[Moon-net] Gain of a tetrode (TH347) - corrected

Mon Oct 1 12:48:05 CDT 2007

Guenter
The TH347 takes max 250W drive on 23cm in linear mode. Make sure that the G2
current is not limited below 70mA. The Bias current is set at 50mA as yours.
I feed 250W, have 60mA G2 current, UA is 3340V, 2A.
Be careful with heater voltage. Backheating on 23cm is substantial in this
environment and cathode needs power blower to remain calm.
Air exhaust at plate must not exceed 75C.
73
HB9BBD Dominique

-----Ursprüngliche Nachricht-----
Von: moon-net-bounces at list-serv.davidv.net
[mailto:moon-net-bounces at list-serv.davidv.net] Im Auftrag von
Koellner,Guenter (NSN - DE/Germany - MiniMD)
Gesendet: Montag, 1. Oktober 2007 20:31
An: moon-net-bounces at list-serv.davidv.net; moonbounceboard
Betreff: [Moon-net] Gain of a tetrode (TH347) - corrected

Hello,

back to a technical question:

On 23cm, my amp is using a TH347. I have about 75W drive (from a GSM
amplifier) and am getting about 950W output from it. While tuning and
optimizing, I found that the gain increases when I am increasing the idle
current, so this situation is at 300mA idle current.

I am now going to get more drive power, the plate current might become too
high and the plate loss too much. In order to compensate here, I may reduce
the idle current. But, how much less gain may I get when I for example
reduce idle to 50mA. Not that I now drive it with 3dB more and on the other
hand loose 3dB of gain, so that at the end the output is equal.

73, Günter (dl4mea)

corrected: was 300mA drive power -> 300mA idle current

_______________________________________________
Moon-Net posting and subscription instructions are at
http://www.nlsa.com/nets/moon-net-help.html