Dear Gary, LF Group,
Using a 100u-0-100u meter should not be a problem. The phase detector
circuit has a full scale output of around +/-250mV, with a fairly low source
impedance - just select a series resistor R2 for your meter that will give a
full scale reading with 250mV DC applied. Shunting the meter movement should
work fine too, but it needs 1 more resistor. The exact calibration will vary
somewhat with the forward voltage of the particular diodes used, and the
applied power level. The calibration is not critical, however, since you are
really only looking for a zero reading anyway.
The meter is normally connected between the transmitter output, and the
feeder to the loading coil and matching transformer. A reasonably low
harmonic content at the TX output is needed for the phase meter to work
properly - but with the usual push-pull TX output and 2 section low-pass
filter, this should not be a problem.
Cheers, Jim Moritz
73 de M0BMU
----- Original Message -----
From: G4WGT - Gary <[email protected]>
To: <[email protected]>
Sent: Friday, February 27, 2004 6:29 PM
Subject: LF: RE: RE: RF Current meter
Hello Jim & LF Group,
The only query at
the moment is regarding the phase meter (1mA-0-1mA), if I were to use a
100uA-0-100uA meter with a shunt would this cause any problems with your
design or maybe increasing the value of R2 would be acceptable, (I have
this
meter already in my junk box), the 1mA meter for V & A metering is not a
problem.
Just had another thought, I presume that the device is to be inserted in
the
coax feed prior to the antenna matching arrangement at the antenna end.
73
Gary - G4WGT
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