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Building a GMRS repeater

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ThomasB3131

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There is actually a work around so that you don't hear the message twice.

Set up the simplex repeater with a different TX and RX CTCSS tones. The mobiles then would use the tones transposed in TX and RX.

The drawbacks? Those cheap Midland radios won't work. And you lose the benefit that art times the direct path between simplex mobiles is the more favorable path.

I think with the above mentioned methods, one could put up a pretty decent "machine". Again, I think with a little bit of experimenting and some decent GMRS equipment one could achieve the desired results.
 

RFI-EMI-GUY

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When I read "Hey I got a couple Baofengs and an ID-O-Matic controller and want to build a repeater", I cringe.

Folks building their first duplex repeater underestimate the details required to prevent the transmitter from desensitizing the receiver. And fewer have access to the equipment to test transmitter noise/receiver desense (TNRD) , let alone tune a duplexer. A simplex repeater is probably a good fit for a small or portable repeater requirement.
 

DeoVindice

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When I read "Hey I got a couple Baofengs and an ID-O-Matic controller and want to build a repeater", I cringe.

Folks building their first duplex repeater underestimate the details required to prevent the transmitter from desensitizing the receiver. And fewer have access to the equipment to test transmitter noise/receiver desense (TNRD) , let alone tune a duplexer. A simplex repeater is probably a good fit for a small or portable repeater requirement.

I was considering a duplex repeater installation in my truck for use while camping or prospecting. I ultimately came to the same conclusion as you and opted for a simplex repeater instead. It's trivial to configure the mobile as a repeater, just unplug the mic, plug in the repeater controller and power it on.
 

russbrill

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Yep. His response kind of made me temporarily give up on GMRS as well. Who wants to go through all that to install a repeater who’s brand new? I started even looking at where I can get GMRS repeaters to put one up on my roof and it looks like there aren’t any available for sale new. Looks like simplex MURS with an antenna on my roof to improve a bit of range might be what I’ll end up doing for just a few miles range.

My in-laws are about 5 miles away. Not sure if that would even work with an antenna on both roofs.

To answer your question; there is a company that makes a repeater capable of working on GMRS. The company is Bridgecom Systems, but before you make a purchase, you'll want to visit a website called "Repeater Builder". On Repeater Builder you will learn the "Ins and Outs" of building a repeater system. view Repeater Builder here The Repeater Builder's Technical Information Page™ ...
 

RFI-EMI-GUY

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I just bought a Kenwood TKR840-1 repeater for $330 (shipped) on the e-bay. It is a 5 watt continuous duty repeater (wideband/narrow band) with excellent receiver specs and integral controller with multi CTCSS DCSS. For high power it will need a TPL type amplifier added to it. The other great thing is that it has Part 95 certification. Kenwood makes some other fine repeaters, the similar TKR-830 (requires an external repeater controller) and the TKR-850 which is a high power repeater.

There are a lot of excellent part 95 certified repeater options at little expense if one wants to use proper radios. You will have to additionally budget a proper duplexer, transmission line and antenna.
 

mmckenna

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To answer your question; there is a company that makes a repeater capable of working on GMRS. The company is Bridgecom Systems, but before you make a purchase, you'll want to visit a website called "Repeater Builder". On Repeater Builder you will learn the "Ins and Outs" of building a repeater system. view Repeater Builder here The Repeater Builder's Technical Information Page™ ...

Bridgecom's are OK. I inherited a system of 3 of them at a remote site. Pretty easy for someone to set up with a bit of skill. You can get internal duplexers, tuned by the dealer, for around $1K. But they are just two UHF radios in a box with a controller, power supply and duplexer. Not outstanding repeaters, but often "good enough".

But like RFI-EMI-GUY said, there's cheaper solutions.
 

russbrill

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Bridgecom's are OK. I inherited a system of 3 of them at a remote site. Pretty easy for someone to set up with a bit of skill. You can get internal duplexers, tuned by the dealer, for around $1K. But they are just two UHF radios in a box with a controller, power supply and duplexer. Not outstanding repeaters, but often "good enough".

