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ANSWER.... What are the proper steps to putting a GMRS repeater on the air?


WRKC935
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Go pop some popcorn and kick back.... This WILL be a long read.

So you have you license.  Now you want to put up a repeater.  Great,,,, maybe,, usually.  But have you thought it through or do you just really want to hear your call sign coming across the airways if CW?  This is going to explain how to do it right to NOT cause interference with other repeater owners and be mindful of the limited resource (8 repeater pairs) we have been designated by the FCC.  This will cover planning, equipment, antenna's and everything in between.  Please ask questions about the topics as they are posted, and if you see something missing you would like covered, message me and I will do my level best to cover that topic.  I have been a commercial two-way radio tech for 13 years a ham for almost 30 and have been working on electronics and radios for 40 years. 

 

First thing is to listen. 

Listen to the repeater pair OUTPUTS.  These are the 462 frequencies in the 462/467 pairs.  They are what the repeaters will be transmitting on.  The reason you want to listen is you want the quietest one for your area.  Now that doesn't necessarily mean the one with the least traffic.  So if you have several repeaters around you that are not all that busy, but the signal from them is always very strong and clear and maybe a busier frequency talks alot, but is far off in the distance 4 towns over, any your plans are for a small footprint, with a 30 or 40 foot tower, that may well be the better frequency to choose.  You need to consider a couple things here.  Number one is the total number of pairs available.  We only have 8 for EVERYWHERE.  Why is that important?  Because the guys with the monsters, like me how just talked to a guy 40 miles away from his repeater, can cover huge area's with their repeaters.  And some of them see the value in what they have and allow others to use it openly.  That's my stance on it.  I say the same thing to everyone that asks.  Make sure to ID your station and have fun.  But if you are sitting on an otherwise open frequency, he may not use it for a wide area coverage machine.  I am thinking on writing a thread on frequency management at a state level for GMRS, but that comes later.  So back to the footprint you are looking to achieve, and you need to be reasonable here.  Don't decide to build a monster, tie up a pair and make the repeater closed to all but you and your wife and kids.  That's not proper use of the airways.  And in my opinion is a bit of a dick move.   SO lets say we are going to use that pair that you can hear a repeater on but it's very weak signal and can't always be heard.  You NEED to locate the owner of that repeater and verify where he is located.  If he's a weak station but he's right up the road, then don't use that frequency.  If he's 2 counties away, you are golden.  You need to find out what PL or DPL he is using on his repeater and NOT use anything close to that.   If he's running between 67 and 103 you want to be at a minimum at 141.3.  This will minimize the potential of interference.  You also need to verify that you are either very noisy into his repeater or you can't hit it at all from most of the footprint area you are wanting to cover.

Now a quick side note.  Repeater talkout (how far it talks) is controlled by two things.. first is antenna height.  Height is FAR more important than power level.  But power level does play a role.  And you ONLY want to run enough power to provide signal levels in your desired coverage area to capture the receiver of a mobile or portable radio.  Meaning, if you are wanting to cover X number of square miles and that can be done with an antenna at 40 feet of height and 10 watts, Don't set the repeater up to 50 watts.  It's not necessary and again, it's not good frequency management. 

So you now have a pair picked out.  What about a repeater?

A repeater is required to ID unless YOU and those under YOUR license are the only ones using the repeater.  The minute that other license holders are allowed to use the repeater, it needs to ID itself.  Now this can be done with a Raspberry Pi, an Arduino or some specific module for CW ID.  You have options.  You can use two mobile radios as a repeater with a cable between them and an ID board.  You are not required to have voice announcements, roger beeps or any of that.  So it can be a simple set of radios.  (Motorola CDM series work great and the 16 pin interface makes connecting them very easy).  Or you can buy a repeater that is a purpose built device.  There are a number of options. 

 

More to come.... stay tuned.

 

 

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The next bit is the duplexer.  And there are a number of options here as well.  The point of install is going to set the requirement for what gets used.

The little flat pack UHF duplexers are very usable on GMRS in certain instances.  Those are going to be the smaller installations on a relatively short town (under 100 feet) in an rural setting or maybe a suburban setting where there are not a lot of other repeaters near you.  These duplexers work on a frequency reject configuration where the input side rejects the output and vice versa.  There isn't a pass component to this style duplexer, which means that the specific frequency and a few kilohertz above and below it are blocked but EVERYTHING else is passed through.  This becomes a problem for installs where the antenna is receiving a number of other things, both UHF and elsewhere on the band and allowing that RF to get into the receiver of the repeater.  The reason this is a problem is the first amplifier in the radio receiver string can only handle so much signal before it gets swamped.  For a quiet area, it's not a big concern.  If you are at a tower site with many other transmitters then you will need a pass/ reject type of duplexer where the frequencies of interest (TX and RX) are the only frequencies that are passed through the duplexer and everything else gets rejected.

 

ANTENNAS and HEIGHT

Here's where the distance that the repeater is going to cover really gets set.  There are some folks that will tell you power level is everything.  I am here to say that's false.

I have a repeater system that I maintain for my employer that can be heard 60 miles from the transmitter site.  And it's turned down to 20 watts coming out of the repeaters.  The antenna height is over 500 feet however.  And it still talks farther than it can effectively hear.  Add to the 20 watts the fact it goes through an 8 port combiner and looses another 6 dB of signal level and is feeding 650 feet of cable (more loss) and it's only getting about 6 watts to the antenna connector. 

