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

January 7th 04, 09:25 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 will not be able to see the output using a power meter when
disabling the plate and screen voltage. An rf voltmeter or scope will
work.

Do this on 10 meters.
The easiest way to neutralize the final is by leaving all voltages on.
Tune up as normal into a dummy load.
Now as you tune the plate tuning control watch to see if you get a dip
in the plate current at exactly the same point that you get a slight
peak in the screen current. You should also get maximum power out at
the exact same point.
If not the neutralization cap needs to be adjusted. Adjust in small
steps and retry for the above.

If the grid current goes up when you tune the plate tuning to the high
side of resonance the neutralizing capacitance is too small.

If the grid current goes up when you tune the plate tuning to the low
side of resonance the neutralizing capacitance is too large.

When you get done the grid current rise should be smooth with less
increase than before and at exactly the dip in plate current. Also the
power output should peak at the same point.

You may not be able to get it exact but it will be ok if you get close
to that.

When properly neutralized you may find that you have less apparent
grid drive available. This is because the feed back before was
enhancing the grid drive.

73
Gary K4FMX