The following is copied from the VHF Reflector. The info on how to
measure the xfmr impedence was new to me; maybe others here also.
The original query was how much filter C was required.
73....Carl KM1H
Chris, depends on the impedance of your transformer and and filter
chokes... There's a chart in the ARRL handbook, power supply chapter
that shows the effects of various sizes of C for transformer voltage,
transformer impedance and load R (needs to include the bleeder R). If
your caps are paper then they have about the value labeled. If new
electrolytics they may be larger than labeled. If old electrolytics the
values may be smaller than labeled. Often in SSB power supplies the C is
made a bit (or bunch) larger to supply peaks better. If your transformer
is 1kv RMS you need lots of C to keep the output voltage to the 1.4kv
peak under load. But that power supply chart tells all.
You can measure the transformer Z by shorting the secondary, and then
bringing up the primary voltage with your variac until the primary
current is about the rated current. Then Z = applied voltage / primary
current... It should be in the range of 2 to 4% of the load R unless the
transformer is being used way outside its normal ratings.
73, Jerry, K0CQ
--------- End forwarded message ----------
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