But like RFI-EMI-GUY said, there's cheaper solutions.

I know what you mean about "Quality", the Bridgecom's are okay, but I believe their market is the customer that needs a "Turn-Key" solution for their installation, and the system will be "Amateur" or "GMRS" not commercial.
 

russbrill

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Bridgecom's are OK. I inherited a system of 3 of them at a remote site. Pretty easy for someone to set up with a bit of skill. You can get internal duplexers, tuned by the dealer, for around $1K. But they are just two UHF radios in a box with a controller, power supply and duplexer. Not outstanding repeaters, but often "good enough".

But like RFI-EMI-GUY said, there's cheaper solutions.

BTW: It's my gut feeling that in the future GMRS repeater operation will be a thing of the past. I'm guessing, but we may see the return of Class A CB reintroduced by the Commission. Remember, back in the 50's the FCC originally wanted CB on UHF, but the cost for the equipment would have been out of sight, so they settled on 27 MHz...
 

RFI-EMI-GUY

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BTW: It's my gut feeling that in the future GMRS repeater operation will be a thing of the past. I'm guessing, but we may see the return of Class A CB reintroduced by the Commission. Remember, back in the 50's the FCC originally wanted CB on UHF, but the cost for the equipment would have been out of sight, so they settled on 27 MHz...

Hopefully not.

Only by encouraging folks to obtain GMRS licenses (as opposed to buying license by rule bubble-pack radios) will the GMRS service thrive.

The GMRS service is the only high performance citizens radio service available to individuals that can use high performance equipment and can be deployed in ad-hoc manner very cheaply. The threat is that GMRS sits within prime Part 90 "real estate" and the FCC has already allowed incursion into the guard bands by Part 90.

Australia has a 477 MHz UHF CB service that is very popular. They also have repeaters, though they require special licensing and the T/R duplex spacing is very minimal.
 

russbrill

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Hopefully not.

Only by encouraging folks to obtain GMRS licenses (as opposed to buying license by rule bubble-pack radios) will the GMRS service thrive.

The GMRS service is the only high performance citizens radio service available to individuals that can use high performance equipment and can be deployed in ad-hoc manner very cheaply. The threat is that GMRS sits within prime Part 90 "real estate" and the FCC has already allowed incursion into the guard bands by Part 90.

Australia has a 477 MHz UHF CB service that is very popular. They also have repeaters, though they require special licensing and the T/R duplex spacing is very minimal.

If you look at the way a lot of the GMRS equipment is marketed to the consumer, it seems to promote basic two-way operation without repeaters. I have watched several youtube videos on the Midland product line, and again the video promotes the basic two-way features of the radio, nothing fancy like repeaters. In fact, some of the youtubers don't seem to understand the Repeater concept at all..
 

RFI-EMI-GUY

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If you look at the way a lot of the GMRS equipment is marketed to the consumer, it seems to promote basic two-way operation without repeaters. I have watched several youtube videos on the Midland product line, and again the video promotes the basic two-way features of the radio, nothing fancy like repeaters. In fact, some of the youtubers don't seem to understand the Repeater concept at all..

It does not help that Midland is selling "watered down" "GMRS" radios that have only narrow band transmitters. I like the radios they make from a size and feature perspective, but won't recommend them for the reason they are narrowband. They are FRS radios with higher power. There are other options if you seek them. I have a fine Kenwood repeater here that is part 95 certified.

If you think of the big picture, the manufacturers really don't care for an individually licensed GMRS service. They would rather it be licensed by rule. If then, the GMRS licensee numbers decline, the FCC might realocate the spectrum to Part 90, and move it somewhere else like T band and then Midland and Motorola can sell new "GMRS" radios to replace them. "REAL" GMRS is like that great little 70 year mom and pop coffee shop that is adjacent to Starbucks and McDonalds in a strip mall. If the big guys want more seats, out you go.

