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

[Gary Schafer]

Roger, if you have a Pi tuned input it is not easy to neutralize. Your feed
back (from the neutralization capacitor) needs to be out of phase with the
grid. You could connect it to the input side of the Pi network but probably
a better way is to put a small link around the Pi coil to connect to the
neutralization cap.

A simpler way would be to use a parallel tuned input circuit with a link to
the coax input connector. Then you can make it into a bridge neutralization
circuit where the bottom of the coil is above ground by a small capacitor at
which point the neutralization cap Is connected.

73
Gary  K4FMX

> -----Original Message-----
> From: Amps [mailto:amps-bounces at contesting.com] On Behalf Of Roger
> Sent: Sunday, July 26, 2015 7:51 PM
> To: donroden at hiwaay.net
> Cc: amps at contesting.com
> Subject: Re: [Amps] Follow-up...re: Time to ask for help.
> 
> 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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