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Sweeping Sound on Scanner Listening to Local Police Dispatch


Premium Subscriber
Jan 23, 2013
Palo Alto, CA
I've been monitoring my local police dispatch frequency for my city which is obviously on a repeater. Each time someone talks, whether it be a dispatcher on a base station or a police officer on their mobile/handheld, there is this constant "sweeping" like sound. Like the sound a broom would make. It's a constant sound that gradually fades in and then out like every second constantly for the duration of the transmission. Not sure if anyone's heard this before.
It occurs on multiple scanners that I own including a commercial-grade Motorola DMR radio.
Could it be some sort of interference or maybe even just the repeater that could be bad that's serving my scanners?

Extra Details:
It's on a VHF Frequency in the 158. MHz band on Analog.
They have 3 repeaters interconnected to cover more land as there would be dead spots if not.

--Let me know if I need to provide more details in addition to the above.
I can also provide an audio recording just so you get the idea of the sweeping sound if needed.


Premium Subscriber
Jan 23, 2001
Rensselaer, NY
If you are running multiple scanners, then it could be local oscillator emissions from one that is scanning nearby.