[AMRadio] RE: Using a Ranger as a driver


John Coleman jc at pctechref.com
Wed Feb 13 11:01:40 EST 2008


As for a sweet spot on the loading of a rig I have never seen that.  But I
have always had 2-3 time the audio capability of what was needed.  I believe
in running a rig loaded to much less than the total audio that I have
available.  

One thing that is for sure, there is a sweet spot for loading on
tetrode/pentode finals because of the screen voltage on the RF final and how
it gets modulation.  This sweet spot has all to do with distortion where the
RF output needs to follow the modulation voltage as it is applied to the
final plate and screen.  This is best seen on trapezoid pattern display.
Adjust the screen voltage and screen modulation percentage with respect to
the plate modulation percentage while looking for straight edges on the trap
pattern.

On tetrode finals it is best to reduce the plate and screen voltage together
but it is really very seldom necessary.

John, WA5BXO



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