Help identifying this tone when using GMRS Repeater

[Guest entropywrench@gmail.com]

Hello all. 
Helping a buddy set a GMRS repeater up in the middle of the woods to see if the system will work for an upcoming event.
Our weekend test was a bit of a bust. Several of the test radios from various makers didn't reliably hit the repeater.  
Then sometimes they did, then didn't again.  Then most would but one wouldn't. Head scratching... 
All through the testing process this "tone" would start up and sometimes babble through all the radios for up to a minute. 
I should know the noise carried through our testing area better than anything else.
I'll add a link to a 12 second audio file at the bottom.

Equipment was a Retevis RT97 and a "slim jim" antenna strung 40 feet into a tree. 
We toyed with privacy on/off open repeater different channels, transmit powers, etc.
Couldn't find a combination that worked for our purposes nor could we recreate this tone on demand. 
We assume it's coming from the repeater as when we configured the test radios to not use the repeater at all. No noise just expected range issues.

Anyway, we are testing all cables, antenna, etc but in the meantime, I'm hoping you all can can help identify what that noise is what could be causing it.

12 Second Static and Unidentified tone 

Thanks in advance, Mike.  

[SteveShannon]

404 - file not found. Probably a permission thing. As a guest you might not have permission to upload files. 

[entropywrench]

Yup, I noticed that, so I registered and trying again with a direct upload and a link from G drive.
 

Offending audio in question linked and attached here:  
https://drive.google.com/file/d/1cuIFnbH_eVS-tK4AAoTZZDrSx75JxyJJ/view?usp=drive_link

Between the two it should be ok.  

My friend did hook the antenna system up to an SWR and was getting strange results. To the point where he's ordering a more specific meter. 

[OffRoaderX]

That does not sound right.  Was the signal of the noise strong, like it was coming from the repeater, or was it weak like it was something far away?

..and, poor SWR would have nothing to do with this noise, but what do you mean by "strange results"? What was the SWR reading? and what do you mean by "more specific meter"? 

[entropywrench]

It was a very strong signal and discernible from the predicted ranges of the repeater even when voice didn't work. 
We tested the radios with straight gmrs (not using the repeater) and the tone never showed up. 

The strange sound appeared with Privacy Tones On or Off. 
 
As far as the SWR, he said it was "off the charts" on the Slim Jim Antenna and when he tested his fiberglass antenna back at the farm it read "8"
However, the SWR was not for UHF so those results should probably be ignored. 

So far he's not been able to reproduce the tone back at the farm. Same repeater, same portable battery, same coax, and slim jim Antenna. 

So far though, I appreciate the help.

 

[LeoG]

Sounds like you are trying to connect to AOL by phone.

[marcspaz]

That is the sound of telemetry data, while listening to it with an analog receiver. Its very common to hear on FRS/GMRS channels in rural areas where farming is mostly still family run and they don't have big budgets for automated monitoring and control systems.

[entropywrench]

Well, maybe some logging equipment as there isn't a bit of farmland in quite some distance, well beyond the repeater. 

I here's a google maps pin of nearish were we tried the repeater.  

To further add some details, we would hear this noise on 20 or 22 repeater only with our without privacy.

https://maps.app.goo.gl/ZKxaU34Jv3kgCZ7y9   <-approximate repeater location

[OffRoaderX]

Do you hear this noise when the repeater is turned off?

[marcspaz]

Yeah, that is very odd. Privacy tones make it so you can't hear a signal unless the tone is present. You should hear the signal with no tone and it should go away when the tone is enabled, unless your radio is broken. That could be possible. You hear noise when tone squelch is enabled because the radio is broken, and you're just hearing random noises from the radio itself. 

[WRUE951]

would be interesting to get a spectrum analyzer on the signal and also try to get a heading in he direction it is coming from..  Is this signal continiouse or dependable enought ot track down..   Are you getting it on one chanel? or several channels in GMRS?  What Ch were you setting yiour repeater up?   Did you try another? I wuoild have fun tracking that one..  wish i could help, but to darn far away to hitch up and go 

[entropywrench]

We did not hear the noise when the repeater was off.

We got it on 20 and 22 when we tested. Didn't try any of the other lower power channels.

Only had the one repeater to play with. 

I toyed with squelch from 0-3 didn't seem to make a difference, the noise was always able to break the squelch

We couldn't "make" it happen, sometimes it would be just a few seconds. Another it went on for more than a minute.

All in all we had 6 hand held radios of various makes, a truck based radio.
 

The tone didn't appear when we would scan all the GMRS, MURS,etc frequencies save for the current repeater channel
 

[entropywrench]

He did hook up the rig to the SWR meter and from the looks of it.  It reads   vswr: 1.01  FW: 18.65W on 462.626mhz Trans% 99.99%  

[OffRoaderX]

4 minutes ago, entropywrench said:

He did hook up the rig to the SWR meter and from the looks of it.  It reads   vswr: 1.01  FW: 18.65W on 462.626mhz Trans% 99.99%  

SWR has nothing to do with the noises you're hearing.

