[Amps] liquid cooled Amplifier coolant recommendations

[TexasRF at aol.com]

Fletch, I have been using the same cavity amplifier for several years.  
Walmart has distilled water for about $.75 per gallon that works just fine. As  the 
water ages, the screen current tends to creep up which provides a simple  
monitor for the water condition. I typically exchange the three gallons of water  
about every two years.
 
In my unit, the two water hoses pass through a metal rear panel by means of  
brass fittings fastened to the grounded panel. I had to increase the length of 
 the two hoses to about two ft each to prevent excessive screen current due 
to  the small water conductivity.
 
A couple of years ago I experimented with adding a small amount of  
antifreeze to the water and that was a disaster! Apparently the antifreeze  solution 
had more than a little conductivity and caused the screen over current  trip 
circuit to activate immediately upon turn on. It took a couple of water  
flushings to restore the proper operation.
 
73,
Gerald K5GW
 
 
 
 
In a message dated 5/16/2008 3:51:06 A.M. Central Daylight Time,  
fletchv3 at comcast.net writes:

I am in  the process of getting a water cooled GS-15B cavity on line and I
wonder if  the group has any recommendations on coolants.  Distilled water  is
typically of unknown provence, so you are never sure if it is really  low
conductivity unless you measure it. Somehow the idea of 1700-2000V on  water
of unknown conductivity just bothers me. (silly me!)  I have  heard that some
Radar systems and high power lasers use a special ethylene  glycol for a
coolant.  I wonder if anyone in the group has any  experience with such
coolants and if they can recommend a source for  same.

Thanks and regards 
Fletch 
K3JYD 
FM18  

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