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Significant increase in users on repeater inputs

interferference uplink input repeater

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#1 intermod

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Posted 21 December 2018 - 06:36 PM

The Northern California GMRS Users Group (NCGUG) has started to see an uptick in direct mode/simplex users on our repeater inputs over the past month.  Some are not encoding tone, other are using 88.5, D031, D606, D172, and a few others.  

 

Has any new programmable radio been released that is different than those that came before?  Or one that ships with the 467 MHz uplink channels configured/configurable for Direct Mode?   

 

This may also be a growing lack of understanding of these channels?  As our repeater receiver is at 2,200 ft. AMSL, it easily hears handheld radio users within a 20-30 mile radius, and they can wipe-out our users when they are weak.  

 

Occasionally they use one of our active codes, so their "discreet" (and likely unlicensed) comms are being retransmitted everywhere.   

 

Normally such destructive interference was from heavily-accented maritime users at a nearby shipping port.  But these new users are all english-speakers with little to no accent, with some minor exceptions.  No callsigns are being used, and many seem to be unsophisticated radio users (which tells me some new radios are being sold with 467 MHz direct mode channels in them). 

 

Greg

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#2 berkinet

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Posted 21 December 2018 - 09:21 PM

Could it be FRS users on the interstitial channels with either crappy transmitters or in wide band mode?


Everything we hear is an opinion, not a fact. Everything we see is a perspective, not the truth.

-- Marcus Aurelius


#3 Radioguy7268

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Posted 22 December 2018 - 09:57 AM

Some DPL codes can be "falsed" by tone codes on certain panels. I recall seeing DPL 125 being falsed by tone code 1A on a Zetron 38 panel years back. Drove me nuts, because the interfering signal originated almost 90 miles away.

 

I was looking at reprogramming nearly 80 mobiles if I had to switch codes.  A little experimentation on the bench led to us switching tone panels and reducing receive system sensitivity a few ticks. One trip to the tower site & 30 minutes later, problem resolved.



#4 quarterwave

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Posted 22 December 2018 - 10:03 AM

Might also consider mixing. Is there something new on the air at the site or near that is mixing with 467 to produce the apparent access? Something using those codes on an adjacent frequency?

 

In the past I would suspect a paging transmitter, but that is a bit dated. I realize you insinuate that it is FRS type users, so it seems to be more in band than say a low band and VHF channel blending to produce a UHF. I can remember IMTS and Paging channels making some UHF receivers nutty back in the day. 



#5 intermod

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Posted 22 December 2018 - 01:20 PM

Could it be FRS users on the interstitial channels with either crappy transmitters or in wide band mode?

 

I have definitely seen this, but they were usually very distorted - these users were right on frequency. 


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#6 intermod

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Posted 22 December 2018 - 01:29 PM

Some DPL codes can be "falsed" by tone codes on certain panels. I recall seeing DPL 125 being falsed by tone code 1A on a Zetron 38 panel years back. Drove me nuts, because the interfering signal originated almost 90 miles away.

 

I was looking at reprogramming nearly 80 mobiles if I had to switch codes.  A little experimentation on the bench led to us switching tone panels and reducing receive system sensitivity a few ticks. One trip to the tower site & 30 minutes later, problem resolved.

 

I saw that on some ComSpec panels I had a long time ago - they also sucked at decoding DCS, and the DCS encode was noisy.   Awful things.  So I went to the Zetron 39-Max....these have been flawless.  Had one since 1995, and its still going....there is a setting for "BER sensitivity" or some such - if you tighten that up, it won't false too often.     The decoding was consistent on these users, and you could hear the DCS turnoff code as well, so they were likely DCS.   

 

I have a Zetron Model 8B desktop decoder that I have not set the sensitivity on; it heard open squelch from a TK880 24/7, and it run through all sorts of DCS (I will give Corwin Moore credit for referring me to these models - they are priceless for local decoding, encoding and control for the office).    He had two in his trashed out van....



#7 intermod

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Posted 22 December 2018 - 01:33 PM

Might also consider mixing. Is there something new on the air at the site or near that is mixing with 467 to produce the apparent access? Something using those codes on an adjacent frequency?

 

In the past I would suspect a paging transmitter, but that is a bit dated. I realize you insinuate that it is FRS type users, so it seems to be more in band than say a low band and VHF channel blending to produce a UHF. I can remember IMTS and Paging channels making some UHF receivers nutty back in the day. 

 

The site is an old Sprint/MCI or AT&T long lines site -  likely 4,000+ sq. ft. and there is only six racks left...so RF-wise its quiet.   But it does have one pager TX; likely transmitting just garbage just to hold onto the frequency for the highest bidder.   But it hits another receiver I have up there but our repeater receiver seems unaffected.     



