[Amps] Tube Cooling..

[Roger]

On 11/25/2010 12:52 AM, Bill, W6WRT wrote:
> ORIGINAL MESSAGE:
>
> On Tue, 23 Nov 2010 20:28:52 +0000 (GMT), DAVE WHITE
> <mausoptik at btinternet.com>  wrote:
>
>> Whilst it may seem counter-intuitive to blow cooling air DOWNwards I've seen tome successful Eastern European designs whereby large fans blow air directly downward onto the top of the tubes so that the air runs by the fins.
> REPLY:
>
> The trouble with that approach is you have hot air blowing down over the
> tube seals and socket. Not good. Anodes by themselves are relatively
> unaffected to heat compared to the seals and socket.
There are several tubes that are designed to have air blown *down* over 
the top seals. . One is the 833 and the other is the Russian GU81M.  The 
833 even gives specifications for proper cooling of the top seals with 
downward flowing air from a given size nozzle at so many CFM.

These tubes have two sets of specifications. One for no forced air and 
one for forced air. Both run considerably more power with forced air, 
but a pair of GU81Ms will run about 3KW in contest operation with no 
forced air which is considerably beyond their official ratings.  OTOH 
their ratings drop off rapidly from 40 meters on up, but they are good 
all the way to 6-meters IIRC, just not at 3 KW out.
One ham stated he has been running a pair of the things like this for 
over 15 years in contest op.  The nice thing is...no fan noise at all.  
You could likely keep your coffee warm and fry breakfast eggs on top of 
the cabinet saving time away from the rig during contests.<:-))

I need to find a one or two pair of sockets for the GU81Ms.

73

Roger (K8RI)
> Better to have the cool incoming air flow over the socket and seals
> first and then go to the anode.
>
> 73, Bill W6WRT
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