency drift of the plate resonators, especially the strip line
type. When the are heated due to close contact with an air cooled anode,
they change dimensions at the rate of around 20 parts per million per degree
C. While that may not sound like much, a high Q resonator can move off
frequency enough in a few seconds to drop the power out put 3 dB or more. It
is
not enjoyable to operate cw sending with one hand while watching power and
adjusting the plate tune with the other hand. Yes, I have been there and
done that.
True coaxial resonators are much more frequency stable (and efficient) but
that is another story/topic.
73,
Gerald K5GW
In a message dated 3/14/2016 9:44:30 A.M. Central Daylight Time,
stevewrightnz@gmail.com writes:
I am thinking of liquid cooling VHF/UHF GS-35b tubes to dodge noisy fans
and and tuning drift.
But what will be the situation with operating these tubes at lower
temperatures? I cannot see that they have a rated operating range, just
a maximum seal temperature.
Steve
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