The solution is to grow the numbers of GMRS licensees and the numbers of repeaters.
 

russbrill

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It does not help that Midland is selling "watered down" "GMRS" radios that have only narrow band transmitters. I like the radios they make from a size and feature perspective, but won't recommend them for the reason they are narrowband. They are FRS radios with higher power. There are other options if you seek them. I have a fine Kenwood repeater here that is part 95 certified.

If you think of the big picture, the manufacturers really don't care for an individually licensed GMRS service. They would rather it be licensed by rule. If then, the GMRS licensee numbers decline, the FCC might realocate the spectrum to Part 90, and move it somewhere else like T band and then Midland and Motorola can sell new "GMRS" radios to replace them. "REAL" GMRS is like that great little 70 year mom and pop coffee shop that is adjacent to Starbucks and McDonalds in a strip mall. If the big guys want more seats, out you go.

The solution is to grow the numbers of GMRS licensees and the numbers of repeaters.

Some quick numbers: California GMRS Licenses 9372, Amateur over 99,000.. Hawaii Licenses GMRS 229, Amateur over 4400...

I think the GMRS License is in trouble, I'll bet you there are more bootleggers on GMRS than license holders...
 

bill4long

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But like RFI-EMI-GUY said, there's cheaper solutions.

Couple of TYT-9000, Allstar based Raspberry Pi controller, URI interface, chicom mobile duplexer, approximate cost $400.
And it works. It really really does. For a while, cuz those radios die within three years, period. And they can't be repaired.
Upgrade to Alinco 135, 235, 435, radios and it will last forever. For $200 more bucks. Of course, use some used GM-300 and you can get the total cost to about $300 and will also last forever. If you want to deal with what is involved with programming and interfacing with Motorola radios.
.
 

n1das

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Some quick numbers: California GMRS Licenses 9372, Amateur over 99,000.. Hawaii Licenses GMRS 229, Amateur over 4400...

I think the GMRS License is in trouble, I'll bet you there are more bootleggers on GMRS than license holders...

Licensing is representation, among other things. The FCC likes to quote license data statistics in actions such as an NPRM. I agree that we need to increase the number of GMRS licensees to help the radio service survive. "Use it or lose it" applies.

If you think of the big picture, the manufacturers really don't care for an individually licensed GMRS service. They would rather it be licensed by rule.

With what the manufactures are offering, they are essentially pushing GMRS toward being made license by rule and rendered a bubble pack only service without repeaters. The 22 channel FRS as it exists today under the revised Part 95 rules will be all that remains.

In 2003, I homebrewed a GMRS repeater from UHF Part 90 mobiles (w/duplexer, etc.) and it worked well. It was one of 3 GMRS repeaters I had in service at the time. The other two were a Kenwood TKR-820 and a TKR-850. In 2011, I re-purposed the homebrewed repeater as a 440 ham repeater. It was in service as a 440 ham repeater until about a year ago when it was replaced with a DMR repeater and put on the Brandmeister Network. I thought about re-purposing the homebrewed analog repeater back to a GMRS repeater again but decided against it because it's not worth it given the way I see GMRS going.

With the possibility of GMRS being made license by rule by the new Part 95 rules by the 2010 NPRM, this caused me to research alternatives to GMRS/FRS and closely examine how I actually use GMRS/FRS. While I have had GMRS repeaters and have used them with GMRS licensed friends, the vast majority of our use of GMRS over the years has been for local simplex type use wherever we go. I was looking for a place to go in case GMRS were made license by rule and eliminated repeaters and rendered a bubble pack only service. Thankfully that has not happened.......yet. I see GMRS being pushed that way given what the manufacturers are offering.

