Ed Price wrote:
Looks pretty decent, until the very end. Antenna Factor (AF) is the ratio of
the field strength voltage to the output VOLTAGE, not power, although you
did get the numbers right.
I have looked at it and I can't see that I said "power" in relation to
Antenna Factor. Perhaps I am blind. (You didn't confuse the units dB/m
(dB per meter) with dBm (db wrt 1mW) did you?)
So practically, since the average ham has a receiver with a sensitivity in
the order of a microvolt, then your antenna limits your minimum discernable
signal level to around 65 uV/m. Maybe 100 uV/m to be on the safe side.
In fact, the technique calls for measuring signals on the rx from the
noise floor to about 20dB above it. The noise floor for receivers today
is typically -135dBm.
That's likely quite adequate for detecting BPL noise, but the real problem
is having the average ham get an anywhere near reasonably accurate
measurement of 100 uV. Your S meter just isn't good enough, so now you're
moving beyond the "average" ham's capability. Accurizing your receiver into
an RF microvoltmeter is a tough task, so maybe the best route is to use a
signal generator as a comparison standard. Old boatanchor signal generators
in the 7 MHz region are reasonably available, and their attenuators are a
lot better than their frequency stability and portability. g
No, the technique does not use an S-meter. In a nutshell, it uses Ed
Hare's (W1RFI) technique for calibrating the noise floor of the
receiver, using an external attenuator to keep the rx input below the
AGC threshold, and measuring the audio output with signal and the audio
output from rx internal noise as inputs to a calculation of the input
signal power. Applying external attenuator losses, feedline losses and
antenna factor allows calculation of field strength.
I applaud your goals, but getting data accurate enough to toss into an
intelligent argument about BPL is a tough task. Good luck.
I have gotten sidetracked here, my real interest is the completeness /
accuracy of the loop model.
Owen
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