AM-radio with unstable frequency?

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JEL
Posts: 178
Joined: Wed Feb 07, 2018 2:08 am

AM-radio with unstable frequency?

Post by JEL » Tue Feb 25, 2020 1:43 pm

What might be causing this 'bouncy-house' signal?

I am guessing it is a Chinese AM-radio-station, but it is too faint for me to be sure.

The carrier kept going up and down several kHz like it was on a roller-coaster, but the signal itself was clear (Apart from being faint of course. What I mean is; the music in the signal sounded normal enough. Just the carrier was wonky)

I have seen similar behavior when local gardening-machines drive by a local park.

When that happens a splatter of FM-radio (Same as wideband broadcast-FM) pops up on odd non-BCFM frequencies with unstable carriers.

They behave just as erratic as this one in the video, except being local.

I'm assuming the people in the machines listen to music on some, perhaps, wireless devices which then for some reason transmits local 'interference'. I don't really know though.

However, this signal is definitely not local, so can't be local interference.

Could it be an error on the transmitter's part? (Hardware fault of some kind)

Or is this a signal that gets bounced off of something that modifies it into this wobbly thing?

It is the first time I have seen anything like this on HF, so obviously curious about it :)

https://www.youtube.com/watch?v=HXLApGwWLUc

snn47
Posts: 223
Joined: Tue Dec 27, 2016 11:00 pm

Re: AM-radio with unstable frequency?

Post by snn47 » Wed Feb 26, 2020 5:56 am

It could just be receiver intermodulation. If you have a 10 or 20 dB attenuator insert it and see if you still receive the station.

JEL
Posts: 178
Joined: Wed Feb 07, 2018 2:08 am

Re: AM-radio with unstable frequency?

Post by JEL » Wed Feb 26, 2020 6:44 am

snn47 wrote:
Wed Feb 26, 2020 5:56 am
It could just be receiver intermodulation. If you have a 10 or 20 dB attenuator insert it and see if you still receive the station.
Thanks, but I really doubt it is intermodulation.

When I get those they never move around unless I scroll the frequency-window. And when I do that they always scroll in the opposite direction of the normal channels, which is an easy way to identify them. This one does not do any of those things but behaves like a regular channel except for the wobbly carrier.

I will try attenuating the antenna-input if I see it again though.

mindwiper
Posts: 5
Joined: Wed Feb 07, 2018 6:46 pm

Re: AM-radio with unstable frequency?

Post by mindwiper » Thu Feb 27, 2020 2:13 am

same date and signal
https://youtu.be/4oI95N7EOsE

JEL
Posts: 178
Joined: Wed Feb 07, 2018 2:08 am

Re: AM-radio with unstable frequency?

Post by JEL » Thu Feb 27, 2020 7:49 am

mindwiper wrote:
Thu Feb 27, 2020 2:13 am
same date and signal
https://youtu.be/4oI95N7EOsE
Very cool :)
Much better reception than I got.

May not be Chinese after all, but perhaps some pirate-station?

I have noticed Russian pirates near 3 MHz and their AM-carriers drift all over the place too, similar to this one.
And I also receive those at about the same strength as this signal, so perhaps :)

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