[Amps] Follow-up...re: Time to ask for help.

[Vic Rosenthal 4X6GP/K2VCO]

You don't bypass the neutralizing cap. You reduce the value of the 
bypass cap at the cold end (away from the grid) of the grid tank circuit 
so that it will above ground for RF to some extent. You connect one end 
of the neutralizing capacitor to that point, the other end to the plate. 
This provides out-of-phase RF feedback. The ratio between the 'bypass' 
capacitor and the neutralizing capacitor determines the amount of feedback.

You need to look at the ARRL or Bill Orr handbooks. There are circuit 
diagrams that make this clear. It's called 'bridge neutralization'.

73,
Vic, 4X6GP/K2VCO
Rehovot, Israel
http://www.qsl.net/k2vco/

On 27 Jul 2015 03:50, Roger wrote:
> Sorry, I thought it was clear what I was trying to do. I have four 4x150a
> tetrodes in parallel, attempting to make them operate on 50mhz. I'm
> confident my DC is stable. Additional information includes, a Pi tuned
> input and output. Input and output terminations are quality 50 ohm devices.
> Power supply and rf deck are in separate boxes. My problem appears to be
> related to instability possibly caused by insufficient or incorrect
> neutralization.
>
> It was mentioned that the neutralizing cap needed to be by-passed and
> that's something I have not even considered. By-passing anything in the
> grid circuit seems contradictory to me.
>
>
> 73, Roger
> AI7RR
>
> On Sun, Jul 26, 2015 at 3:56 PM, <donroden at hiwaay.net> wrote:
>
>> Quoting Ron Youvan <ka4inm at gmail.com>:
>>
>>
>>>   I am trying to find out what you are trying to do.
>>>>
>>>
>> Me Too Ron,
>>
>> He has to make the amp DC stable before hooking up the input and output RF
>> networks.  We don't know if that's the case yet.
>>
>> Don W4DNR
>>
>>
>>
>>
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