[Amps] Neutralizing AL-1200

[Carl]

There is nothing elegant about that design, it was cobbled together.

You can feed in a signal generator with the amp turned off and use a 
receiver as the detector. Adjust for minimum feedthru after resonating the 
tank circuit as close as possible....use the manual settings.

There will be cover interaction so it will take time unless youre lucky.


----- Original Message ----- 
From: "Kevin K7ZS" <kevin.k7zs at gmail.com>
To: <amps at contesting.com>
Sent: Friday, March 02, 2012 10:44 AM
Subject: [Amps] Neutralizing AL-1200


> Hello List
>
> First experience with an AL-1200, received melted down filament wiring,
> which made a mess of the wiring harness etc.
>
> Had to disassemble the RF compartment, and foolishly did not record the
> position of the neutralizing capacitor, which is a small copper strap
> mounted to a standoff, and neutralizing capacitance is adjusted by the
> position of the strap with relation to the tube.
>
> I wonder if there is a way to adjust the capacitance with out constantly
> taking off the lid, adjusting it a tiny amount, closing the amp,
> powering the amp, and trying it again, and again, and again!
>
> At first it went into oscillation on 10 AND 15 meters, adjustments
> quickly tamed 15 meters, but 10 meters remains elusive.
>
> I have read of a way to adjust it by disabling the PA and measuring pass
> through power - but nothing in detail.
>
> Precious little out there on the web - so I can go through dozens of
> power cycles (poor tube!) or perhaps there is a way to position the
> 'neutralizing capacitor' in an more elegant, intelligent fashion?
>
> any help appreciated!
>
> 73 Kevin K7ZS
>
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