|[AMRadio] GK500 OTA almost|
n4tua at aol.com
Fri Jan 6 13:31:58 EST 2017
I am reluctant to reinvent the wheel so to speak. It is working and making much RF. I will investigate a little better as I go with the scope and the watt meter.
I am not sure how to add neutralization to this rig.
The plate current moves up and down smoothly and equally as I rock the tune capacitor back and forth from resonance and the screen current peaks at resonance and and dips on either side. Much unlike it was doing.
Good Day, Collin
> On Jan 6, 2017, at 12:46 PM, Rob Atkinson <ranchorobbo at gmail.com> wrote:
>> On Fri, Jan 6, 2017 at 6:06 AM, Jim Candela <jcandela at prodigy.net> wrote:
>> I am glad you made progress. Is it really fixed though? \
> agree with some of Jim's comments but if it looks like a duck, quacks
> like a duck, walks like a duck, it's a duck. IOW, the rig's problems
> are reportedly gone. In my book that means it got fixed.
> Don't get too anal looking for probs that don't exist, however, it's a
> good idea to check for neutralization by dipping the plate and seeing
> if the grid current peaks at the same time.
> A common misunderstanding regarding plate parasitic suppressors is
> that they stop oscillation. Actually they create an environment where
> they are simply not possible at all.
>> Think of this
>> like a regenerative receiver that was breaking into oscillation. What you
>> did could have been similar to turning the regen knob CCW till it wasn't
>> oscillating. But is there enough regeneration left that might make the GK
>> 500 final unstable under various tuning conditions and then under
>> What I and others said still might need to be considered. Look at plate
>> dip, screen peak, and maximum RF output. If they do not ALL occur at the
>> same point, then the PA stage might take off under certain conditions, kind
>> of like a dog seeing the tip of his tail, and deciding to go for it, round
>> and round.
>> Others have mentioned neutralization. This would be ideal, but WRL and
>> Leo made a trade off to NOT do that. Doing so now might be a bigger project
>> than what you want to take on.
> that occurred to me also. You might be into modifying the grid input
> to get the capacitor back to the grid out of phase. But I don't know
> anything about the GK tetrode rig so I'm out of my area.
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