K7ITM wrote:
SNIP


Sensitivity for very low RF voltages is greatly enhanced by using a
high impedance meter. I would NOT put a 10k resistor to ground there
if I wanted sensitivity to low millivolt RF, since the diode average
current at low RF voltages is very low indeed. You can see that from
my reported results with the 1N4148 detector, with a 1 megohm meter
load versus with a 10 megohm meter load. With the high impedances
involved, the 100pF cap allows response down to well below what would
normally be considered RF frequencies. In the circuit described
above, the low-side 3dB corner frequency will be about that of the
100pF cap and the 10k resistor.

Cheers,
Tom

You might find this interesting:
http://www.cliftonlaboratories.com/d..._rf_probes.htm


Charlie.

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