Repeating Noise on GMRS 3 and 17 and 18

[WSAR863]

I recorded this repeating noise on these GMRS channels. 17 seems to bleed over to 18. Does anyone know what this is? It's constant and not my phone .

[OffRoaderX]

Where are you located? I've noticed this on Channel 17 for the last month or two, almost everywhere I go when I'm off-roading and at my house. This means I am hearing it over an area that is thousands of square miles of southern California - even when i'm deep in canyons where there is no line of site to anything. I am starting to think it is sunspots or aliens.

[WRYZ926]

It's definitely aliens. 

I'm interested to know more information too.

[WSAR863]

@OffRoaderX, you're the reason I started getting into radio. I hope I don't let you down! I'll try to keep my findings short... and to the point.  

I am North of Saint Martinville, Louisiana. I will drive around in the next couple days, use my yagi and see if I can figure out what it is. It has to either be very powerful (to penetrate canyons) or a satellite, right? My signal, on 18, appears to be coming from the direction of a cell tower, but I guess we'll find out. The one on channel 3 seems to come from everywhere, like your channel 18 signal. 

[Doggorunning1]

Well I thought we were talking about this guy, One thing I learned from the Greats like NotaRubicon is Rules matter! 

Below I made contact with the "X" Owner 

 

[WRYS709]

What transmitting tone do you have to use on Channel 5 to access that "simplex" repeater?

[SvenMarbles]

[Doggorunning1]

no tone, it grabs everything in the area 

[Lscott]

10 hours ago, WSAR863 said:

It has to either be very powerful (to penetrate canyons) or a satellite, right? My signal, on 18, appears to be coming from the direction of a cell tower, but I guess we'll find out. The one on channel 3 seems to come from everywhere, like your channel 18 signal.

What kind of radio is being used? If it's a cheap Chinese radio they're not known for good receivers.

Note that channel 3 is the Interstitial frequency, 462.6125, between the main channel 17, 462.6000, and main channel 18, 462.6250.

For GMRS the channel bandwidth is 25KHz so there is considerable overlap on channel 3 with the adjacent channels 17 and 18.  If the radio doesn't have extremely good selectivity you're likely to experience significant bleed over on 17 and 18 from a strong signal on channel 3.  Also a strong signal on either channel 17 or 18 will bleed over on channel 3.

FRS-GMRS Channels Layout.pdf

[OffRoaderX]

2 hours ago, Lscott said:

What kind of radio is being used?

I am hearing it with my Baofeng UV-5R, My Motorola XTS5000, and my XTL5000.

[tweiss3]

I wonder if it could be radar, though that should stop at 450, but you know, the feds do whatever they want.

Also could be a 2nd image of 925.225MHz, but neither would exactly explain the issue around both locations.

Edit: 925 is part of the LTE band. ATT did just have that huge problem last week. It is possible that their outage included firmware updates for the cell tower equipment and now something is out of band/creating an image.

[WRQC527]

Last night I checked in to a net transmitting from Santiago Peak in southern California. Net control is in Moreno Valley, 24 miles northeast of the repeater. Whenever net control was transmitting, and only when he was transmitting, an intermittent static crash, about once a second, would show up on his signal, actually disrupting his transmission. Some other folks checking in also had this same noise on their signal, but oddly, not everyone. It was either there or it wasn't. It seems like maybe the source was local to net control and others in his area, but not to people in other areas.  The Winsystem, an amateur radio linked system, has a large number of repeaters on VHF/UHF bands, and occasionally has to unlink some of their 440 repeaters because military radar signals get in to the repeaters. 

[Lscott]

1 hour ago, tweiss3 said:

I wonder if it could be radar, though that should stop at 450, but you know, the feds do whatever they want.

Also could be a 2nd image of 925.225MHz, but neither would exactly explain the issue around both locations.

Edit: 925 is part of the LTE band. ATT did just have that huge problem last week. It is possible that their outage included firmware updates for the cell tower equipment and now something is out of band/creating an image.

Could also be some mixing products in the radio's front end. Take a frequency on 931.6MHz (public safety frequency) and mix it with 469MHz (business frequency) you get the difference of 462.6MHz right in the GMRS range.

