Securing a repeater

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Securing a repeater

Post by LincolnMan » Fri Jul 09, 2004 7:56 am

We have had a commercial repeater service (UHF conventional) for the past 3 years, One of our former employees (who is also an amateur radio operator) has been jamming our repeater for the past 3 years as well, every weekend he will come over the radio and scream obsenities and racial slurs, basically causeing a large disturbance, ignoring him does no good as he just keys up all the time and sings stupid songs and hits DTMF tones. Within the last month we changed our repeater service to another provider, it took him a week to find us and start up again, so we added 10 more repeater channels all on different frequency pairs, he found all them too, the FCC or local law enforcement will not do anything about it. My idea was to secure the repeater somehow only allowing our radios to access the repeater, since we need to stick with a conventional system for now due to all of our 25 GE MPA's are conventional. We did purchase 7 Kenwood TK-880's with the future in mind but we have to stick with the MPA's for portables for the time being. My idea to secure the repeater includes a non standard offset, something that a ham radio HT couldnt be programmed to, as well as split access tones, preferably PL on the input and DPL as the output, my question is if there is any particular repeater shift we could use that amatuer equipment could not use?

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Re: Securing a repeater

Post by Two way repair man » Fri Jul 09, 2004 1:05 pm


That is a difficult problem to resolve. The only thing that I could recommend that would allow you to use your current radios would be to switch to a new or one of the newer frequencies and install voice scramblers into all of your radios. The repeater should pass the scrambled data or voice without causing any problems, at least in most cases. The cheapest type of scrambling is simple voice inversion but it can be the easiest for your culprit to install in his HT. The best is a rolling digit code but it is the most expensive.

Please contact me directly if you want to know more.




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Post by Uncle Zhenya » Mon Jul 12, 2004 2:02 am

The best way to solve your problem is to record that guy's sayings, find his location and punish according to the law.

There is something else you can do right now.
1. Leave the repeater transmit frequency unchanged (it's easy to find), change the repeater receive frequency by any odd step not equal to 1MHz.
2. At the same (!) time use DPL to access the repeater. It's over 100 codes, not so easy to find. The disadvantage is DPL decreases the service area and increases repeater access time. Or use the non-standard PL tone (KENWOODs can do it), it's better. Standard PL is usable on the output, he'll find it soon or late anyway.
3. Use different (!) input and output tones.
4. Force your local authorities to punish your offender.

Good luck !

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Post by 963Expert » Mon Jul 12, 2004 4:10 am

Using DPL makes it a bunch harder for the average HAM radio to get into your system, the vast majority of radios out there don't have DPL. I would recommend that you use different transmit and receive DPL, just to make it one step harder for him, if he has a decoder.

As far as using unusual splits, the truth there is that HAM radios are actually better designed for unusual splits that most commercial radios and the operator can do this on the fly, I wouldn't say that is a very good fix.

Local law enforcement has very little power over the airwaves. Some states have laws which make malcious interference of communications illegal, but most local level law enforcement has no way to enforce it. They rely upon the technical crowd to assist them in this type of enforcement.

Certainly large amounts of recording, particularly if you can easily identify the suspect are great. If indeed this guy is a licensed HAM radio operator, he's apt to loose his license, but even more of a threat is the large fines/imprisonment that he would receive if the FCC were to get enough information

Unfortunately the FCC isn't too responsive to these types of complaints. They don't have enough resources to travel around the country and take action on every rogue ham-bone out there. Who is responsive to the problem is the HAM community themselves. They pride themselves on "self-policing". I don't know where your located, but I'm willing to bet that there is an organized ham radio group somewhere in your area. They probably have tons of recording and direction finding equipment to track down violators on their repeaters.

Try contacting a local HAM group, because if enough of them share recordings and findings with the FCC, they WILL take action at that point in time. Particularly if the group is affiliated with the ARRL. The FCC figures that it costs nothing to bring a group of HAMs into court, where their enforcement agents would charge overtime.

Hope this is of some help to you, I know it's a frustrating problem, I have several conventional repeaters some even on the HAM bands that give me fits.


