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New to SW listening question: "Thump/Beat" sound

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kc8mln

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Howdy all, I am newly getting into shortwave listening and wanted to inquire about a question...

As I scroll through the band, I am hearing a "thump/beat" sound that comes and goes as I scroll the band, I'd compare it to the sound of a heart beat that gets stronger/weaker at certain areas across the band......can anyone help me with explaining what it is? Does it have to do with the heterodyne receiver or something else?
 
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ka3jjz

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It almost sounds like the AGC is pumping due to a strong signal slamming the front end. But first, what radio are you using? Mike
 

ka3jjz

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You mean an old Zenith?

And are you hearing this on the AM and FM bands, too?

If you're hearing it everywhere, it's undoubtedly a receiver fault of some kind. I'm not at all familiar with those old radios, but I suspect you would need to trace the signal backwards from the audio and RF stages to find the fault. I have a sneaky suspicion about leaky caps somewhere near or around the AGC or RF amp with a radio that old (wouldn't discount a nearly blown speaker, either. I've heard speakers that were about to go do things like that...).

Time to upgrade, I think...Mike
 

Boombox

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Does the noise occur on any other receiver you have? It could be some sort of local, electronic generated QRM.

For example, some cell phones can produce popping noises when placed within a few feet of a receiver.

Just an idea.
 

LtDoc

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The possible source of that 'thumb' is almost infinite. It can range from something in the receiver it's self, to something that's being emitted by something close to you, to a legitimate signal of some sort (that last one's a stretch, but still possible). All any of use can do is guess at it. If it's present over a very wide range of frequencies it's a fair bet that it's something either close to you or in the receiver it's self. Or... 'Momma Nature' just may not like you.
- 'Doc
 
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