PA Tune Up Problems Why?? - Amplifiers Forum at eHam.net

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eHam.net Forum : Amplifiers : PA Tune Up Problems Why??

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PA Tune Up Problems Why??	Reply
by NU0P on December 24, 2004	Mail this to a friend!
My PA uses a pair of 6146B's and the loading control does not seem to work like it should. On any band it seems that he best power ouput appears to be with the Loading capacitor fully meshed like you might expect it to be on 80 but not on 20. After dipping the plate I would decrease the Loading cap a bit and watch the plate current rise and then re-dip the plate but the power out would decrease not increase. I can get reasonable power out on all the bands except for 10 Meters. Tubes are new. Any ideas why this would occur??? Steve NU0P

RE: PA Tune Up Problems Why??	Reply
by WB2WIK on December 25, 2004	Mail this to a friend!
What's the rig? Has it always done this, or is this new behavior for this rig? If it's new behavior, then something has obviously failed or changed; but if it's not, there's no reason to suspect a problem. WB2WIK/6

RE: PA Tune Up Problems Why??	Reply
by N0TONE on March 29, 2005	Mail this to a friend!
You have to be driving the grids pretty hard or you'll end up getting this result. With the LOAD cap fully meshed, the tuning condition should be max gain, but lowest saturated output power. If you're driving the tubes very gently, then max power will be at fully meshed LOAD cap - but it won't be much power. Drive the tubes harder, and then max power should occur with the LOAD cap more opened up - and it'll be higher power. AM

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