QRM on 2m - can you identify this?

[VK1JA]

G'day All,

For the last week or two I've been suffering from QRM on 2m. It spans most of the 144.100 to 144.500 segment, continuous running and just so happens to be quite strong (for weak signal work) right on the WSPR freq for 2m which I use a lot

It seems to be every 8-12Khz with varying strength within at least 142 to 147 range. It's not particularly strong, but it's enough to wipe out digital modes

I've uploaded a youtube clip where you can hear the tones and see what it looks like on Spectrum Lab.



http://youtu.be/WAe50Cb8G98

It's only when I point due south, and it seemed to start when the couple next door returned from a 2-3 year posting overseas. Saying that, I haven't walked to streets yet to find which house it's coming from.

If anyone has heard this QRM before, and can give a hint at the device that may be causing it it'll help me tremendously !!!

Cheers

Jayson

[VK2GOM]

It is obviously some sort of 'intelligent' device and not the usual PLI etc. that can plague 2m.

Whatever it is it needs dealing with, and the ACMA should assist if required, it being an incursion into a primary allocated amateur band.

It would certainly be worth a walk around with a handheld and any form of directional antenna to at least give you an idea of where its source is.

I know how frustrating interference can be. I've been there... many times!

Hope you get it sorted.

73 - Rob VK2GOM / GW0MOH

[VK1JA]

Thanks Rob, I might give ACMA a call on Monday and see what advice they can give.

My thoughts are the same, some sort of intelligent device with a very dirty output!!

I can't hear it on FM from my QTH, so I'm not sure how the handheld will go at tracking it down. It may be detectable when I get closer, failing that I'll do a temp setup with the TS-2000 in the car and go for a drive

[VK3HZ]

Hi Jayson,

Pure speculation here. It certainly sounds like a coded signal of some sort so it's probably an authorised transmission but on another frequency altogether. It's possibly a quite strong signal and you're just hearing spurii which may be being generated within your radio. So it may be that a simple notch filter on the Tx frequency is all that's required.

Do you have, or can you borrow a Spectrum Analyser to hook up to your antenna for a broader view of the spectrum? Failing that, it might be worth tuning over the full range of the TS-2000's Rx to see if there's anything identifiable.

Regards,
Dave
VK3HZ

[VK2OMD]

One of the problems that crops up from time to time is harmonics of ACTEWAGL's telemetry systems on 7xMhz, and I have heard similar sounds... but they are narrow band transmissions and it does not explain the repetition of the signals every 12kHz as a broadband emission.

Owen

[VK3BSF]

A weak broadband sig due south from a newly arrived overseas couple...Hmm...cud be a battery charger or other item on standby power..keep us in the loop

[VK3ZAZ]

G'day All,

For the last week or two I've been suffering from QRM on 2m. It spans most of the 144.100 to 144.500 segment, continuous running and just so happens to be quite strong (for weak signal work) right on the WSPR freq for 2m which I use a lot

It seems to be every 8-12Khz with varying strength within at least 142 to 147 range. It's not particularly strong, but it's enough to wipe out digital modes

I've uploaded a youtube clip where you can hear the tones and see what it looks like on Spectrum Lab.



http://youtu.be/WAe50Cb8G98

It's only when I point due south, and it seemed to start when the couple next door returned from a 2-3 year posting overseas. Saying that, I haven't walked to streets yet to find which house it's coming from.

If anyone has heard this QRM before, and can give a hint at the device that may be causing it it'll help me tremendously !!!

Cheers

Jayson

It will be some device or other.

PC TV Sm supply video game, infra red sensor, gate opener, or even a microwave clock.

And even if you find it if its not a prescribed or unauthorised device what can you do?

You have no power to go onto a property even acma needs prob cause.

On reverse I got accused of tvi which turned out to be s/w mode supply.
Welcome to real world.

[VK1JA]

Thanks for the replies guys, every little bit of info helps.

Update - 10.12am and the noise is gone, but for how long

Owen - an ACTEW device was one thing that came to mind. I have done a quick scan of the HF band but nothing unusual was found. Do you recall the freq in the 7Mhz band?

One my side I'd like to do a process of elimination before I start walking the streets to track it down. That'll mean going through and turning off everything to see if it's one of my devices that have a fault.

I do have a spec an (that was very kindly given to me from a local Amateur!!) but the input mixer diode is blown. But I do have a tv/sdr dongle that I can use as a spec an to see if it's internal to the TS-2000 or external. It may also be useful to walk the streets with rather than the TS-2000

I'm on good terms with my direct neighbors, and if it does turn out to be the couple that have recently returned from a posting, I'll talk them through the QRM, show them on the lap top etc. I'd be more than happy to help them find another solution to the device. One thing to remember is that who ever is using the device has no idea of what interference it's causing. They are just plugging it in and turning it on!

I'll keep you all updated.

[VK4GHZ]

Jayson, as a part of the process of elimination, can you borrow another multi-mode transceiver/receiver to have a listen with?
Tune the same range, same antenna, same...

