[AMPS] Gi7B Tube Amps

[Johan Nordin]

>
>Peter Frenning, OZ1PIF wrote:
>>Ian et al.
>>
>>I'm running a single GI7bt (the ruggedized version) on 144MHz with 400W+ out
>>on SSB and running extensively WSJT (30s on 30s off 100% output) with 300W
>>out, using only an 18W muffin for cooling!
>>
>>No change to the anode cooler, and using the "flowerpot" trick for
>>concentrating the airflow.
>>
>>See my homepage for details....
>>
>>From: "Ian White, G3SEK" <G3SEK@ifwtech.com>
>>> However, I doubt that a muffin fan would be suitable for cooling any
>>> "external anode" tube unless you use *really* big fins with a minimal
>>> pressure drop. Muffin fans are very good for moving large volumes of air
>>> where there is no flow restriction, but they are not good at forcing air
>>> through the small gaps in a typical finned anode cooler. For that you
>>> need a centrifugal (squirrel-cage) blower.
>>>
>I was thinking about what's needed for low seal temperatures and long 
>life. Peter's experience only shows that his tube survives... but these 
>Russian tubes have very wide production variations. If the thermal 
>contact between the cooler and the anode was as poor as the one that 
>Traian describes, then it might need a lot more air. Fortunately the 
>tubes are cheap and extremely rugged, so if it breaks you try another 
>one.
>
>BTW, I remember some folklore that the Russian hams used to use GI7Bs 
>with vapour cooling. They had an open-topped pot of water screwed to the 
>anode, and a chimney in the top of the cabinet for the steam to escape. 
>They had to remember to pour in more water before it boiled dry... but 
>very carefully...

I have heard that story too, just check the water level now and then
to assure you donīt run the amplifier dry.
Good engineering practice? probably not but the plate will not reach higher temperatures than 100C  :-)
You will probably have to live with steamy windows in the hamschack ...

73īs de Johan SM3UZS




>
>-- 
>73 from Ian G3SEK          Editor, 'The VHF/UHF DX Book'
>                           'In Practice' columnist for RadCom (RSGB)
>                            http://www.ifwtech.com/g3sek
>
>--
>FAQ on WWW:               http://www.contesting.com/FAQ/amps
>Submissions:              amps@contesting.com
>Administrative requests:  amps-REQUEST@contesting.com
>Problems:                 owner-amps@contesting.com
>


--
FAQ on WWW:               http://www.contesting.com/FAQ/amps
Submissions:              amps@contesting.com
Administrative requests:  amps-REQUEST@contesting.com
Problems:                 owner-amps@contesting.com