Want to set up a GMRS repeater

[FoxMcCloud]

I hold a GMRS license and I want to set up a repeater for chatting with some friends and family. Using only mobile radios at 4 watts, we can no longer hear each other after about 2 miles or so. I would like to set up rather cheap repeater to extend such chatter, doesn't need to be too special. Just doing this as a hobby. Range of 10-15 miles will suffice. Any recommendations will be greatly appreciated

 

[ko6jw_2]

There are GMRS mobiles out there that offer higher wattage. The limit is 50 watts. Constructing a repeater requires several things. The first is a radio or a dedicated repeater that can operate full duplex or be modified to do so. A repeater has to transmit and receive simultaneously. Then you need a duplexer to isolate the transmit signal for the receiver. These are not cheap. Then an antenna and a power supply. Other stuff too, but you get the basic idea. This takes serious bucks to do correctly.

My suggestion is that you look at myGMRS.com to see if someone already has a repeater in your area. There are more and more being added. You need the owner's permission to use the repeater, but the one in my area only needs to know if you are licensed.

 

[N4GIX]

...doesn't need to be too special. Just doing this as a hobby. Range of 10-15 miles will suffice. Any recommendations will be greatly appreciated

The two most important things for a successful repeater are height and antenna/feedline, neither of which is inexpensive. Note that UHF radio is horizon line of sight, so to achieve the range you want will require around 100' height above ground. Assuming a height of 5' for the antenna on a mobile or handheld only adds about 3 miles more range.

An antenna at 30' would acheive maybe 3 to 4 miles LOS.

 

[chief21]

Building a truly functional repeater is not a trivial or inexpensive task. Unless the transmitter and receiver are properly filtered (to prevent interaction/desensing), and a quality, commercial-grade duplexer is used, the range will likely be poor. And, as already mentioned, the antenna system needs to be top-notch and have some substantial height above ground level.

 

[prcguy]

In addition to the good advice others have given, unless you are familiar with building up and installing repeaters, you should hire a company to do this. It takes knowledge, experience and test equipment to set up and install a repeater and to bless its operation before handing over to a commercial customer. Once installed there is very little an end user can do to troubleshoot or fix if the repeater mis-behaves. This is not something you just experiment with on commercial or GMRS frequencies.

If you have an amateur license you can experiment all you want and that's a good place to learn. Get a mentor and the proper test equipment and learn what it takes to put an amateur repeater on the air. After you have mastered it to a level sufficient to work on commercial radios, then you can install and maintain your own commercial/GMRS repeater.

 

[FoxMcCloud]

My friend who got me into this has a technician license. When I get the chance ill let him know what I found out from y'all. I have a house atop of a hill so that would be good for this. I found a vectrex standard console unit I think would work for this, if you guys have any other hardware to recommend let me know. All the repeaters in my area, that being two are paid and rather far from me

 

[WA0CBW]

Did you mean a "vertex" standard console?
bb

 

[RFI-EMI-GUY]

I hold a GMRS license and I want to set up a repeater for chatting with some friends and family. Using only mobile radios at 4 watts, we can no longer hear each other after about 2 miles or so. I would like to set up rather cheap repeater to extend such chatter, doesn't need to be too special. Just doing this as a hobby. Range of 10-15 miles will suffice. Any recommendations will be greatly appreciated

A good resource is repeaterbuilder.com.


You biggest hurdles will be height over average terrain and duplex sensitivity, aka Transmitter Noise, Receiver Desensitization. If you can overcome these with significant antenna height and a properly designed duplex radio setup, you will be successful. If the challenge of designing a duplex repeater evades sucess, you can explore a simpler, Simplex store and forward repeater. While not as elegant, it will be functoonal.

You don't need a ham license to experiment with repeaters. Whether you do it using ham radio or GMRS, the challenges are the same. Duplex requires some engineering skills and hardware. More bucks, more Buck Rogers in that respect.

I suggest doing a lot of research of successful repeater projects before throwing something together. Hint, cheap radios have awful receivers. That can cause frustration for a duplex repeater.

Good luck on the project!

