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On initial listening it sounded like it could be a power line issue causing an arc - but the more I listened you can clearly hear it is data of some type, possibly TDMA data or similar due to the "buzz" in AM Mode, with the regular and often similar signal? Observing this signal on a spectrum analyzer may help you narrow down the source as you are likely seeing an image/mix/harmonic from a data transmitter.? It could be any number of things - from a cell phone or cell site to wifi, smarthome devices, or utility smart metering.? We had a similar issue that went on for weeks a few years back that not only intermittently?caused interference on VHF but also drifted up and down the VHF band including into public safety spectrum.? I successfully located the source of that interference after a few weeks which was the transmitter for a J-Tech paging system - the same as those used in many restaurants - located in the same-day-surgery waiting room of a local hospital.? The transmitter had a defect that was causing it to emit a spur in the VHF band and for some reason that spur would slowly drift up and down in frequency over time.? The transmitter was set for anti-walk-away mode which transmits a data signal at regular intervals - and if someone walks out of range with one of the pagers it sets the pager off, decreasing the chance of someone taking a pager or missing a page.? Hospital security powered down the device which confirmed it was the source and tagged it out of service until it could be replaced/repaired.

If possible I would recommend that you observe the signal with a spectrum analyzer as this will likely help you pinpoint the center frequency of the interference source, which is likely a much higher level than what you are observing.? If the noise is broad-band this method will also confirm that.? Keep in mind the selectivity of the receiver you are utilizing in these videos is quite broad and as such the signal may be perceived to be broadband when it may not, in fact, be so.? Your input frequency is also extremely close to the upper band-edge of 2M so the chances of receiving interference from a device in the commercial/public safety range is elevated.? Another useful observation would be if you could capture the audio waveform so it can be visually compared to known modulation types.? This can be done using a service monitor oscilloscope mode or simply recording the audio and using an audio editing application to inspect the waveform.

Thanks,

Dan Woodie, CETsr

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