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[AMPS] 6m amp

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Subject: [AMPS] 6m amp
From: (W7XU Arliss)
Date: Sun, 14 Feb 1999 08:47:44 +0000

I think the efficiency of my homebrew 6m 8877 amp is 
lower than it should be (currently about 50 %), and am
looking for some suggestions on how to improve the

The amp runs about 2800 V key down at 1 amp, with 50 mA
of grid current, into a 50 ohm load.  Idling current 
(set with a 12V Zener) is about 75 mA.  The plate 
circuit is a Pi-L network patterned after Lauren Libby's
(W0LD) HR article from July 1986, using a vacuum variable
tuning capacitor, 3/16" copper tubing for the coil, and
a 250 pF air variable for the loading coil.

I've tried varying the coil size somewhat but that hasn't
made any difference.  I also tried increasing the plate
voltage to 3500 V, which reduced the drive requirement, 
but didn't make a significant difference in the amp's
efficiency.  The coil is about 1.5" away from the cabinet

Other suggestions?

Thanks & 73,  Arliss  W7XU

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