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Post by EKLB » Sat Jul 17, 2004 5:50 pm

Well this is a problem indeed.

You cant just go out and change the freqs of a repeater legaly per FCC license.

The FCC has already put a 5 mhz spacing as on UHF repeaters per specifications .

Even if you did change the PL tone around to non standard PL or DPL tone or mix match ect = you wont stop him from transmitting over you.

What ever you do to stop him from accessing the repeater will do only that and he still can tx over you while your transmitting through the repeater since you have accessed it.

Id say he will do this even if you do scramble the audio and swap tones/DPL ect.

Im not advocating anyone to go out and do what im about to type .

But an individual that has this low of respect for other radio users ect deserves to have sombody sneak up to his base stations coaxial cable or his mobile and drive in a small needle through the outer plastic covering making sure it contacts the center wire with the outer grounded shield making sure the pin is pushed in under the outer plastic so it wont easily be seen. ( Sorta raises %*#@ on the PA and finals)

:ignore: :ignore: :ignore: :ignore: :ignore: :ignore: :ignore: :ignore:
Your probably better off recording the audio of this individual and distributing the tape around the comunity and see if you could embarass the offending individual and possibly with the comotion the tape should bring to attention someone that may decide to get involved and help out a bit more.

This aproach would be a bit more tactful rather than destroying his property and putting you in court for property damages /tresspassing ect.

The other thing is the individual doing this does not have the right to transmit on your freq without a valid FCC license.

However if by chance your licensed as a GMRS repeater that is another box full of worms as he then may have a GMRS license as well and they allow all GMRS freqs on one license now.

But that does not allow him to be a nusance to cochanel users.

This truly can be a real PITA !

Good luck and do think through all the reprocusions of anything you decide to do first = you dont want it back firing onto your self.


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Post by thor » Fri Jul 23, 2004 12:49 am

You could use MDC-1200 as you repeater access. Im sure you could get encoder's for your older radios and a decoder for the repeater.

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Post by mike m » Sat Jul 24, 2004 3:18 pm

or since you have ge MPA and don't want to get rid of em, use a GE-STAR or T-99 aftermarket signalling board on the rptr, the MPA's already have this built in.


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Post by KF4SQB » Thu Jul 29, 2004 12:56 pm

Only problem with any signaling system is that once a "valid" user keys the system, the rouge can simply key over them. A much more satisfying, although EXTREMELY illegeal, solution would be to track him down, beat the $#!^ out of him with his own radio, and then burn his radio equipment in front of him!

On a more serious note, didn't the FCC grant some enforcement authority to "local" law enforcement?
Brett Kitchens

kf4sqb "at" wetsnet "dot" com

Of all the things I've lost, it's my mind I miss the most.......

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Post by LincolnMan » Mon Aug 02, 2004 11:52 pm

yeah I thought they did but local law enforcement blows me off and wont even talk to me about it, yet when someone did the same thing to their radio they made a joint effort between 3 agencies to find the guy.

the funny thing is, the guy in that article (I know him) is in prison right not for assault weapons, and the guy who has been doing this for the past 3-4 years calls himself "The Phantom". I have alot of evidence to pursue my own investigation now, a couple nights I decided to conversate with him on our channel and got tons of good information on him, found that he is a CBer and frequents a local channel, he knows a total of 3 people I know, and he transmitts while mobile from 1 particular part of town, all I need to do is start letting people within the CB community listen to the tapes we made of him and someone has to know who he is.

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Post by nmfire10 » Wed Aug 04, 2004 1:54 pm

I like the idea of a midnight operation to sabotage his equipment. Perhaps a small EMP device outside his house?

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Ham rigs.

Post by Cowthief » Sat Sep 11, 2004 7:20 pm


My ham talkies, kenwood Th-f6a and yaesu VX-7r, can all do PL and DPL,
as well as several other signalling formats.
A ham rig, as it was pointed out, can do whatever split you want, some can even full-duplex in 2 bands.
In a word, screwed.
I would really ask myself, why is this person so ticked off at your people? or is the something that happens to everybody he meets?

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