[morzh]

Remind me again, why this happens?

When tuned the signal is nice, but between stations it is buzzing.
Not much squealing, only a little and only in certain points. Mostly buzzing.

The effect is practically absent in my 20 or in 80jr.
It is the most pronounced in the 18 and also exists, though to a lesser degree, in my Zenith 9S262.

And as I said, when tuned, the sound is good.

At least in 18 I replaced the filtering caps from either line to the chassis with Y-caps, 10nF each.

Did not move much wires when recapping.

[BrendaAnnD]

Wish I could help you on this one, but I have that problem with ALL of my radios because of the noisy electrical grid here (fluorescent lights are nearly universal here).

[Radioroslyn]

And if you short the ANT to GND do you still hear it??
Terry

[BrendaAnnD]

On all but the deafest sets. I think it gets in through the line..

[morzh]

No, when I short them, it's all quiet.
And, as said before, when tuned in and the signal is strong, also no buzz there.

[jerryhawthorne]

Mortz, in your case sure sounds like something is radiating RF noise in your environment. Brenda sounds like she has something on the A/C line. But what do I know?

Jerry

[Radioroslyn]

Well unfortunately the RF environment isn't as good (clean) as it use to be. Using a coax feed ant may tend to help. Having a good earth gnd can't hurt. And a good long high up ant is a good thing to. Noise is everywhere!!! and it,s very annoying!!
GL w/it
Terry
ps A loop ant may be a good thing as you can use it to null out the noise as much as possible.

[morzh]

Good question is then, why the 18 with a hanging piece of wire is buzzing, whereas say my 20 (a TRF) also with a wire is not. Nor does 80.

....pollution...tell me about it! I have just come from a RF EMI sniffing session of my device, where I saw cell phone signal getting into unechoic chamber....

[Mondial]

Probably the reason you hear the buzzing with the 18, but not the 20 or 80 junior is that the 18 has AVC while the 20 and 80 do not. When not tuned to a station, the 18 AVC line drops to 0 volts and the gain controlled stages are running flat out at maximum amplification. As soon as you tune to a station, the AVC voltage rises, reducing the gain and along with it the residual received RF noise level. The 20 and 80 with manual gain control do not automatically increase the amplification as you tune off a station, so the background noise level does not rise noticeably.

The 18 is also a much better receiver and has a lot more reserve gain than either the 20 or 80, so the off station background noise is more apparent than with the lower sensitivity sets.

[morzh]

Yes, and this may be the same reason for the Zenith 9S262, as I think it also has the AVC. In fact I know it does as the AVC runs the Magic Eye tube.
I need to listen to my Westinghouse, as it also has the eye and AVC. If it does the same then this is probably the culprit.

[GarySP]

Just a thought... have you tried running your set through a good surge protector? I had a problem with line noise with one of my televisions, and the surge protector cured it. Make sure it has pre-filtering in it. Can't hurt to try. Take care. Gary

[morzh]

Gary

It is not line noise. Line noise is always present. You can't tune it out really.
It sounds excellent when tuned.

Also I have Y-caps 10nF from both line and neutral to chassis.

One thing I did not try is connecting Ground. But I don't hold my breath on this one.