On Mar 11, 2005, at 9:42 AM, John T. M. Lyles wrote:
> Look up Thermacore in Lancaster PA, they are
> making some innovative heat pipe cooling loops
> for integrated circuits and other applications.
>
> As for adding sodium or other ions to DI water:
> this will increase the conductivity greatly and
> cause current flow in the hoses.
Adding sodium to water is one way to light a cigar.
http://www.pc.chemie.uni-siegen.de/pci/versuche/english/v44-1-1.html.
> Eventually leads
> to migration of the copper and brass fittings, as
> deposits along the inner walls of the hoses.
> Also, this will erode away the fitting where the
> hoses connect to the tube from the mA flowing. In
> our water cooler RF amplifiers, I try and keep
> current under 250 uA in the hoses if possible.
> When we have large OD hoses like 2 inches or more
> (for big toobes) this is a problem, and it
> requires length to get enough resistance between
> the tube and ground, in each hose. In a hose such
> as 1 inch PEX (which is sold at Home Despot and
> 'Lows' for home plumbing) about 60 inches are
> required with 5 Megohm-cm water conductivity
> (very clean). We trip HV interlocks on many of
> our systems if the Foxboro conductivity meter
> indicates below 5 Megohm-Cm. This indicates time
> to change the Culligan bottles. Call Culligan
> man. For smaller hoses like 1/2 and 3/8 inch
> (more likely at the 5 kW and under level) lenght
> is shorter. Just treat the hose full of water as
> a big resistor in your ohms law analysis.
>
> For occasional use, be sure that the water
> quality is still good. There must be test kits
> available? If you open the system to air,
> dissolved oxygen is a bad thing. We use
> deoxigenator bottles as well as RO bottles. We
> keep it below 5 ppb as recommended by CPI/Eimac.
>
> Thales tube company sells expendable electrolyic
> anodes which are placed inside the water fittings
> at the connections to their tubes, so that you
> sacrifice them, and run higher conductivity
> water. It can be as low as 100 kohm-cm using
> these devices. But they need to be checked
> annually in 24/7 operation, as the tips will
> erode away to below the edge of the brass
> fitting, then you expose the fitting to
> erosion/corrosion.
>
> One more point, do not use regular steel in the
> plumbing for a DI cooled loop. It must be copper,
> brass, or stainless steel.
>
> I agree that water cooling is a proper subject
> for some QRO systems. Probably has been beat to
> death here this past two weeks though! Try it,
> you'll like how quiet it is. BUT, as you all
> know, HV and water don't like to mix.... However,
> for solid state, its relatively painless:
>
> I helped design and install two 2.8 kW CW water
> cooled amplifiers at 805 MHz, at work here in
> 1994-97. They replaced a room full of RCA
> Cermelox Tetrodes in cavities, which had been
> made obsolete when Burle Industries quit making
> the tubes. Our complete 40 dB amplifier with
> power supply fitted in one tall 19 inch rack. We
> used a slug of MRF899 bipolar transisitors, as
> LDMOS wasn't the rage then. You can read about
> the amplifier and see photos in the 1998 RF Expo
> Proceedings from San Jose, or send me a note and
> I can forward a copy.
>
> 73
> John
> K5PRO
>
>
>> Will writes:
>>>
>>> Personally, I dont see anything wrong with the posts as they
>>> pertain directly to water cooled tubes. If some addative can
>>> be used to cool a tube better, this is an amp forum, and it
>>> should be discussed. This especially if the addative can
>>> prolong the life of a very expensive tube.
>>
>> Neither do I see a problem. Fact is, by this time next year
>> I expect to see a water cooled solid state amplifier available
>> at Dayton. There should be some 120 - 200 volt transistors
>> available at a reasonable price per watt by then the problem
>> will be keeping them cool with a typical heatsink/fan. A
>> water cooled substrate (copper block) with a small closed loop
>> system would make for a very nice package.?
>>
>> I hope we see some 1500 Watt (CW) output 100% duty cycle solid
>> state amps (4 transistors) at reasonable prices (competitive
>> with the Ameritron, TenTec, Commander, etc.) within the next
>> two or three years.
>>
>> 73,
>>
>> ... Joe, K4IK
>>
>>
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Richard L. Measures, AG6K, 805.386.3734. www.somis.org
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