[Elecraft] BPL achilles heel

[Stuart Rohre]

Some years ago I did EMC/RFI testing of power distribution transformers for
a Loran project station.  Many power transformers of the pole pig type have
a 20 dB loss to HF frequencies.

Those Loran power pigs had been made of dry windings, using tape core
techniques, and flat copper tape for winding conductors.  They had so much
capacitance that they resonated in the HF band where Loran operated and thus
could not isolate the power line from RF feedback from the transmitter site!
The contributing factor had been the potting of the phase windings.  To cut
down on epoxy needed, they added filler material that was ferrous rock!  A
real dandy loaded, tuned, circuit when they finished.  Naturally, they
failed the government spec.
-Stuart
K5KVH