how to eliminate air-born RF

yes check your attic for a attic exhaust fan ours is quite noticeable if your near the wall where its mounted into. But killing the power to the entire house should turn its power supply off also? or possibly do you have any of those round attic vents they aren't powered by electricity they work through the heat rising it could need new bearings if you have any.

I am getting dit dat from a ham operater keying somewhere.  I just ordered some material that is supposed to shield from RF.  I have a
SOTA sapphire turntable and Hana low output moving coil on a unipivot  Ultracraft tonearm.  It is a function of where the cartridge is located above the turntable.  It is highest when not above the turntable platter but outboard of the record perimeter the noise  has some varation in volume and stereo channel it is on depending on the location over the turntable.  It does not disappear at high volume but is still apparent over mostly the outer edge of the platter but over the outer inch or two of record grooves.
I have tried different tonearm pipes(the tonearm has changable "pipes" not changable headshells), and tonearm bases.  It is present on a Hana low output moving coil and also on a moving magnet Grado mounted on a second tonearm pipe. Different tone arm cables make a minimal difference in the amount of the noise.   I even tried adding ferrite chokes over my tonearm cables 

Any thoughts?

The ONLY cure for RF (radio-frequency) interference is a Faraday cage; however, as others have mentioned, RF is hardly likely to be the culprit. Most likely, it is EM (electro-magnetic) interference rather than RF. As someone has mentioned, transformers related to other equipment are likely to contribute to audible 60Hz (and harmonics) noise. And, if your system is improperly grounded (or there are ground loops) it is extremely easy to have that noise induced into your signal. Likely culprits are the power supplies associate with low-voltage lighting (often halogen and/or LED), florescent lighting, door-bells, and some of the smart-home controllers that inject additional signal on top of the A/C line.

Given that most high-end gear-heads tend to spend ridiculous money on various interconnects, that is an unlikely problem. Some (poorly designed) preamps do not ground or terminate un-selected open inputs, creating a possible source of noise induction. Speaker cables, also, can pick up induced hum.

Cheap but VERY effective speaker cable formula:

1. Purchase a length of 2-conductor, 16 gauge, stranded copper lamp cord that is EIGHT (8) times as long as needed for your speaker cables.
2. Purchase terminators (spade lugs, banana plugs, whatever) appropriate for your amp and speakers.
3. Cut the lamp cord into SIX (6) pieces of equal length. They should be about 20-30% longer than you actually need to cover the span from amp to speaker.
4. Solder or clamp three of your new speaker cables to the terminators for the amplifier, making sure to observe polarity.
5. BRAID (like hair) the three cables together such that you get approximately one complete braiding cycle every four inches.
6. After braiding, solder or clamp the remaining ends to the terminators for you speakers, again, making sure to observe polarity and adjusting cable length to shorten if needed.

The reason for the 8X length versus only 6 pieces is that braiding shortens the effective length of the finished cable.

The resulting speaker cables can carry more current (and voltage) than even KW-rated amplifiers can produce. Moreover, they are as immune to induced signals as anything commercially available without going to shielded conduit. And, they cost relatively nothing. Win-win!

I hope it's not The Tell Tale Heart.
That didn't end up going too well for the first chap.

If I understand this correctly the hum still exists with the mains breaker is off = no power at all to the house. What we have here is a case of tinnitus.