"Rick" wrote in
:

....
The photo on that web site is essentially what I built, except mine
was multiturn, and had no balun.

What you described is not IMHO a substitute for an effective balun, so
you can expect shallower nulls, and a distorted pattern (ie unequal nulls
and the nulls not orthogonal to the plane of the loop.

Although the power lines act as a very long antenna, I have had no
difficulty locating BPL injection points using the loop nulls. If you
stand under the power lines, you won't get a result, you need to move
away from them, preferably at least a quarter wave, and not near other
conductors (eg metal rainwater plumbing, other overhead metallic
services, metal fences, motor vehicles, buildings with sarked walls etc).
That is a big ask, but if you do that, and use the nulls, you should
readily get a good set (ie reliable, convenrgent) of cross bearings.

Sure you can look for interference at 70cm or at ultrasonic
frequencies... but that won't work unless the source is truly wideband.
The other thing is that if you make a complaint, demonstrate emissions at
70cm, and they fix them at 70cm, what do you do if they didn't solve your
primary problem. I have seen people do that, and the power company at
significant expense solved the reported problem, but not he complainants
real problem. Further complaints were treated as vexatious... 'quick as
we fix one problem, you find another'.

IMHO, better to measure the problem at the primary frequency, report the
real problem, not the cause, but the primary impact on yourself.
Depending on the jurisdiction, power companies may not be obligated to
eliminate the emission, merely to reduce it to comply with some standard,
and in that case, absolute measures of field strength may become
relevant.

Don't dismiss the loop and receiver, highly likely that if the regulator
attend to establish whether there is a case or not, they will *measure*
the emission field strength with a calibrated loop and receiver.

Owen