On Wed, 29 Jun 2005 01:04:59 -0400, Buck wrote:


I used to tune my Swan with one. I found when I used an SWR meter,
the minimum SWR dip was NEVER the maximum field strength reading. I
always had to raise the SWR to about 1.3:1 or so.

The probable reason for maximum power output not coinciding with the
plate current dip is imperfect neutralisation (whether or not the
stage is neutralised). If you have a neutralisation adjustment, you
can get the two to coincide by properly adjusting the neutralisation.

You can use this coincidence as a quite sensitive indication of
optimal neutralisation if you use a digital meter to monitor plate
current, and the power out indicator to monitor RF output power.
Adjust the tuning and loading for rated power into a dummy load, check
the tune cap is peaked for max Po, observe the plate current,
carefully dip the plate current, noting whether the dip was left or
right of max Po. Now tweak the neutralisation until the two coincide.

When it is all done properly, the "dip" of the plate current should be
symmetric, ie it should be as "sharp" approaching from one side as the
other. (Asymetric dips are another symptom of non-omptimal
neutralisation.

Owen
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