[Lowfer] RF Ammeter recommendation

[John Andrews]

Ed,

> There's a pretty cheap way to go as well.  Use a (relatively) large
> capacitor as a shunt, with a smaller capacitor in series with a
> full-wave rectifier in parallel.  (Meter in the rectifier circuit, of
> course.)  Analogous to a DC shunt and meter.  Simple and works OK.
> Convenient for tuning and not bad for accuracy if you go to the trouble
> of analyzing the calibration.  Compared to a thermal ammeter has the
> advantage of a more or less linear scale.

I suspect that circuit would analyze out to be the same thing as the current
transformer, just done with capacitance instead of coupled inductors. Sounds
like a reasonable approach, assuming that the shunt cap can handle the
current, and that you don't try to remote the thing. As long as the meter
circuit is kept right at the antenna, it should be OK. Remote reading will
add some unwanted capacitance from the antenna to ground, depending on how
the wiring is run. I'd avoid sticking my finger in there while the rig is
running.

John A.