 

[Markinsac]

The site is actually www.repeater-builder.com - it is a good site - hadn't been to it for a while.

 

[wqxi846]

You should take a look at SIMPLEX repeaters systems. Not truly a repeater , but meets your 10 to 15 mile extension requirement at much less the cost and technical know how. Then use the dedicated GMRS repeater channels and you should be good to go. A good place to start. I use one on my camper and easily extends your range at lower handheld radio wattages.

 

[MTS2000des]

The biggest factor for a repeater system is the actual site. One can have the best repeater in the world (think GTR8000), preamps, best duplexers/circulators, best antenna and feedline, and unless the site has good HAAT, it will still be essentially a "backyard" repeater that may only provide a couple of miles of coverage, especially portables, if the terrain is challenging. 10-15 miles over flat land is much different than 10-15 miles over tree covered hills and valleys, or urban areas with concrete and steel.

Sites are also the most expensive part of the equation, and unless one is very lucky and lives on top of a mountain, be prepared to shell out thousands a year or more in rent to a commercial tower/site management firm like American Tower, Crown Castle, etc. The days of "cut the grass and it's yours" are long over as GOOD sites in many areas are professionally managed and the only language spoken is the one of dollars and cents a month.

Like a BMW, if you have to ask "how much", you probably can't afford it.

 

[prcguy]

In the early 80s when I was doing research before putting my first GMRS repeater up, I found wording in the FCC rules that stated the repeater must be FCC type accepted for part 95, so you could not cobble together some radios and make a legal repeater. I have not looked for this wording in recent times but at the very least the radios used to make a GMRS repeater would have to be FCC part 95. GMRS is not ham radio.

You don't need a ham license to experiment with repeaters. Whether you do it using ham radio or GMRS, the challenges are the same. Duplex requires some engineering skills and hardware. More bucks, more Buck Rogers in that respect.

 

[RFI-EMI-GUY]

In the early 80s when I was doing research before putting my first GMRS repeater up, I found wording in the FCC rules that stated the repeater must be FCC type accepted for part 95, so you could not cobble together some radios and make a legal repeater. I have not looked for this wording in recent times but at the very least the radios used to make a GMRS repeater would have to be FCC part 95. GMRS is not ham radio.

I recall similar concerns for Part 90, yet there are tons of MAXTRAC300 repeaters cobbled up, even with Motorola OEM and aftermarket RICK type controller s in Part 90 service. The concern I recall was that a Part 90 repeater needed 2 ppm stability. Were these cobbled stations equipped with 2 ppm crystals? Were they "maintained" at 2 ppm. Hard to say. Plenty of Ham repeaters with aftermarket crystals jammed into OEM holders without much thought to temperature stability.

The rules have changed many times over.

If you read closely, the current FCC specs for frequency stability for GMRS read as follows:

From Definitions:

Frequency stability. A design requirement
specifying the maximum amount that carrier
frequencies of transmitters may normally change
from their nominal value as a result of changes in
ambient temperature, power supply voltages, or
other external factors.

§ 95.1765 GMRS frequency accuracy.
Each GMRS transmitter type must be designed to
comply with the frequency accuracy requirements
in this section under normal operating conditions.
Operators of GMRS stations must also ensure
compliance with these requirements.
(a) The carrier frequency of each GMRS
transmitter transmitting an emission with an
occupied bandwidth greater than 12.5 kHz must
remain within 5 parts-per-million (ppm) of the
channel center frequencies listed in § 95.1763
under normal operating conditions.
(b) The carrier frequency of each GMRS
transmitter transmitting an emission with an
occupied bandwidth of 12.5 kHz or less must
remain within 2.5 ppm of the channel center
frequencies listed in § 95.1763 under normal
operating conditions.

So from the above; you will see that there is no special frequency stability requirement for a GMRS repeater station. As long as mobiles used meet the appropriate Part 95.1765 spec for the bandwidth used.

So if one had two mobiles that meet or exceed these requirements they could be used for a repeater. Obviously a purist would prefer Part 95 certified rather than Part 90 certified radios. I would, yet my current project will be genuine Part 95 up until the continuous duty 50W output PA. Where does one find such in this day and age that is Part 95?

