Interference to a local emergency services 450 MHz repeater has been noted in the form of “kerchunks” every 10 seconds for about 1/4 second. The source of the interference has been found from a trunked public transportation system. A malfunctioning LTR repeater transmitter on their tower gave broadband, highly illegal bursts of interference at high power.
I can audibly hear it across about 4.5 MHz bandwidth. I hear it as a distinct “click” in the SSB receiver anywhere in that band when this one specific transmitter that is over 5 kilometers away goes from inactive to active.
Note: it sounds like a “beat note” when two signals are beating together