QRM on 2m - can you identify this?

[VK1JA]

An update...

After a bit of study and Google Zen, the closest mode that the QRM resembles is MFSK-11, Multi Frequency Shift Keying. We've tried DI-Fldigi to decode it but with no luck.

It generally starts at 5-6pm and runs through to 10.30pm (ish). The big news is that we're 99% certain it's coming from the couple next door. The tones stopped and we noticed that about 2mins later their lounge room lights went off and I'm guessing they went to bed.

So, what would be in a lounge room that would be communicating to another device via MFSK (or the like) that would cause this much QRM from 142Mhz to 147Mhz, every 10-12Khz? Get your thinking caps on guys !!!

One thing I thought of is that I've seen some TV's and AMPS (home theatre amps) can communicate to each other via an HDMI or normal audio cable. But surely it could be that strong and dirty to cause that much QRM through the 2m band..... My station isn't that sensitive !!

And then the next question is, how do we fix it.... It'll need to be something that can be plugged in, like a mains filter, plug in filter on the antenna socket (if that's where the QRM is radiating from)...

Thoughts?

[VK4TI]

An update...

After a bit of study and Google Zen, the closest mode that the QRM resembles is MFSK-11, Multi Frequency Shift Keying. We've tried DI-Fldigi to decode it but with no luck.

It generally starts at 5-6pm and runs through to 10.30pm (ish). The big news is that we're 99% certain it's coming from the couple next door. The tones stopped and we noticed that about 2mins later their lounge room lights went off and I'm guessing they went to bed.

So, what would be in a lounge room that would be communicating to another device via MFSK (or the like) that would cause this much QRM from 142Mhz to 147Mhz, every 10-12Khz? Get your thinking caps on guys !!!

One thing I thought of is that I've seen some TV's and AMPS (home theatre amps) can communicate to each other via an HDMI or normal audio cable. But surely it could be that strong and dirty to cause that much QRM through the 2m band..... My station isn't that sensitive !!

And then the next question is, how do we fix it.... It'll need to be something that can be plugged in, like a mains filter, plug in filter on the antenna socket (if that's where the QRM is radiating from)...

Thoughts?

I think you said they were approachable , so ask and explain , simply switching things of individually will find it then it's possible to fix after all guessing wont really help ?
obviously if they were unwilling to help acma would assist surely ?

[VK4WDM]

I agree with Barry It may only be some crappy cheap gear that can easily be replaced or the QRM fixed with a some ferrite beads and/or a shielded box. If it is something more serious than that then they need to know about it because it might be causing QRM on other frequencies as well and that could bring the ACMA to their door anyway.

73

Wayne VK4WDM

[VK3DXE]

Once you identify the culprit, try clip-on ferrites on all leads, as close to the quipment as possible. I've found them to be very good at reducing unwanted noise.

[VK1JA]

G'day Guys,

That's the path it looks like I'll be going down. Next time we cross paths I'll mention the QRM and ask if I can pop over and try and locate the offending device, armed with a handfull of clip on ferrites.

Hopefully that will at least reduce the QRM.

I'll keep the updates coming as I find info. If I do manage to get over and locate the device, I'll let you know what it is, model etc... It could help soemone in the future !

[VK3ZAZ]

Suggestions
most likely
Digital TV set
Set top box
Tablet
Pointless guessing, if they are approachable approach them
If not I doubt if ACMA can stop some electronic box that's not a transmitter interfering with ham band.
As for interfering with something else like emergency or aircraft whatever, unlikely, you can try that tack but wont be taken seriously
Its a hobby and you are not an essential service.
So go knock on door tell them you play radio and would like to find out what it is.

I told you how I got blamed for TVI and it was a plug pack in power point turning on every night for fish tank.
Went over and with some patience proved it was not me.
You have reverse if it is something they use every night hope you get to stick ferrite beads all over it.
it will be a test of human relations and just cos you are a ham gives you no rights.
BUT if you mess with their electronics and something goes wrong they WILL blame you so take due care before you start messing with their electrical appliances.

The fact 2M is primary does not obligate neighbors not to own some device that causes problems,
unlike FCC who seem to be able to stop things ACMA don't do that sort of stuff very much and if you call them you will probably have to pay them.


2 cents

[VK2GOM]

...I doubt if ACMA can stop some electronic box that's not a transmitter interfering with ham band.

Absolutely they can. I saw them issue a blue non-compliance notice for a switched mode 22V power supply once that was causing havoc on (secondary allocation) HF bands. The fact it was in my own attic (but not mine - I live in a rental gaff), it was pointless forwarding the blue notice on to the rental agency and be seen as a troublemaker. I just replaced the PSU out of my own pocket.

They should be even more eager for interference to a primary band used by a customer.

But the ACMA did come out to investigate.

73 - Rob VK2GOM / GW0MOH