RadioBanter - View Single Post - Neutralization tips for TX-1 Apache Needed

January 7th 04, 07:46 PM

On Wed, 07 Jan 2004 06:51:16 GMT, (Space
Charge) wrote:

The manual is rather sparse on this, and I was wondering if anyone out
there has any hints or kinks that will aid in neutralizing the Apache
TX-1 final stage. A brief description of the process would be great,
as the manual doesn't seem to directly address it.

Also, the previous owner seems to have doped (red colored) the final
ceramic tube sockets and the solder lugs, and capacitor leads; Good
idea? (The dope seems to be flaking/failing in some places.)

Thanks to the group,

Lin/KJ6EF
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You can't do it with a power meter with the hv disconnected. You would
need an rf voltmeter to see the output. Or a scope.

But the easiest way is to leave all voltages on. Tune up into a dummy
load to proper power. Then watch the grid current as you tune the
plate tuning of the final. Grid current should peak slightly at
exactly the dip in plate current. You should also get a peak in output
at the same point. If not adjust the neutralization cap slightly.
Do this on 10 meters.

An increase in grid current on low frequency side of plate resonance
indicates neutralizing cap is too big. An increase in grid current on
the high side of plate resonance indicates the neutralizing cap is too
small.

As you get closer to proper neutralization you will see less of a
change in grid current as you tune the plate through resonance and it
will be smooth.

You may not be able to get everything to exactly coincide but you
should get close.

73
Gary K4FMX