#8 WRAF213

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Posted 22 December 2018 - 03:04 PM

Even on my home setup, I do see a lot of people (unlicensed based on communication patterns) using the GMRS inputs, one unknowingly hitting the input of some repeater on 675. I don't think it has anything to do with cheap radios being available, since none sent a 55 Hz STE tone at end of transmission. Some run CSQ, some run CTCSS. One group on 7.550 sounds like maritime users, I suspect it may be people at harbor or an oil rig given their regularity.


The best way to figure out who uses a channel is to listen closely to what they have to say. You can learn their names, location, and type of business they perform. I used it to catch some freebanders on VHF; it took a few weeks of monitoring to get enough information. I doubt the Commission would pursue the matter, even if the users are identified.

In one case, I had contacted a school regarding unlicensed transmissions on public-safety channels coming from their premises, and they determined an employee of an after-school program had purchased radios without the school's knowledge. Transmissions ceased quickly.

SDR is a powerful tool in identifying out-of-band operators. The presence, duration, and phase of end-of-transmission signalling (such as the de-facto 55 Hz tone standard) can reveal the radio model being used. Narrowband I/Q recording allows for samples to be preserved digitally and distributed for identification. Such 'fingerprints' can be determined with signal levels below -130dBm in a quiet area, and around -115dBm in most cases.

#9 intermod

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Posted 06 February 2019 - 07:13 PM

Yet again we have direct-mode users on our input.  Likely some type of Asian language.   Three users, likely mobile.  Interestingly, the Zetron repeater panel was falsing on multiple different CTCSS codes during a single transmission, on some calls.    It was not unusual for a single transmission to have generated 12 different CTCSS codes (individually).   

 

This particular Zetron never falses on voice messages.  This is similar to some of the Maritime radios we have heard for many years.  You could hear a low-level sweeping audio tone in some transmissions, but not with others in the same conversation, so it is unlikely to be some proprietary tone squelch scheme.  Maybe just a failing radio.    But this time they activated an array of repeater codes, momentarily kicking the repeater over with a syllable or two.   

 

Hope we don't lose our inputs to this.  Outputs are already gone.  



#10 Jones

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Posted 07 February 2019 - 12:25 AM

Taiwan CB Radio

It is illegal to use equipment designed for the Taiwan market in the United States.

14 channels, 12.5 kHz spacing, FM:

  1. 467.5125 MHz
  2. 467.5250 MHz
  3. 467.5375 MHz
  4. 467.5500 MHz – US GMRS Repeater Input
  5. 467.5625 MHz – US FRS Channel 8
  6. 467.5750 MHz – US GMRS Repeater Input
  7. 467.5875 MHz – US FRS Channel 9
  8. 467.6000 MHz – US GMRS Repeater Input
  9. 467.6125 MHz – US FRS Channel 10
  10. 467.6250 MHz – US GMRS Repeater Input
  11. 467.6375 MHz – US FRS Channel 11
  12. 467.6500 MHz – US GMRS Repeater Input
  13. 467.6625 MHz – US FRS Channel 12
  14. 467.6750 MHz – US GMRS Repeater Input

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#11 WPXM352

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Posted 07 February 2019 - 08:21 PM

The Northern California GMRS Users Group (NCGUG) has started to see an uptick in direct mode/simplex users on our repeater inputs over the past month.  Some are not encoding tone, other are using 88.5, D031, D606, D172, and a few others.  

 

Has any new programmable radio been released that is different than those that came before?  Or one that ships with the 467 MHz uplink channels configured/configurable for Direct Mode?   

 

This may also be a growing lack of understanding of these channels?  As our repeater receiver is at 2,200 ft. AMSL, it easily hears handheld radio users within a 20-30 mile radius, and they can wipe-out our users when they are weak.  

 

Occasionally they use one of our active codes, so their "discreet" (and likely unlicensed) comms are being retransmitted everywhere.   

 

Normally such destructive interference was from heavily-accented maritime users at a nearby shipping port.  But these new users are all english-speakers with little to no accent, with some minor exceptions.  No callsigns are being used, and many seem to be unsophisticated radio users (which tells me some new radios are being sold with 467 MHz direct mode channels in them). 