While researching alternatives to GMRS/FRS, I was also interested in new technology and hungry for a practical digital solution. I have already been bit by the digital radio bug on 2m and 440 as a ham. I would love to be able to use DMR, NXDN, and P25 digital modes legally on GMRS but that probably will never happen. This brought me to the Motorola 900MHz DTR and DLR series FHSS digital radios. They are my digital replacement for GMRS/FRS for local on-site simplex type use with family and friends because they work so amazingly well. A coworker once asked me why not just use FRS? My answer was that I have already been doing that since FRS was created in 1996 and longer than that as a GMRS licensee since 1992 and using good quality Part 90/95 commercial gear. I want an all-digital solution that is higher quality and more professional than FRS. I want a professional quality, business class digital solution. I still have GMRS/FRS and MURS as backups and for interoperability but they are no longer my default go-to modes for local on-site simplex type use with family and friends. LOL, even my wife while not a ham now prefers to use the DTRs over any analog radio, let alone an FRS bubble pack. Since migrating my local simplex ops to FHSS digital radios on 900MHz, I don't use GMRS at all anymore except for some occasional light use of FRS bubble packs with my nephews when they come to visit or we go to visit them. I almost don't use analog at all anymore for my non-ham personal communications.
 
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amphibian

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Putting together a GMRS repeater that will work for short range (1-5 miles) is not all that hard to do. If all you need is about a 1 to 2 mile or so ranges just use two portable radios, mounted in a ammo box (surf your best friend on you tube dot com) with a external antenna on top of the box and one on the bottom of the box, attached it to a 2 inch square tubing, stick it up beside the house at about 20 foot or more and get after it. You could even go as far as to hook up solar to keep a battery charged for days when you have electric loss. I've done this many many times and they work excellent for low power short range repeaters. I've even placed them on tops of buildings using one antenna on top of the box with a duplexer inside the box. Remember, it's all about height. The higher the antenna(s) the better. 5 watts at 100 feet is a lot better than 20 watts at 10 feet. I have no more than about 150 bucks tops in each one. Shop around for the box (or make one), power supply, etc on the bay. Good luck.
 

gman1971

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I saw your other thread... I am a GMRS license holder and there is a large number of repeaters linked here in the midwest where I hear people talking all the time, from Indiana to Wisconsin...
As for the 2m stuff, the VHF/UHF FM thingy is the easiest stuff to get started. Why? b/c all the hard work has been done for you so you can use a 15 dollar UV-5R to talk to others... yes, all the real hard work was done at the repeater; the people who put that repeater together had to put a lot of time, effort and money into making it so good that even your CCR 5R can work at 30 miles... Its not that 7 dollar Amazon special antenna that is so good, its the repeater's 700 dollar collinear tuned to near perfection what makes your radio talk to it. There is a lot of skill in building a repeater, and building repeaters in VHF/UHF is only the tip of the iceberg in hams (and I am not a ham, btw)... and into my next point:

As a GMRS license holder, I can tell you from my personal experience that a 5-7 mile reliable GMRS repeater (emphasis in "reliable") is going to require a very high tower and at least 25W, potentially more, along with quality feedline (heliax) don't even bother with cheap LMR400 due to PIM, in fact a lot of towers won't even let you use LMR on the tower.... you'll need quality cavities, a combiner, which are far better than the average 3dB insertion loss mobile duplexer (3dB IL means your signal is halved even before it gets to the receiver!!)... and a potentially really good antenna like a Commscope DB-222 if you live in a really hilly area. Why such expensive antenna you might ask? well, b/c most of these cheap Chinese vertical antennas will be sending all those watts straight to the clouds due to poor radiation patterns.. been there done that. Nothing in RF that is reliable comes cheap.

Then, if you want a portable-to-repeater reliability at 7 miles, even inside buildings, expect to pay very dearly for it. If you live in a hilly area, then you'll need a ridiculously high tower and an excellent radiation pattern antenna so you won't have dead zones.... to top it off, if you live in a highly congested RF area in the UHF region (TV stations, etc), you'll find out that most of the cheap radios won't work well with a "thrown together" repeater due to receiver desense, so your 7 mile range will be utopia to achieve with UV-5Rs burned to GMRS on a K1 repeater controller box.

G.
 

