[Elecraft] Elecraft RF Probe

[Ron D'Eau Claire]

As you make the RF probe better able to handle high RF voltages you will
also cause it to be less accurate at lower RF voltages.

The common RF probe diodes have a turn-on voltage of about 0.2 volts. Below
that, they are almost open circuits and have no output. Higher PRV diodes
have turn-on voltages of closer  to 0.6 volts - three times that of the more
sensitive diodes. So it takes three times the RF voltage to even begin to
show a DC output and you'll need to be well above the turn on voltage to
show an output that accurately indicates the RF applied. Put two or three
diodes in series and you'll need 1.2 to nearly 2 volts  to just start
showing some indication of an output.

Bottom line, don't try to use such a probe for low RF levels.  

Ron AC7AC