On 12/17/2019 9:07 PM, Kim Elmore wrote:
I think Ed (W1RFI) has cautioned us that the FCC long ago decided not to address
radiated emissions below 30 MHz and that they are unlikely to do so in the future. As
far as they’re concerned, the HF issue has sailed.
What it boils down to is that
1) Rules were adopted many years ago, with the usual influence from big
2) Rules were based on the assumption that nothing exists other than the
power line for conducted RF.
3) Test setups are specified in such a manner that fundamental design
and construction errors as important and as common as "The Pin One
Problem" are never seen or excited. This includes the all too common
failure of a "Pin One Like" problem with termination of the Green Wire,
and of coax connectors in CATV systems and home entertainment equipment.
And it is #3 that is, by far, the most common and most powerful
mechanism for coupling RFI in and out of equipment. It is, for example,
the most likely mechanism coupling HF backhaul data in CATV and DSL
systems (see page 2 of http://k9yc.com/KillingReceiveNoise.pdf and note
the link to work by W0QE and W0IVJ to document it). This stuff is almost
certainly common mode current on coax shields, coupled by Pin One
Problems at the point of connection, and coupled by I/O circuitry in DSL
systems with poor common mode isolation.
73, Jim K9YC
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