[AMPS] Stability Question

[Roy Koeppe]

-----Original Message-----
From: Roy Koeppe <royanjoy@ncn.net>
To: amps@contesting.com <amps@contesting.com>
Date: Sunday, February 07, 1999 8:56 AM
Subject: Re: [AMPS] Stability Question


>Determine the oscillation freq. If it's VHF then perform all of the
>Measures' measures. (Pun intended).
>
>73,    K6XK
>-----Original Message-----
>From: Jon Ogden <jono@enteract.com>
>To: Amps Reflector <amps@contesting.com>
>Date: Saturday, February 06, 1999 7:40 PM
>Subject: [AMPS] Stability Question
>
>
>>
>>Quiz time!
>>
>>I am finally at the point in putting my amp back together where I can run
>>some stability tests.  And I have come up with a question/problem.
>>
>>Here's how I am testing:
>>
>>Key up amp, no RF, Ctune at min, Cload at max, open circuit on output
>>(ie: no antenna or dummy load - no coax attached).  I figured this would
>>be worst case.
>>
>>What happens is I seems to have a housing based resonance problem with
>>one of my tubes.  When the cover is off, every thing is fine.  However,
>>when I put the cover on and bring Ctune close to its minimum value, the
>>plate current starts to rise.  I must have a resonance in the tank
>>circuit housing.
>>
>>I tried adding a 10 pF vacuum cap in parallel with Ctune as some have
>>suggested to improve stability in the past.  On paper you would think it
>>would work.  Effectively, you'd be raising the value of Ctune by 10 pF
>>and hopefully, it will never get low enough then to set the amp in to
>>oscillation.  Well, no such luck.  The amp still oscillates even with
>>this cap in place.
>>
>>So, what have you guys got for ideas?  Should I add some "walls" inside
>>the housing to try to break things up?
>>
>>BTW: My plate voltage is about 5.5 KV on the 4-1000A.
>>
>>Any help is appreciated.
>>
>>73,
>>
>>Jon
>>KE9NA
>>
>>
>>-------------------------------------
>>Jon Ogden
>>KE9NA
>>
>>http://www.qsl.net/ke9na    <--- CHECK IT OUT!  It's been updated!!!!!
>>
>>
>>"A life lived in fear is a life half lived."
>>
>>
>>--
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>>
>


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