I have built and continue to build GMRS repeaters from mobiles and other than the issue of maintaining duplex sensitivity, there is nothing I would consider experimentation unless building an exciter from parts. It either works or not.

If you search the FCC database for warnings and NAL's to GMRS licensees, you will find virtually nothing. That Bundy guy maybe, a slew of Ham's, but virtually no GMRS enforcement other than unlicensed business users with repeaters on GMRS.

I have seen plenty of bodged Part 90 installations in my years of auditing Public Safety radio systems. At one PD in California, three MSR2000 cabinets were lashed together to make one VHF repeater. Nice shiny dispatch consoles , shiny E911 and CAD up front. The radio room a shambles. The antenna on a phone pole outside. The radio tech apologized for being up 24 hours straight getting the MSR2000 Frankenstein working. I asked, whats with the brand new dispatch center and the crappy old radios. he said "My Boss is an IT guy, - Not a radio guy".

 

[prcguy]

There are tons of repeaters FCC type accepted for 95A use and my understanding is that a repeater must be specifically type accepted for 95A GMRS use as a repeater. Two part 95A mobile radios stuck together as a repeater are not a part 95A accepted repeater. I did read some rules specific to this years ago but have not searched in awhile. Maybe the rules changed or maybe not.

I recall similar concerns for Part 90, yet there are tons of MAXTRAC300 repeaters cobbled up, even with Motorola OEM and aftermarket RICK type controller s in Part 90 service. The concern I recall was that a Part 90 repeater needed 2 ppm stability. Were these cobbled stations equipped with 2 ppm crystals? Were they "maintained" at 2 ppm. Hard to say. Plenty of Ham repeaters with aftermarket crystals jammed into OEM holders without much thought to temperature stability.

The rules have changed many times over.

If you read closely, the current FCC specs for frequency stability for GMRS read as follows:

From Definitions:

Frequency stability. A design requirement
specifying the maximum amount that carrier
frequencies of transmitters may normally change
from their nominal value as a result of changes in
ambient temperature, power supply voltages, or
other external factors.

§ 95.1765 GMRS frequency accuracy.
Each GMRS transmitter type must be designed to
comply with the frequency accuracy requirements
in this section under normal operating conditions.
Operators of GMRS stations must also ensure
compliance with these requirements.
(a) The carrier frequency of each GMRS
transmitter transmitting an emission with an
occupied bandwidth greater than 12.5 kHz must
remain within 5 parts-per-million (ppm) of the
channel center frequencies listed in § 95.1763
under normal operating conditions.
(b) The carrier frequency of each GMRS
transmitter transmitting an emission with an
occupied bandwidth of 12.5 kHz or less must
remain within 2.5 ppm of the channel center
frequencies listed in § 95.1763 under normal
operating conditions.

So from the above; you will see that there is no special frequency stability requirement for a GMRS repeater station. As long as mobiles used meet the appropriate Part 95.1765 spec for the bandwidth used.

So if one had two mobiles that meet or exceed these requirements they could be used for a repeater. Obviously a purist would prefer Part 95 certified rather than Part 90 certified radios. I would, yet my current project will be genuine Part 95 up until the continuous duty 50W output PA. Where does one find such in this day and age that is Part 95?

I have built and continue to build GMRS repeaters from mobiles and other than the issue of maintaining duplex sensitivity, there is nothing I would consider experimentation unless building an exciter from parts. It either works or not.

If you search the FCC database for warnings and NAL's to GMRS licensees, you will find virtually nothing. That Bundy guy maybe, a slew of Ham's, but virtually no GMRS enforcement other than unlicensed business users with repeaters on GMRS.

I have seen plenty of bodged Part 90 installations in my years of auditing Public Safety radio systems. At one PD in California, three MSR2000 cabinets were lashed together to make one VHF repeater. Nice shiny dispatch consoles , shiny E911 and CAD up front. The radio room a shambles. The antenna on a phone pole outside. The radio tech apologized for being up 24 hours straight getting the MSR2000 Frankenstein working. I asked, whats with the brand new dispatch center and the crappy old radios. he said "My Boss is an IT guy, - Not a radio guy".

