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DMR Interference on GMRS

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DeoVindice

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Myself and several other users have been experiencing intermittent interference on most of the GMRS repeater outputs, especially 462.550. It's also been present on the 462 MHz interstitials. I'm hearing the typical DMR constant "machine gun" noise along with pulses that last for a couple seconds each like a MOTORBO rest channel. It will often overpower analog voice transmissions made over a repeater. Using DCS rather than CTCSS has reduced but not eliminated the issue.

Location is Graham County, Arizona. We suspect an issue with one of the mine repeaters on Freeport McMoRan's system as they are a known Capacity Plus user. Their system has numerous frequencies licensed in the 461 and 463 MHz range. What confuses me is that this is occurring with commercial gear like TK-8180s; front-end overload from a site ten miles away seems like a bit of a stretch. I'm guessing the FCC won't be much help here, but suffering diminished use of frequencies I'm licensed for isn't really acceptable.
 

sallen07

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I'm hearing the typical DMR constant "machine gun" noise along with pulses that last for a couple seconds each like a MOTORBO rest channel.

We suspect an issue with one of the mine repeaters on Freeport McMoRan's system as they are a known Capacity Plus user.

Do you have (or have access to) a scanner that can decode DMR? That might help you confirm your suspicion.
 

littona

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Know anyone with a DMR portable? My BTech DMR-6X2 will decode anything DMR. All you have to do is put in the frequency and set it to monitor both slots. Anything that comes across will display on the screen with radio ID, color code, and slot number. Not to mention it'll decode the audio too. That should help narrow it down.
Anytone makes similar radios... they're all made in China and rebranded ever so slightly.
 

DeoVindice

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Yes, another affected GMRS licensee has a DMR portable he plans to use to figure out what's going on. I have an RTL-SDR that I might try as well.
 

DeoVindice

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You sure somebody doesn't have a DMR repeater set up on GMRS? Front-end overload does not sound right.

Honestly? No, I'm not sure. I wouldn't be shocked if the mine radio shop put a portable repeater on GMRS frequencies to support an expansion project.
 

tweiss3

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Honestly? No, I'm not sure. I wouldn't be shocked if the mine radio shop put a portable repeater on GMRS frequencies to support an expansion project.
I just ran into this where I am, and it turned out to be a DMR repeater on GMRS. No FCC ID heard on analog or anything, but just completely trashed the entire channel. I've found out at least 1 of the user's information, still trying to find the location of the repeater, though passively right now.
 

alcahuete

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Honestly? No, I'm not sure. I wouldn't be shocked if the mine radio shop put a portable repeater on GMRS frequencies to support an expansion project.

You would have to do some basic direction finding to see if it's even the mine. Normal people run DMR on GMRS frequencies somewhat regularly here in California. I have even heard some P25 on rare occassion.
 

GlobalNorth

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From the FCC website on enforcement of private LMR systems:

"The Enforcement Bureau's Regional and Field Offices, are responsible for responding to interference complaints involving private land mobile radio stations."
...

"The Enforcement Bureau encourages Private Land Mobile Radio Station licensees wishing to file interference complaints involving private land mobile radio operations to submit such complaints directly to the appropriate FAC in accordance with the process set forth in the relevant Memorandum of Understanding."




Summation: Yes, we have the power to enforce our regulations, but take your complaint to a private association and complain to them... we don't want to be bothered.
 

tweiss3

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From the FCC website on enforcement of private LMR systems:

"The Enforcement Bureau's Regional and Field Offices, are responsible for responding to interference complaints involving private land mobile radio stations."
...

"The Enforcement Bureau encourages Private Land Mobile Radio Station licensees wishing to file interference complaints involving private land mobile radio operations to submit such complaints directly to the appropriate FAC in accordance with the process set forth in the relevant Memorandum of Understanding."




Summation: Yes, we have the power to enforce our regulations, but take your complaint to a private association and complain to them... we don't want to be bothered.

This is hilarious........

I read that guide, and went to the site provided for EWA, and this is their stance:

I Know Who Is Interfering With Me; What Do I Do?
Licensees should attempt to resolve instances of interference directly before contacting EWA. If you believe you know who is interfering with your system, contact them, determine if they are the source and if so, work to resolve the problem. If that attempt is unsuccessful, please contact EWA.

If you need assistance in identifying the licensee that may be responsible, EWA can provide you with a list of adjacent and co-channel licensees in your area. EWA will complete a 120 Kms (75 miles) search of the licensees within your licensed area of operation. The search results provided to you will include the frequency, licensee name, call sign, and distance from your site. EWA’s Co-Channel User Report is $100. To request the Co-Channel User Report, use EWA's Interference Resolution Report.

