Reg Edwards wrote:
Owen,
I gather you are interested in measurents only in the 40m band which
makes life easier. The photograph of the loop and line makes it more
clear what you are up to.

Not necessarily, but the exploration of the loop has been done on lower
HF, and it happens that the BPL system that I have available for
measurement radiates on 7 and 10MHz in low HF.

7MHz is not the only band affected, these guys will use every scratch of
spectrum and power to maximise the speed / reach profile of their service.

....

Your calculations take the loop/line mismatch loss into account. Its
only a few dB.

Incidentally, have you considered what effects increasing the number
of turns to 2 or 3 would have? They MIGHT possibly be beneficial. It
needs more calculations. As with just increasing the size of the loop
which almost certainly would be beneficial.


I did.

It obviously increases the open circuit voltage. It also increases the
loop inductance, and this almost completely offsets the increased open
circuit voltage in terms of power delivered to the receiver input
depending on frequency). Calculation of the wire loss resistance becomes
more complex due to proximity effect, but that doesn't matter too much
because the dominant factor in determining the source Z is the
inductance of the loop, and even if tuned, the resistance is small wrt
the load.

Ofcom had the answer to measurements down to ambient noise level, the
antenna is shown in their recent reports on BPL radiation measurements.
However, it isn't a very portable answer.

As I said in an earlier post, an active loop and a portable short dipole
(such as the Buddipole) are avenues for investigation.

(A tuned loop obviously helps, but with the single frequency /
calibration issues.)

You have set yourself a most interesting and useful task. I wish you
well with it.

Thanks Reg, and I appreciate your help with the task in this discussion
/ review. Wish Amateur Radio well with it, because BPL is the greatest
risk to HF Amateur Radio that we have known. I don't say that from
having read or heard somone else's reports, I have stood on the streets
where BPL is deployed and measured it.

Though my measurement methodology has progressed from "calibrated
S-meter" readings, the calibrated S-meter is a reality check, and when I
last visited the trial site, set the receiver up and waved the 0.5m sq
loop (~-50dBi) about to see if they were still "on air", S-meter
readings of 5uV says they are, and it is seriously high in level.

Ofcom's recent reports are a great read, and it looks like they are
taking a sane approach at this point, differently to the fervour for BPL
expressed by Powell when at the FCC.

I better stop at that, I am getting OT!

Owen