Hi John,
I used to be on 23 CM EME with a 5M (15 feet) homemade
dish. I used 4 of the N6CA amps in parallel, using 3 hybrids.
The watercooling jackets I used, was made of a piece of copper
tube that fit "almost" inside the tube. On the top of the copper
tube, I place a round piece of coppersheet. The coppersheet was
soldered to the top of the tube. In the copper sheet, I drilled
two holes, and soldered 2 small pieces of coppertube in these holes.
The hole thing was then put "into" the 7289's and glued with some
two component epoxy. I never had any failures with this approch,
ie no water leakage etc ! I have also used the "screw on" type of
jackets, but found that this approch was much easier to fabricate.
Carsten Groen, OZ9AAR
http://www.magicio.com/cgroen
> -----Original Message-----
> From: owner-amps@contesting.com [mailto:owner-amps@contesting.com]On
> Behalf Of John Fielding
> Sent: 12. maj 1999 18:36
> To: amps@contesting.com
> Subject: [AMPS] 7289's and other uWave tubes
>
>
>
> Hi all - a slightly off-topic question.
>
> I am updating my 23cm station for eme and converting the various
> tubes to water cooling.
> A question regarding the thread which is used to attach the
> air-finned cooler to the
> tube anode.
>
> In Chip Angle's N6CA article for a water cooled 7289 amplifier he
> states that the
> thread is 3/8"x16 which I assumed (incorrectly) was UNC. However
> when I measured the
> several tubes I had stripped the thread appears to be BSW
> (Whitworth). Can someone
> confirm this before I spend my hard earned cash on an expensive
> tap and die?
>
> BTW Several of the tubes I have are made by Siemens which use 2
> different thread forms,
> one is similar to the USA style but appears to be 12mm but a
> finer pitch than standard.
> The other type uses an inverse thread, the cooler is threaded on
> the outer part unlike
> the normal types which are threaded internally. Anyone care to
> comment what these
> threads might be?
>
> I have also designed a water cooling jacket for the Russian GI7bt
> triode which bolts on
> in place of the air-finned cooler. If anyone is interested I
> will send details on
> request.
>
> Thanks in anticipation.
>
> John ZS5JF
>
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