Sparky_one

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I've done two different setups like you mention at a resident summer camp that included lake operations. First, for 3 years I ran a simplex repeater. I put a 5-watt UHF walkie in a 4" pvc pipe with the computer controller It would record up to 30 seconds of audio. I drilled holes in the bottom for the power and coax. The coax ran back up to a Cushcraft 5/8 wave UHF vertical. All I needed to run up the antenna pole was 20AWG wire and give it 16 volts DC at the insertion point. It was flawless for the 3 years it ran. We could hit it with the 5-watt walkies from 8 miles out or 15 miles in town with the 65 watt mobile. It was on the top of a mountain though. I replaced it with a cross band repeater. We did MURS in and GRMS out. We had a grandfathered in facility GMRS license. I know, that's not really copacetic today. Before I left for good, I put together a working UHF repeater and worked with the local Motorola dude to coordinate a frequency.
 

amphibian

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As a GMRS license holder, I can tell you from my personal experience that a 5-7 mile reliable GMRS repeater (emphasis in "reliable") is going to require a very high tower and at least 25W, potentially more, along with quality feedline (heliax) don't even bother with cheap LMR400 due to PIM, in fact a lot of towers won't even let you use LMR on the tower.... you'll need quality cavities, a combiner, which are far better than the average 3dB insertion loss mobile duplexer (3dB IL means your signal is halved even before it gets to the receiver!!)... and a potentially really good antenna like a Commscope DB-222 if you live in a really hilly area.

Let me say up front that this is not meant to be argumentative.... Only for trying to understand what I might be missing....


If this is true, then explain to me why my 10 watt (as measured at the antenna RF port of the radio) repeater that is made from two midland 8 channel mobiles, with a duplexer, that's attached to one end of 50 feet of RG6, that the other end is attached to a homemade Ladder-line antenna that's encased in a 5 foot piece of PVC (one I made for use on GMRS), and that said antenna is mounted on top of a 20 foot section of conduit that's attached to the side of my motor home ---- is working solid 10-12 mile radius of my motor home using handhelds? Now grant you, where the motor home sits is on a hill with an elevation of 596 and the surrounding area is below that, in some cases way below, but still even so, according to your "personal experience" it should not be working worth a darn.

Also, the most expensive part of this build was the 25 bucks I gave a man for the duplexer. All total, I have around a max of $150.00 in this build.

Now I have built, installed and maintained many of these things I like to call "PVC Repeaters" over the years. These PVC Repeaters are generally nothing more than 2 portable radios (many of which are a max of 3 watts if I'm lucky), my own designed repeater controller (a simple switching transistor), with a 7ah battery, solar charge controller, solar panel, all usually installed within a piece of five foot PVC with end caps, that in most cases are usually thrown up into the tops of trees or mounted to a pole that is then raised to anywhere from 20 to 40 foot in the air and I've yet to have any complaints on how well they work. I've even had some of these mounted to pipes on top of tall buildings for use as a portable "weekend use" repeater for volunteers that do traffic control at parades and such and have gotten great verbal returns on said devices.


I guess that it's simply that I don't understand, after 30+ years within the RF field, why people are always pushing this idea that unless you spend thousands of dollars up front for equipment and then spend big time money each month for tower space that a 1-10 mile radius of coverage repeater system like I've suggested in the past or mentioned above just won't work.

I guess what I'm missing and maybe not accepting is what a person said earlier about how too many people put way too much thought into this stuff and make it way too complicated not only for themselves but for others.

What ever works for some may not work for others ---- I've been told.
 

gman1971

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@amphibian

First off, I am glad it works for you.

...and there is nothing to argue here, all your talk about antenna ladder line, blah blah blah, all moot point the moment stated the 596 feet elevation figure... all you need is altitude to have range, period, and which you seem to have, but I don't. And no amount of expensive equipment will make up for the lack of elevation beyond certain point, so, in order to maximize whatever range I can muster I need better receivers, better filters, etc. Still no match for placing the antenna 400 feet in the air... but 7 miles is better than 1 mile range.

So you know, I tested the same exact UHF setup I have at home but mounted on my car; using a cheap 1/4 wave mag-mount sitting atop a pretty high elevation and I've more than easily managed 30+ miles car to car on 50W UHF GMRS... unfortunately tho, I don't have a 320 feet tower handy at my property to install the antenna at, what would be, an equivalent AGL to that car radio range test.... so there you have it.

G.
 
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