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Old December 29th 08, 08:05 PM posted to rec.radio.amateur.homebrew
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Posts: 317
Default RF probe for millivolts?

In article
,
K7ITM wrote:

To be sure I'm not trying to blow smoke some bad place, I just tried
this, with a 1N4148 as detector.


Tom & Larry-

Perhaps it is understood but not mentioned. If a test point has a DC
level, connecting a diode might disturb the circuit.

If an oscilloscope is not available, I would use a 0.001 MFD series
capacitor from the circuit, to a 10K Ohm resistor shunted by a 1N4148
diode to ground. The junction of the capacitor and diode/resistor
combination, becomes a new test point that can be read on the lower
ranges of a DC multimeter.

Of course the reading is only relative, but is quite handy when you need
to tune for maximum output. In some cases I've permanently wired these
test points into the circuit. That way you don't change tuning by
removing the circuit.

Fred
K4DII
 
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