[entropywrench]

equipment tests have all come back excellent. 
current working hypothesis by radio types in the area, think it might be the local mine 15+ odd miles away.

Thanks for the help all

[entropywrench]

Solution.   We figured out what that tone is:   Bluetooth.   Setting up the repeater again in the woods for the event this weekend we were disheartened to hear that tone pop back up. Baffled confused as all the tests back at the farm and in the camp group before we strung the equipment, came back fine.  While fiddling around with the rig (battery, repeater, antenna) the antenna cable was jostled and the tone went away.  The Tone is coming from the bluetooth battery monitor in the pack when the antenna was in a particular alignment with said battery pack.

In previous tests we had everything jammed into a rough tote with no issue, only when the antenna was strung 40 feet up in the trees did the problem creep up.  Weird and annoying.

Moving the antenna a few inches to the left or right, or rotating the battery pack, eliminated the problem completely. 

Repeated worked great over heavy vegetated terrain with an 10 mile radius.

 

[LeoG]

Good on you for figuring that out.

[WRXB215]

WOW! That one does sound like a hard one to diagnose.

[HHD1]

Funny how a 2.4 ghz, frequency jumping bluetooth signal would show up on 462 mhz.  I wonder about your antenna cable quality on this one.  Glad you figured it out.  Thanks for sharing.

[WRUE951]

2 hours ago, HHD1 said:

Funny how a 2.4 ghz, frequency jumping bluetooth signal would show up on 462 mhz.  I wonder about your antenna cable quality on this one.  Glad you figured it out.  Thanks for sharing.

yea, that is odd,,  5th harmonic should be measured at nothing..  

[entropywrench]

We think that when we key'd the repeater on it would pick up that 2.4ghz and rebroadcast it. As the tone did seem to require "prompting"

 

[WRYZ926]

2.

On 10/22/2025 at 5:44 PM, WRUE951 said:

yea, that is odd,,  5th harmonic should be measured at nothing..  

You wouldn't think that the repeater would pickup and transmit a signal on the 5th harmonic. I'm no expert but that makes me think that the bluetooth device is either putting out more power than it should and/or the repeater's front end is wide open.

I've had some CCR radios with wide open front ends that pick up signals on the harmonic frequencies. It's aggravating when using the radios everyday but does come in handy when trying to chase down sources of RFI.

[WRUE951]

58 minutes ago, WRYZ926 said:

2.

You wouldn't think that the repeater would pickup and transmit a signal on the 5th harmonic. I'm no expert but that makes me think that the bluetooth device is either putting out more power than it should and/or the repeater's front end is wide open.

I've had some CCR radios with wide open front ends that pick up signals on the harmonic frequencies. It's aggravating when using the radios everyday but does come in handy when trying to chase down sources of RFI.

its all fabricated..   attention getting 

[WRYZ926]

On 10/24/2025 at 9:57 AM, WRUE951 said:

its all fabricated..   attention getting 

Almost anything is possible as RF does some weird things at times.

I had people calling me a liar when I said that one of my shielded CAT6 cables had a bad ground wire and was causing interference with my HF radio.  I had to show them in person before they would believe me.

Now it is weird that the OP stated just moving the antenna and turning the battery around fixed his issue. So I'm thinking that 

A) the repeater has a very sensitive front end

B.) the battery is one of those smart batteries with Bluetooth which is messing up and causing interference.

C) there are some bad cables and/or a bad ground somewhere in the mix.

In reality, who knows what was going on with his setup since none of us were there to see it.

RFI and EMI will do weird things. I live in an old house and was getting really bad interference from my computer monitors with some of my dual band hand held radios on the 70cm band. The fix was for me to switch out my UPS battery backup systems to Tripp-Lite UPS's with built in EMI and RFI filters.

[WRUE951]

1 hour ago, WRYZ926 said:

Almost anything is possible as RF does some weird things at times.

I had people calling me a liar when I said that one of my shielded CAT6 cables had a bad ground wire and was causing interference with my HF radio.  I had to show them in person before they would believe me.

Now it is weird that the OP stated just moving the antenna and turning the battery around fixed his issue. So I'm thinking that 

A) the repeater has a very sensitive front end

the battery is one of those smart batteries with Bluetooth which is messing up and causing interference.

C) there are some bad cables and/or a bad ground somewhere in the mix.

In reality, who knows what was going on with his setup since none of us were there to see it.

RFI and EMI will do weird things. I live in an old house and was getting really bad interference from my computer monitors with some of my dual band hand held radios on the 70cm band. The fix was for me to switch out my UPS battery backup systems to Tripp-Lite UPS's with built in EMI and RFI filters.

https://giphy.com/gifs/nice-kyle-sIHj7Sm43H30s