 

[RFI-EMI-GUY]

There are tons of repeaters FCC type accepted for 95A use and my understanding is that a repeater must be specifically type accepted for 95A GMRS use as a repeater. Two part 95A mobile radios stuck together as a repeater are not a part 95A accepted repeater. I did read some rules specific to this years ago but have not searched in awhile. Maybe the rules changed or maybe not.

I would love to know what "tons of Part 95 repeaters" exist out there. The last I checked the only one that was new was Bridgecom and getting a part 95 certification from them was like pulling hens teeth. It turns out their repeater is indeed "two mobile radios stuck together as a repeater". I am not sure Bridgecom has certified a Part 95 repeater combo, though they certainly like to advertise such.

From Definitions:

Repeater station. A station in a fixed location
used to extend the communications range of
mobile stations, hand-held portable units and
control stations by receiving their signals on one
channel (the input channel) and simultaneously
retransmitting these signals on another channel (the
output channel), typically with higher transmitting
power from a favorable antenna location (typically
high above the surrounding terrain)

If you read the most recent (2017) rules (there are many changes and some new errors) and search for Repeater, you will find that the concept is acknowledged throughout the entire GMRS rule section. However there is no specific discussion within the certification requirements stating that a repeater combo must be certified.

Whatever components are used as a repeater should be Part 95 certified. Primarily that is the transmitter.

There are some new requirements regarding marketing of new radios which I would assume would apply to new models. Specifically the radio cannot operate on frequencies other than GMRS. So if iCOM were persuaded to offer a new model repeater for GMRS service, the firmware would have to restrict the frequencies to GMRS.

I dont see the problem legally if one has two part 95 certified radios and connects them together as a repeater. The rules do not preclude doing that.

 

[prcguy]

The last time I searched for repeaters type accepted for 95A, nearly everything I grew up with from Motorola, GE and others were FCC type accepted for part 95. So I used lots of GE Master IIs, Radius R-100s and a few others that were GRMS legal. In So Cal we had at least half a dozen GMRS repeaters running on major mountain tops around here, some under my license and some under a friends plus some low level repeaters at our houses. These were all licensed under the old system with specific lat/lon, antenna heights and max power.

The list of actual repeater stations that are part 95 legal is huge, so there are a lot to choose from. My old GMRS partner still has a warehouse full of UHF repeater stuff, all taken out of GMRS service and today we only have one active repeater in So Cal which is acting up and needs attention.

I would love to know what "tons of Part 95 repeaters" exist out there. The last I checked the only one that was new was Bridgecom and getting a part 95 certification from them was like pulling hens teeth. It turns out their repeater is indeed "two mobile radios stuck together as a repeater". I am not sure Bridgecom has certified a Part 95 repeater combo, though they certainly like to advertise such.

From Definitions:

Repeater station. A station in a fixed location
used to extend the communications range of
mobile stations, hand-held portable units and
control stations by receiving their signals on one
channel (the input channel) and simultaneously
retransmitting these signals on another channel (the
output channel), typically with higher transmitting
power from a favorable antenna location (typically
high above the surrounding terrain)

If you read the most recent (2017) rules (there are many changes and some new errors) and search for Repeater, you will find that the concept is acknowledged throughout the entire GMRS rule section. However there is no specific discussion within the certification requirements stating that a repeater combo must be certified.

Whatever components are used as a repeater should be Part 95 certified. Primarily that is the transmitter.

There are some new requirements regarding marketing of new radios which I would assume would apply to new models. Specifically the radio cannot operate on frequencies other than GMRS. So if iCOM were persuaded to offer a new model repeater for GMRS service, the firmware would have to restrict the frequencies to GMRS.

I dont see the problem legally if one has two part 95 certified radios and connects them together as a repeater. The rules do not preclude doing that.

 

[FoxMcCloud]

Thank you everyone for your input, I am looking into all of the suggested methods