If you find yourself short of sensitivity, try a tuned loop in the
style of a magloop and match the antenna to the receiver.

But whatever you adopt, accuracy will be limited by the uncertainty in
the amateur's receiver input impedance. This will change from band to
band and its actual value will be a matter of guesswork.

A receiver's input impedance can be masked with an attenuator. But
this further reduces sensitivity.

With amateur grade equipment, facilities and environment, expect a
measuring uncertainty in the region of 4 to 7 dB at 7 MHz. Which is
good enough for most amateur purposes and makes your precision
calculations, including conductor diameter and conductivity, not worth
the trouble.

All you need for calculation is enclosed loop area, loop inductance,
receiver impedance and a pocket calculator.

The uncertainty of a measurement is just as important as the value
itself. The only way to assess uncertainty is to compare with
professional-grade equipment. In which case, if professional grade is
obtainable, you can dump the amateur stuff.

I do like the way your calculations appeared on my screen with one
mouse click.
How do you do it?

----
Reg.

==================================

"Owen" wrote in message
...

I have been working on the BPL Interference issue.

One of my projects has been exploring ways by which ordinary (well,
competent anyway,) amateurs can make reasonably reliable
measurements of
noise / interference using existing amateur station equipment or
equipment that is easy for amateurs to construct.

This has led me to search for a portable antenna of reasonably
predictable gain that can be used with a known HF SSB receiver.

I have had a hack at predicting the gain and antenna factor of a
small
square untuned loop driving a 50 ohm load. The model is in a Mathcad
worksheet, but I have copied it to a gif file which you can view on
my
website at http://www.vk1od.net/bpl/loop.mcd.gif . (The worksheet is
entirely in metric units.)

I would appreciate any comments / review on the model and calcs.

Owen