[AMPS] 6m amp

[Steve Thompson]

In message <36C68DB0.7BA49915@dtgnet.com>, W7XU Arliss <w7xu@dtgnet.com>
writes
>
>Hi,
>
>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
>situation.
>
>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
>lid.
>
>Other suggestions?
>
>Thanks & 73,  Arliss  W7XU

How are you measuring the output power?

Steve

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