Carl wrote:
>Find out where the gamers and overclockers get their compounds; Chile
>is no exception.
>
Good point.
We aren't the only ones doing this, and we can learn from experience in
other areas.
Overclockers use water cooling with confidence, in a location where any
leak would be disastrous. Parts such as pumps, header tanks, flow
sensors and 'radiators' (secondary heat exchangers) are readily
available. The only special part for SSPAs would be the heat sink.
One of the major advantages of water cooling is that the various parts
of the cooling circuit can be physically separated. This makes the
layout extremely flexible, unlike air cooling which requires the
transistor to be attached to a large heat sink with blowers, making one
very large 'lump' of hardware around which the rest of the amplifier
must somehow be arranged.
A British ham has designed a compact lightweight 500W DXpedition
amplifier using a water cooling plate, but all the other parts of the
cooling circuit come from the overclocking market. With a compact
rear-mounted secondary heat exchanger, the volume of water required is
little more than the volume within the cooling circuit, so the water
reservoir is tiny. This cooling circuit has been extensively tested at
DXpedition duty cycles and it works fine. Further details are not yet
available (it isn't my story to tell) but it does show that a water
cooled SSPA can be engineered both simply and reliably.)
Another observation: if you have ever disassembled a CPU from its
heatsink, another thing to note is that the film of heat transfer
compound is extremely thin. The problem for manual application is to
replicate this, which usually means smearing on the compound and then
wiping almost all of it away.
As Carl mentioned earlier, there's at least 20 years of good experience
with water cooling of tube amps among serious 1.3GHz operators.
Typically these amps use 3CX100 tubes in singles, pairs, fours, sixes or
even eight at a time. The key article, which covers all the relevant
points about water conductivity and monitoring leakage current, was by
N6CA; it was in the ARRL Handbook for many years and can surely be found
on the web.
Regarding the size of the water reservoir, another 'data point' is a
moonbouncer who uses a large plastic garbage can with no other secondary
heat exchanger. Starting from room temperature, he can operate
intensively for a whole weekend before the water is becoming a little
warm. There are rest periods of 8-10 hours between moonset and the next
moonrise, but this experience does show that secondary heat exchangers
aren't always necessary.
What all this adds up to is: let's not discuss this topic as if we were
the first people ever to think of it - of course we aren't! There's
loads of information and experience around, and most of it is readily
available on the web.
--
73 from Ian GM3SEK
http://www.ifwtech.co.uk/g3sek
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