It could also be just the radio. My Kenwood dual band TH-G71A shows a full scale signal on channel 7. Take the antenna off, nothing. Then I tried several other radios on the same frequency. They show nothing there. So apparently it something weird with just the one radio.

[OffRoaderX]

5 minutes ago, Lscott said:

It could also be just the radio.

Then why does it occur on all my radios (forgot to mention in my list above it also happens KG-1000G+) and why did it just start happening a few months ago?

[WRYZ926]

2 minutes ago, OffRoaderX said:

Then why does it occur on all my radios (forgot to mention in my list above it also happens KG-1000G+) and why did it just start happening a few months ago?

Interesting. I'm curious to know what you all find out about this.

[OffRoaderX]

2 hours ago, tweiss3 said:

Also could be a 2nd image of 925.225MHz

I never thought of this.  I will check the other harmonics (above and below) for 462.6000 and see what I hear.

[WRQC527]

I actually translated the signal, it's a LifeAlert signal from the Moon. 

[SvenMarbles]

Do you think you can try to get more recordings of it, maybe for longer?

This sounds a lot like a data mode that isn't even in FM that's trying to be demodulated in FM.. If you do a lot of HF tuning, you'll know what I mean..

I wish i could be around for it and try to tune it on an RSP SDR.

 

 

[WRQW589]

Is there an MRI facility anywhere nearby?

 

In March, I went for an MRI. On my way to the facility my GMRS radio was on in the car, because I'm a boring person, like that.

 

When I got within three miles of the facility I started hearing buzzes, blips, and other strangeness on channel 17. I didn't think too much of it, until I was actually IN the MRI machine. Then I realized I was hearing the exact same sounds, the same buzzes, blips, and tones. It wasn't just similar, it was as if the GMRS radio was picking up the MRI machine's noises exactly as they sounded to me.

 

These things are supposed to be shielded, but apparently not well enough in some cases. After my MRI as I was driving home, I heard the exact same tones, until I got about three miles away from the hospital.

[WRYZ926]

1 hour ago, WRQW589 said:

Is there an MRI facility anywhere nearby?

 

In March, I went for an MRI. On my way to the facility my GMRS radio was on in the car, because I'm a boring person, like that.

 

When I got within three miles of the facility I started hearing buzzes, blips, and other strangeness on channel 17. I didn't think too much of it, until I was actually IN the MRI machine. Then I realized I was hearing the exact same sounds, the same buzzes, blips, and tones. It wasn't just similar, it was as if the GMRS radio was picking up the MRI machine's noises exactly as they sounded to me.

 

These things are supposed to be shielded, but apparently not well enough in some cases. After my MRI as I was driving home, I heard the exact same tones, until I got about three miles away from the hospital.

That's one heck of an EMI field if it causes interference up to 3 miles away.

[tweiss3]

4 hours ago, WRYZ926 said:

That's one heck of an EMI field if it causes interference up to 3 miles away.

Not really, its extremely controlled, but typically anywhere between 500W and 2000W, even some go up to 8000W, but very controlled.

You have to remember, the shielding in an MRI room is to keep RF out to get a clean picture, not to keep RF in. The typical 100db isolation is enough to keep wifi, bluetooth, cell phones and other RF out of the imaging, but the RF does leave the room.

[WRYZ926]

2 hours ago, tweiss3 said:

Not really, its extremely controlled, but typically anywhere between 500W and 2000W, even some go up to 8000W, but very controlled.

You have to remember, the shielding in an MRI room is to keep RF out to get a clean picture, not to keep RF in. The typical 100db isolation is enough to keep wifi, bluetooth, cell phones and other RF out of the imaging, but the RF does leave the room.

That's still a large EMF considering a non suppressed 25Kw 208 3 phase generator only produces an EMF of a 150 foot radius.

[WRQW589]

18 hours ago, WRYZ926 said:

That's still a large EMF considering a non suppressed 25Kw 208 3 phase generator only produces an EMF of a 150 foot radius.

I agree. I mean I don't understand the numbers behind it. But it's a pretty powerful unintentional signal. However, there was no mistaking that sound, whether it's as I lay in the MRI machine, or as I'm driving off with my GMRS radio picking it up. I don't hear it driving past other hospitals, so there must be something different about the Park City IHC hospital / imaging lab.