ORIGINAL MESSAGE:
On Sat, 18 Apr 2009 08:08:08 -0400, "ka1mwp" <ka1mwp@comcast.net>
wrote:
>
>Thanks. Let me know if I am explaining this correctly, I tend to run on
>LOL
REPLY:
It sounds ok so far. I have not used a GU-84b but I have used a
4CX1000A and they should be similar. With zero drive, the screen
current is a little negative. With increasing drive, the screen
current goes more negative at first, then as drive increases it
becomes less negative and becomes positive as full power is
approached. At full 1500 watts output, the screen current is about +25
mA. Tuning is simple - adjust the plate tune cap for max positive
screen current and adjust the load for max RF out. The point of max RF
out also coincides with the +25 mA point, so basically, I just adjust
the tune cap for a screen current peak and adjust the load cap to make
the peak +25 MA. Once you know the values for your particular amp, you
can do the tuning without even having a power output meter.
Piece of cake.
73, Bill W6WRT
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