(Obviously not another TS-2000, and preferably another brand)

Would rule out any TS-2000 internal mixing issues etc.

?

[VK1JA]

G'day Adam,

I'll certainly try to find another radio to use. I'm hoping the usb tv/sdr dongle will help in that regard. The tricky part will be hooking the usb dongle up to the yagi.... I may need to use a crude wiring to get it hooked up to the yagi.

[VK2OMD]

...

Owen - an ACTEW device was one thing that came to mind. I have done a quick scan of the HF band but nothing unusual was found. Do you recall the freq in the 7Mhz band?
...

I said 7xMHz, meaning 7x,xxxx,,, MHz... seventy something MHz, exactly half of where they are heard on 2m... but they are NW telementry transmitters, some in high spots like on water towers.

Owen

[VK1JA]

Ah, thanks Owen. I missed the x. I don't know if the TS-2000 will rx there, but I'll check. If not then the sdr dongle will for certain.

[VK3KGR]

Jayson,

Have a look at this site. You might be able to identify what it is.

http://www.sigidwiki.com/wiki/Signal_Id ... d=noscript

I found the link on the RTL dongle site.

73 Geoff VK4KJJ

[VK4WDM]

Hi Jayson

Are there any roadworks using portable message boards (Beware road works etc) or portable traffic lights around your area? I had a similar problem that started when roadworks started and went away when the road works were completed. Could not nail down a particular frequency but the signal they used was obviously causing cross modulation mixing products that were picked up by the receiver.

You have very good audio and visual evidence and I would certainly send it to the ACMA.

73

Wayne VK4WDM

[VK1JA]

Geoff and Wayne, thanks for the info and tips.

Geoff - I had a look through on the wiki site for unknown signal, I've booked marked the site (interesting stuff) but I couldn't find anything that was the same as the signal I'm getting. The closest thing I could find was a FSK signal, at least it gives me an idea though.

Wayne - no road works close by in that direction. But I'll keep that in mind!!

The interference seems to come and go throughout the day, and lines up with a device being switched off during working hours and then switched on when someone gets home in the early evening. It's goingto be a long road of investigations, and then walking the streets with a laptop/sdr dongle/yagi to pin point the source. Then to see if we can do anything about it....

Keep the ideas coming guys, it's all helping!

[VK2GOM]

I wonder if you could do a letterbox drop of a nicely worded letter, in plain language, that you suspect a device from a nearby house appears to be causing interference to a primary allocation amateur radio band? Give contact details in the letter to allow any neighbor to contact you directly if required. Advise in the letter that if the problem can't be solved locally, you will have no option but to have the ACMA investigate the cause of interference since the device is causing unlawful interference.

There is a small chance that this might bring the device in question into light before the ACMA have to come out with their DF gear.

73 - Rob VK2GOM / GW0MOH

[VK5PJ]

Hi Jayson,
rather than walk the streets, find a high or clear spot in the direction you think its coming from, go there and try to get a direction from there, if its now back towards your house you know its in your area and not some thing further afield.

Maybe some one you know has a small yagi that can be put on a car. I recall vk1do had a yagi on his utility at some stage (saw the video at Gipps tech some years ago).

The bottom section of 50MHz is now totally polluted at my place with a switch mode PSU wandering around the band, so this weekend its time to turn all of our electronics off and see if I can find the culprit.

regards,

[VK1JA]

G'day Rob and Peter,

Good idea about the letter box drop - shall keep that in mind.

Last night I remembered that I have a small 'cheap yagi' I could put in the car with the laptop/sdr dongle and do a bit of a scan around, that certainly would make it easier than walking around with a yagi and laptop !!!!

I have a feeling (and it's only a feeling) that it could be the couple next door that recently returned from the US, possibily with a new device that doesn't have Australian compliance, but I'll only know for sure when I do a site survey. In a way I hope it is them because I'm on good terms with them and we'll easily be able to work out a solution, unless it's a new US Tv that they have that's worth a squillian dollars..... Then I might leave it to teh ACMA to tell them they have to throw it out

I also rang the ACMA this morning and they seemed very interested. They have asked for further information, audio files, spec lab captures, freq, times etc which I'll supply. Ideally i'll be able to sort it without having to get the ACMA to come out, but time will tell.

Free time is hard to come by these days with being only a few weeks out from our wedding, lots of wedding plans to go through/check, but I'll see if I can get out on a weekend and do a site survey.

[VK2GOM]

A wedding shouldn't stop you Some years ago, I booked my motorcycle test (in the UK) and told my wife (to be) the date for it seemed familiar, but couldn't think why. I told her the date and she metaphorically smashed me over the head with a frying pan. I'd gone and booked it for our wedding day A quick phone call had it moved to the day after (the bike test that is, not the wedding).

That aside, back to interference fighting...

73 - Rob VK2GOM / GW0MOH

[VK1JA]

hahahaha, that would've went down well !

It must be a male thing, I'd be lost (and possibly dead) without my calendar reminders....