Radio frequencies picked up by phono stage.

My cables and interconnects are boutique labels such as Black Cat which give great sound for the price and I am told they are shielded.

Some Black Cabels cables are not shielded if it’s not a dedicated PHONO cable. I owned several Black Cat interconnect cables and they are not good for phono signal, they are good as interconnect cables, but not for phono signal. Do you understand the difference between Phono cable and Interconnect cable? Change your cables if your model is the same as Black Cat Morpheus or similar models.

FWIW this could also be occurring at the output of the phono stage. I would at least try a different set of interconnects at the output of the phono section to see if that had any effect.

RFI can be really pesky. A phono section that picks it up can wind up being shipped back to the manufacturer for repairs, so usually some effort is made to prevent it happening. But not all designers work with the same tool kit! Several things affect RFI:

RFI injected at the input. RF beads can be installed to prevent RF getting to the input section if it makes it past the input connector. If the phono section is lacking 'stopping resistors' it can be prone to this sort of thing since the input device (tube or transistor) can then serve to rectify the RF, causing it to become audible. Stopping resistors can cause a Miller Effect high frequency rolloff, preventing RF from entering the gain stage. Don't worry if you don't understand what I've written, but if you send the unit back for repairs, point out this post to the manufacturer.

RFI introduced by poor grounding. This may be as simple as a bad power cord or a loose screw in the breaker box. Poor ground does include the grounding scheme of the equipment as well. 

The thing is, we're likely looking for something that has changed, since this problem suddenly showed up. For that reason I'm suspicious that the cause is outside of the audio system itself; IOW I think its a bad ground.

My cables and interconnects are boutique labels such as Black Cat which give great sound for the price and I am told they are shielded.

This is my old Black Cat Morpheus cables, they are not shielded!

They should NOT be used for a signal from a phono cartridge (no matter MC or MM) before the phono stage, they can be used as interconnect in analog chanin only after the phono stage.

You can get your FREE trial for Zu Audio Phono cables, try them and return them for full refund if you don't like them. At least you will be able to compare properly shielded cable to your Black Cat. 

I had radio pickup when I installed a Naim superline phonostage in place of a Michell iso, a known susceptibility of the superline, cartridge was a Dynavector 17D2 The obvious answer of just using the iso wasn't on as the superline was so much better in every other respect. Adding a 1nF to the 470Ω cartridge loading diminished the level to where it didn't intrude, 470pF was nearly as effective and preferable musically but no playing around with grounding various components made any difference, including changing the arm from my original Rega 300 with its rather odd grounding setup. Finally a change of rack to a largely non metalic one cured it, serendipitously as that wasn't why I changed it. I presume there was a focussing effect from the steel in the old rack, much as happens in a multi-element aerial.