Does anyone know what causes "whistling" or "screeching" in a radio receiver?

Gary

I have seen bad bypass caps and/or missimg tube sheilds cause this effect.
Greg

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:Does anyone know what causes "whistling" or "screeching" in a radio receiver?
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:Gary

The most common cause is listening to Yoko Ono.

Actualy your question has a lot of answers. everything in the RF section can cause this, dependion on how far out of whack it is. I bet Thomas can narrow it down if you can define it better. Like, on a strong station, between or approching stations. AM FM SW, What type of radio, hetro, nutro, superhetro, antenna?

I try. I'm no encyclopedia, though. Most of the info in my brain is from books, too, so I really can't take credit.

Aside from Yoko Ono, though, I'd have to say pretty much the same thing--condensers and shields. Condensers which filter B current in any way and in any size must be in good condition. Otherwise signals can pass through the B circuit and oscillate from one tube to another. Placing grid leads too close to plate leads can cause screetching. As I found out recently (from this web site and Norm Leal), triode tubes in a TRF can oscillate for no real reason at all except their own internal capacitance. Can't add too much more to what others say, though.

Ha! I found something else! You can also make a radio squeel by placing another one right next to it. They'd both have to be superheterodyes, though, or maybe one of them would have to be. Not sure if the other would have to be.

T.