MURS interference

[Cheech]

Anyone else experience interference like this on the murs channels? This has been going on around here for years now. Used to be the channels were quiet and now this goes on for hours every day and night. At my house I pick this up on channels 1-3. I tried dialing up and down with the vfo on my radio and its only on the channels. Its not bleed over from something else.

I recently set up a mobile in my work van and have been monitoring while mobile. This past weekend I had to take a trip out of state to our camp in WV. My house is about an hour south of Cleveland Ohio. So I basically drove from one end of the state to the other. All along the drive I was getting this interference on one of the 5 channels. It changed channels at different locations.

All these years I thought this was something local to our area but its not. Someone has mentioned years ago thats it possibly from a paging system or something? Possible test beacon being used by someone like futronics? Anyone have any idea?

Here is a video from my house.

 

[brandon7861]

Garmin GPS dog collars. They use MURS to send short bursts of data to the receiver for the map feature. Sounds a lot like a telemetry RF pulse, but there is actually data in there. My driveway alarm uses MURS too, and I had to set tones to keep the data out.

There is a forum out there that mentions the protocol they use, but I never got around to figuring it out. The furthest I got was seeing the data with my oscope on the antenna. Wish I got a screenshot. Sounds exactly the same though, just enough to open a squelch.

 

[Cheech]

Garmin GPS dog collars. They use MURS to send short bursts of data to the receiver for the map feature. Sounds a lot like a telemetry RF pulse, but there is actually data in there. My driveway alarm uses MURS too, and I had to set tones to keep the data out.

There is a forum out there that mentions the protocol they use, but I never got around to figuring it out. The furthest I got was seeing the data with my oscope on the antenna. Wish I got a screenshot. Sounds exactly the same though, just enough to open a squelch.

Ive heard about the GPS thing when I was searching for what it could be. I think this might something else though because the signal strength is so strong at times. Its even strong enough to come in with other stations transmissions.

 

[brandon7861]

Those collars use decent antennas and the signals go a couple of miles. You might hear the signal get strong, then weak, maybe disappear, just to come back strong. That happens when the dog is moving in the woods. Sometimes they are laying down and the signal remains steady too.

Maybe it is something else, but the pulse frequency, duration, and sound it makes all match my neighbors dog collar. The sound is EXACTLY the same.

 

[Cheech]

This signal covers some serious ground. Ive left my house and driven 30 minutes away and have still picked it up. Thats why I can't see it being a dog collar. When I hear it on my base, my buddies that are around 10 miles away are also hearing it.

 

[brandon7861]

This signal covers some serious ground. Ive left my house and driven 30 minutes away and have still picked it up. Thats why I can't see it being a dog collar. When I hear it on my base, my buddies that are around 10 miles away are also hearing it.

Thats strange. There are companies selling data links for MURS. MURS can reach surprising distances so I wouldn't rule it out telemetry yet. Maybe someone is flying an rc plane or diy drone with a tracker. I read somewhere that the data links can cause squech breaking, but to me once a second say telemetry.

Take a few bearings with your HT from a few different places. Hold the handheld up close to your chest, antenna right against your body, and turn. When the signal disappears, your back is facing the transmitter. Repeat from a couple places, then go to where the lines would intersect and look for VHF antennas.

 

[Cheech]

I think the next nice day we get time we might try to track it down. There are a couple large tower sites where I think it might possibly be coming from.

I agree with being data or telemetry though.

I really think it might be futronics using it for testing purposes. I question the legality of that but it would explain hearing it across the state as they have multiple sites state wide.

 

[brandon7861]

Isn't Furtronics a medical company? I doubt they would use public license-free frequency for robots in the medical field, especially when medical devices have their own bands.

 

[Cheech]

Isn't Furtronics a medical company? I doubt they would use public license-free frequency for robots in the medical field, especially when medical devices have their own bands.

Welcome to futronics

futronics.us

 

[Cheech]

Here is another one while its going on all 3 151 channels.

 

[brandon7861]

Why would a big communications company be using public frequencies?

To stay within the law, the antennas cannot be higher than 60 feet, the power cannot be greater than 2 watts, and packet forwarding is not allowed. The use of public frequencies comes with the need to accept interference from other unlicensed users as well, not a good thing to build a service on.

Big companies that design complex microwave tower systems on one side of their shop are not playing with low powered MURS stuff on the other side. I just don't see that.

I now see it is also illegal to use MURS on an aircraft, so using it for drone tracking is not allowed either.

It makes for a good mystery to solve though, I'd love to hear what you find.

 

[Cheech]

Why would a big communications company be using public frequencies?

To stay within the law, the antennas cannot be higher than 60 feet, the power cannot be greater than 2 watts, and packet forwarding is not allowed. The use of public frequencies comes with the need to accept interference from other unlicensed users as well, not a good thing to build a service on.

Big companies that design complex microwave tower systems on one side of their shop are not playing with low powered MURS $#!^ on the other side. I just don't see that.

I now see it is also illegal to use MURS on an aircraft, so using it for drone tracking is not allowed either.

It makes for a good mystery to solve though, I'd love to hear what you find.

Someone had mentioned them causing interference years ago with their paging system and thats what sticks in my mind. It might not be them but with the range this is traveling it has to be coming from an actual tower site or so I would think.

 

[brandon7861]

Someone had mentioned them causing interference years ago with their paging system and thats what sticks in my mind. It might not be them but with the range this is traveling it has to be coming from an actual tower site or so I would think.

Definitely worth checking out. That second video also sounds exactly like the signals I used to receive. Sometimes it is strong and sometimes it disappears. If it is a dog, as he goes behind a hill or building, the signal will do that.

One thing that is clear is the period of the signal, and with the period being consistent, the disappearance and reappearance suggests signal strength variations. Would you get those variations from a tower site?

edit: At least it seems consistent. I can look when I get home loading the audio into a program

 

[Cheech]

The signal is pretty consistent. If I run a radio with a signal meter it will sit there and hit the same signal strength each time.

I also don't think its a dog collar because it goes on at all hours of the day all year long.

This has been going on for a long time too. The last time I had a mobile radio and was able to hear it while driving around was probably 2014.

 

[brandon7861]

Raveon sells MURS transmitters made for vehicles that can send, among other things, GPS tracking data to keep track of fleet vehicles. I imagine it would sound a lot like the dog trackers if used for just that purpose, but stronger.

Could a business in the area have these on their fleet vehicles?

VHF Data Radios | VHF Data Radio | VHF Radio Modem

www.raveon.com

They list a bunch of potential uses on their site