With the report you can now contact the responsible person at the interfering station to resolve the interference.

Interference Mediation
If you are unable to resolve the matter directly EWA will contact the identified party to assist in the mediation of the interference. However, after EWA’s mediation it may be necessary to refer the case to the FCC’s Enforcement Bureau for resolution.

EWA’s fee for Interference Mediation is $495.You can request EWA’s assistance by completing the Interference Resolution Report with the required information and payment of the fee.

After review, EWA will act as a mediator between the offending licensee and you to determine a course of action to eliminate or minimize the interference. EWA will provide a report of the actions taken and of the final resolution of the interference. Again, the final course of action could be the referral of the interference case to the FCC Enforcement Bureau.

Interference From An Unknown Source
When you experience interference that is some form of data or is a licensee whose identity cannot be identified through the Co-Channel User Report you can request EWA to assist in identifying the source.

You can request EWA’s assistance by completing the Interference Resolution Report with all the information you have researched on the interfering signal, and submit the form to EWA. EWA will review the form, complete an analysis of the information you have provided and will conduct a review of the licensees within 120 Kms (75 miles) of the area of operation on your license. When EWA has determined that the interfering station cannot be identified or it is determined to be an unlicensed user EWA will forward the report to the FCC Enforcement Bureau for their action. EWA’s fee for this type of Interference mediation is $495.

The long and the short? FCC says don't call me, call these guys, and all they want to do is say "Have you asked nicely?" If that doesn't work its then "we can charge you more money for no resolve"
 

dwhit29689

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Yeah...back in my CB days (1970) we provided "antenna removal services" during overnite hours. What a riot.
 

Thunderknight

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Summation: Yes, we have the power to enforce our regulations, but take your complaint to a private association and complain to them... we don't want to be bothered.
This is more around two part 90 licenses with co-channel interference issues, for example spaced too short.
It is not for the unlicensed interference type issues. The reference on the FCC page is to a Part 90 rule, not a part 95 rule.
 

GlobalNorth

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I stand by my assertion that belief in privatization of certain government functions; especially in arbitration, enforcement, and mediation is a fool's dream. It places the economically disadvantaged outside of the abilities to seek redress to those wrongs against them and disadvantages those who seek correct justice.
 

RFI-EMI-GUY

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You might look into this link to see how to file a GMRS interference complaint. Otherwise submit as an LMR interference problem and let the FCC handle it. Part 90 users illegally using part 90 DMR equipment on GMRS is a legitimate complaint.

 

RFI-EMI-GUY

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I should add, be sure it is truly interference on channel and not IM or harmonic as result of using cheap receivers.
 

DeoVindice

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I should add, be sure it is truly interference on channel and not IM or harmonic as result of using cheap receivers.

This is what's bugging me. It's been a few months since I've used my SDR, but I didn't remember seeing digital signals in the GMRS allocation at that time. Close to it, absolutely - The other users in my area are using cheap receivers, but I'm operating relatively new Kenwood and EF Johnson hardware. I only experience this issue with a mobile or base installation; rubber ducky portable antennas are inefficient enough that the interference only occasionally breaks squelch. Obviously signal strength is relatively weak which is why I suspect distant and/or low power LMR gear. There are several potential culprit sites ranging from 12 to 30 miles from me.

Unfortunately I'm working this Friday thru Tuesday so fox hunting will have to wait. My plan is to start hunting it with my SDR and possibly acquire a UHF yagi to RDF it once I have some time off.

Now, take a look at WQPP866. They're licensed for 100W PEP, 20W ERP on 462.525, about as adjacent-channel as it gets. The site in question is approximately 30 ground miles from me with some intervening terrain which would explain the apparently weak nature of the signal. I think I may have identified the culprit but further work is warranted.
 

dlwtrunked

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From the FCC website on enforcement of private LMR systems:

"The Enforcement Bureau's Regional and Field Offices, are responsible for responding to interference complaints involving private land mobile radio stations."
...

"The Enforcement Bureau encourages Private Land Mobile Radio Station licensees wishing to file interference complaints involving private land mobile radio operations to submit such complaints directly to the appropriate FAC in accordance with the process set forth in the relevant Memorandum of Understanding."




Summation: Yes, we have the power to enforce our regulations, but take your complaint to a private association and complain to them... we don't want to be bothered.

I smile when people think the FCC will help. They do not have the manpower or money to go after the many cases of similar problems. Contacting them is a waste of time. In my case, years ago, when I lived in CT, a building under constructing collapsed trapping 30 people, and similar interference problems were greatly hampering rescue efforts. I called the FCC and they told me what is in the second paragraph above.
 
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