 

Greg

KAF1291

Greg; If you have repeaters on the band edge, be aware the FCC now permits part 90 NXDN operations INSIDE the lower and upper edges of Part 95, they did this against there own previous practices and despite objections. Unfortunately the GMRS community kind of snoozed on this "guard band intrusion" and now it is here. If you operate a repeater on the upper and lower pairs, and especially if you have an AFC (Micors), there may be interference. Because the FCC no longer license GMRS repeaters by site, who is to say who is the incumbent should there be a part90 vs part 95 shooting match.



#12 intermod

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Posted 08 February 2019 - 01:39 PM

Greg; If you have repeaters on the band edge, be aware the FCC now permits part 90 NXDN operations INSIDE the lower and upper edges of Part 95, they did this against there own previous practices and despite objections. Unfortunately the GMRS community kind of snoozed on this "guard band intrusion" and now it is here. If you operate a repeater on the upper and lower pairs, and especially if you have an AFC (Micors), there may be interference. Because the FCC no longer license GMRS repeaters by site, who is to say who is the incumbent should there be a part90 vs part 95 shooting match.

 

We are on 600 and are using a Motorola SLR5700 repeater with good selectivity.  This is definitely co-channel.   MRA in Socal was the first to request that and it went national; but the only think you can fit on those channel are 4K0 narrow NXDN, which is what everyone is doing.  Unfortunately, they are trunked control channels of course and on-air 24/7. 

 

Greg



#13 intermod

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Posted 08 February 2019 - 01:41 PM

Taiwan CB Radio

It is illegal to use equipment designed for the Taiwan market in the United States.

14 channels, 12.5 kHz spacing, FM:

  1. 467.5125 MHz
  2. 467.5250 MHz
  3. 467.5375 MHz
  4. 467.5500 MHz – US GMRS Repeater Input
  5. 467.5625 MHz – US FRS Channel 8
  6. 467.5750 MHz – US GMRS Repeater Input
  7. 467.5875 MHz – US FRS Channel 9
  8. 467.6000 MHz – US GMRS Repeater Input
  9. 467.6125 MHz – US FRS Channel 10
  10. 467.6250 MHz – US GMRS Repeater Input
  11. 467.6375 MHz – US FRS Channel 11
  12. 467.6500 MHz – US GMRS Repeater Input
  13. 467.6625 MHz – US FRS Channel 12
  14. 467.6750 MHz – US GMRS Repeater Input

 

 

That is good info.   And just by chance this traffic may have been Taiwanese.  Do you know of anyone selling these domestically?  

 

Greg


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#14 intermod

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Posted 08 February 2019 - 02:02 PM

Found the PRC allocations from 2005 here - word search for 467.6:

 

https://www.ncc.gov....92_070605_1.pdf



#15 intermod

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Posted 21 May 2019 - 09:27 AM

Unauthorized maritime users are now using the National Travel Tone (141.3 Hz) on our input.   Yesterday we had about nine hours of regular transmissions that were strong enough to wipe out our portable radio users.   This is the third time in about two months - same ones.  These users had no significant accents typical of other maritime users.    I believe we have filed over 110 complaints with the FCC using their Consumer Compliant site (https://consumercomp...cc.gov/hc/en-us).    They recently added a category for "Pirate/Unauthorized Operation", in addition to interference.  Nice.   

 

And the FCC does (eventually) respond with a personal phone call.


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#16 marcspaz

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Posted 21 May 2019 - 10:50 AM

If I owned the repeater, while waiting for FCC to intervene, I would just shut it off when I hear them get on it.  If I can't use it, why should they.


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#17 intermod

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Posted 21 May 2019 - 11:12 AM

We don't use the 141.3 code so it was not actually activating our repeater - just wiping out users trying to use the repeater on our normal tones.  They are running direct mode/simplex on our input, so they have no clue that they are trashing us.    But they also don't really care. 

 

intermod   



#18 marcspaz

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Posted 21 May 2019 - 11:17 AM

Ah... bummer.  That's even worse.



#19 Logan5

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Posted 21 May 2019 - 11:30 AM

We don't use the 141.3 code so it was not actually activating our repeater - just wiping out users trying to use the repeater on our normal tones.  They are running direct mode/simplex on our input, so they have no clue that they are trashing us.    But they also don't really care. 

 

intermod   

Same thing happening here in Fort Lauderdale. there is a maritime document spreading through the industry, that list 467, repeater inputs as safe to use in USA ports.


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#20 Logan5

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Posted 21 May 2019 - 12:45 PM

If I owned the repeater, while waiting for FCC to intervene, I would just shut it off when I hear them get on it.  If I can't use it, why should they.

that would not inconvenience them, as they are using simplex on the input freq. their illegal conversation will carry on unimpeded. Turning off the repeater only inconveniences legal repeater users and operators.







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