Best Tube to eliminate RFI

Lloyd Walker makes a kit that includes metal wrap and ground wires to place around miniature tubes that eliminate RF and microphonics.

This of course, assuming the radio signal is being picked up by small signal tubes and not through your interconnects or electrical system.

If these are 9 pin miniature tubes, there are also military RF shields that slip over the tube. The best ones include heat sink design.

I have a Walker kit that I bought some time back that I might consider letting you try. It does appear to be quite a bit of work to install, probably the reason I have not experimented with it.

The slip on RF shields would be the easy experiment, and I believe that BWS tube services has these in stock.

Here is his link: http://www.bws-tube.com/

here's hoping that future radio broadcasts be limited to your tuner.

I have had tubes pick up RF in only one situation. However I suppose there must be some instances where it happens or the military would not have manufactured RF shields in such great numbers.

In any case, the shields I purchased were about $5.00 each, and helped to damp microphonics as well as pulling away heat. Pretty cheap experiment for Keithcady even if it fails.

Many suggestions posted here are valid and should be tried as well. Perhaps I misunderstood Keith, it sounded like he had tried various tubes, which improved the rejection of the RF.

When the solution is found I hope the results are posted. Good info for future reference what ever the source of the problem.

Bruce at BWS should still have the tube shields. If not, I may still have some around here that you could borrow.

The Walker kit is available from Loyd Walker, if not that too is here still in the original box.

You did not mention whether changing tubes had any effect on the RF. Also wonder if signal could come in from the power line. Shielded power cables won't help if the signal is carried along with the AC.

Have you tried an extension cord running from another outlet? Would be interesting to see if that changed anything.

Ralph, certainly you know as much or more about tubes than anyone at this site. I know this personally from speaking to you on the phone many times. I believe you when you say a tube cannot pick up RF, I had this occur only one time and certainly it could have been something else (grounding, interconnect, etc..) that was causing the problem.

The one curiosity is why did the military manufacture so many RF shields for small signal tubes?