Roy Lewallen wrote in
:

....
The improvement noted by increasing the distance between the radiating
conductor and the consumer electronics (or power or other wiring
they're connected to) can be much greater than an "inverse square law"
would imply.

That's because a lot of the problems with interference occur in the
near field of the radiating conductor. In the far field, the field
strength is inversely proportional to the distance (the power density
follows the "inverse square law"). But in some parts of the near
field, the field strength varies as the inverse *cube* of the
distance. So even a small increase in distance can often have quite a
dramatic effect on interference level.

Roy,

The NTIA's long awaited second report on BPL has some interesting results
of NEC simulations to support the Part 15 distance extrapolation factor
of 40dB/decade on slant distance below 30MHz. NTIA have models at a range
of frequencies that explore the validity of the above factor, part II
which contains the graphs of the simulations makes an interesting read.

It seems to me that the issues to do with field strength vs distance are
quite applicable to a ham antenna as the radiator.

The report is at
http://www.ntia.doc.gov/osmhome/repo...7/bpl2007.html .

Owen