Guys...
I know in the Commander 2m single 3CX800 amps, the grid collets used had a
full complement of 'teeth'.
In other words, there were many contacts all around the collet.
Same deal for the K1FO (Lunar) 6m and 2m amps.
On the 70cm Lunar amp, some contacts had been removed to create a
'calibrated' amount of feedback.
Interesting thread.
73
Dick, K5AND
-----Original Message-----
From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of Gerald
Williamson via Amps
Sent: Monday, June 15, 2015 10:41
To: g8gsq72@gmail.com; amps@contesting.com
Subject: Re: [Amps] 3CX800 grid collet or SK1900
Hi Steve, you may well be right about grid inductance not being needed at
2m. It could be more for saving some costs.
This was the method used in the original Eimac published design by W6PO back
in the early 70's. The Eimac 8877 socket from that era and maybe still
today, used four grounding clips.
I have a 2m coaxial cavity amplifier that uses an 8877 with a continuous
fingerstock ring for grounding the grid. I never noticed it was in need of
neutralization so perhaps it simply does not matter which grid grounding
method is used on 2m and lower frequencies.
73,
Gerald K5GW
In a message dated 6/15/2015 10:18:39 A.M. Central Daylight Time,
g8gsq72@gmail.com writes:
The grid ring on a 3CX800 is the same size as the screen ring on a
4CX250 so you could dismantle a '250 base to get one.
I've done neutralising with grid fingers at UHF but not seen it needed at
2m.
Steve
> Hi Conrad, the four finger grid grounding may be there for the
> purpose
of
> neutralizing the plate to cathode feedback path.
>
> Sort of like you may have seen individual fingers removed from
fingerstock
> to create a small inductance from grid to ground.
>
> I have seen many 8877 2m amplifiers that use this technique.
>
> 73,
> Gerald K5GW
>
>
>
>
>
> In a message dated 6/15/2015 7:09:42 A.M. Central Daylight Time,
> g0ruz@g0ruz.com writes:
>
> I have a grounded grid 3CX800 2m amplifier that needs some TLC. One
> of
the
> most alarming things is that the grid is grounded by 4 small pieces
> of fingerstock that has seen better days. I thought that I would
> remedy
the
> situation and so I am looking for a grid collet or the SK1900 assembly.
I have
> just moved to the Netherlands and as yet have not learned where I
> can
buy
> suitable fingerstock that can be formed into a rig.
>
> Any help would be appreciated.
>
> 73
>
> Conrad PA5Y
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