How to eliminate FM RF coming thru turntable?

Are you using a tube or solid state phono stage?

I had similar problem and after trying many great tube phono stages, eliminated the trouble only by switching to ss phono stage. Cheers,
Spencer

Are you really sure that it is an FM station you are hearing? There are two things that seem to point to AM -- the fact that it is being demodulated into understandable audio, as discussed above; and the fact that the problem occurs only at night.

My suspicion would be that the day/night difference would be caused by differing signal strengths before/after sunset. As you probably realize, AM stations typically propagate much further at night than during the day. With FM, I believe that would only be true to a slight extent if at all.

If the other suggestions don't help, you might try this: There are kits that are available (I used to have one) that provide small value capacitors on rca plugs, for the purpose of optimizing the capacitive loading that is applied to the cartridge. Or you can solder up something like that yourself. If you were to add say 50 or 100pf of capacitance (connected at the preamp input with a y-connector), without going outside the range of total capacitance that the cartridge is specified for, the extra capacitance might load down the rf pickup sufficiently to kill it.

Also, you could try to find the kind of ferrite-based rfi filter that has a donut-hole in the center, through which the phono cable would be routed. That might do the trick as well. I think some of them are specifically marketed for audio applications.

Regards,
-- Al

Again, thanks for the suggestions. Makes no difference whether the lights in the house are on or off. For the renovation, the entire house was rewired. I have a dedicated circuit for the stereo. I tried plugging the equipment into different sockets on different circuits: made no difference to my problem. Did read that radio broadcasts are different at night, thus getting the signal when the signals are altered. It's the same FM station and begins around 5- 5.30 PM until after midnight. During the day, absolutely dead quiet. My phono stage is tube. Tried changing the tubes in case one or all were picking up the RF.

Some FM stations also broadcast on AM (or used to). Since demodulating FM by accident is virtually impossible something like this should be investigated. Many AM stations are required to REDUCE power at night because the signal travels so much further...to places where another station operates on the same frequency.

Are there any practical jokers near you?

I had a very similar problem also with a gyro se using a stock rb300 arm. In my case it was the tonearm cable picking up an am signal, I have no idea why but I was able to virtually eliminate it by reversing the phono inputs into the phono pre (plugging the left phono plug into the right input and right plug into left input) of course then I also had to reverse the leads from my phono pre to my linestage. Don't know if that's an option but it's easy to try.