Point is that if you really want to cover a LOT of area, height is key to doing so.  But know that you are NOT gonna be able to run LMR 400 or 600 up a tower like that and have good results.  Cable loss is figured in dB per 100 feet or 100 meter lengths.  If you look up what cable you are using, it will have the numbers for the frequency range that you are operating on.  This is important on long runs.  Anything longer than 100 feet for UHF really should have 7/8 cable at a minimum in use. 

Getting to the antenna.

I have spoke to people that were looking at using some mail order antenna thing that you went to a hardware store and bought PVC pipe to build the antenna.  This might be ok for your home base station or repeater.  But I have built these types of antenna's and they doing hold up for very long.  Find an Andrew / CommScope or other commercial antenna and use that for a repeater.  You will have much better luck and will be happier when you are not needing to replace the antenna every 6 months because the wind broke it.

 

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Delete this comment if you're making this a series of posts.

Would it be a good idea to hook up radio equipment, high up on the tower right near the actual antenna, vs running 100+ feet of cabling? Then, run a fiber cable from that location down to equipment below to remote control it and such.

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8 hours ago, pcradio said:

Delete this comment if you're making this a series of posts.

Would it be a good idea to hook up radio equipment, high up on the tower right near the actual antenna, vs running 100+ feet of cabling? Then, run a fiber cable from that location down to equipment below to remote control it and such.

Thats basically how alot of the cellular stuff is run to be honest as well as the low power microwave stuff now. LMR has not made it to that point although I'm sure its coming. Issue with radio on the tower lets say in a box is repairs. It costs alot of money to put a climber on a tower. Most tower guys know nothing about radio but are more of a "plumber". Basically they would have to bring the box down to fix. Also no way to do a PM check on stuff on the tower. In the end a shelter is a better location for a repeater with the antenna line up the tower.

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On 9/29/2021 at 10:04 PM, WRKC935 said:

A repeater is required to ID unless YOU and those under YOUR license are the only ones using the repeater.  The minute that other license holders are allowed to use the repeater, it needs to ID itself. 

Can you double check this statement? According to this topic and some other sources on the internet, it doesn't sound like a repeater id is necessary as long as everyone using the repeater self identifies with their call sign.

 

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Repeaters are not required to ID. Many do as it satisfices the requirement of ID for the user. Many don't as they don't want folks to know a repeater is there. 

 

For my repeater that does ID I use tactile call signs vs dealing with my GMRS call. The repeater is sending it every 15 minutes. The repeaters that don't ID I need to ID. Any repeater cal sit on the air for years and as long as its not being used there is no requirement to send an ID. In commercial and public safety that is different.

 

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1 hour ago, DownEastNC said:

Can you double check this statement? According to this topic and some other sources on the internet, it doesn't sound like a repeater id is necessary as long as everyone using the repeater self identifies with their call sign.

See:

Quote

§ 95.1751 GMRS station identification.

Each GMRS station must be identified by transmission of its FCC-assigned call sign at the end of transmissions and at periodic intervals during transmissions except as provided in paragraph (c) of this section. A unit number may be included after the call sign in the identification.

(a) The GMRS station call sign must be transmitted:

(1) Following a single transmission or a series of transmissions; and,

(2) After 15 minutes and at least once every 15 minutes thereafter during a series of transmissions lasting more than 15 minutes.

(b) The call sign must be transmitted using voice in the English language or international Morse code telegraphy using an audible tone.

(c) Any GMRS repeater station is not required to transmit station identification if:

(1) It retransmits only communications from GMRS stations operating under authority of the individual license under which it operates; and,

(2) The GMRS stations whose communications are retransmitted are properly identified in accordance with this section.

I interpret "it retransmits only communications from GMRS stations operating under authority of the individual licensed under which it operates" as individuals authorized to use the repeater owner's license only (ie. authorized family members). Then for bullet number two, you can't guarantee that everyone using your repeater will identify properly especially if you turn it open to the licensed public, so it's best practice to have the machine ID on that merit alone.

The only time you're in the clear if the repeater doesn't identify is if it's a private, family-use-only repeater and everyone ID's.

Sauce: https://www.ecfr.gov/current/title-47/chapter-I/subchapter-D/part-95#95.1751

There was a comment a ways up about intentionally not having repeaters ID to keep them unknown - while I understand the sentiment, it's a bad idea in the sense that GMRS doesn't have a frequency coordination body. Since we're all supposed to play nice and not cause interference, self-coordination becomes more difficult if your machine is undetectable; I can't avoid a repeater if I have no way of knowing it's there. List it on myGMRS and have it beacon if you want to discourage other users from parking others on the same frequency, then use split tones or other mechanisms to lock it down to your use only, otherwise don't be surprised if someone shows up with their own repeater on the same frequency one day. The beacon can be less frequent than the 'active traffic' identifying requirement; even if you do it on the hour or every few hours it's enough to be noticed by someone monitoring for a free frequency pair.

Edited by JeepCrawler98
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I want to thank JeepCrawler98 for pointing out the ID requirements for a repeater.

If you are the ONLY licensed user and the repeater is closed to all others, and everyone uses YOUR call sign legally under the rules then it doesn't have to ID.

If anyone else uses it, it needs to ID.  And in truth, it's just easier to have it ID.  Now for those that don't want it to sit there banging away every 10 minutes with an ID, use a commercial repeater and allow the repeater to ID through the programming.  This will be at a set interval as long as the repeater is active.  Meaning that if no one is talking on it, it's doesn't ID.  That is within the regulations.  I have heard HAM repeaters that bang away every 9 minutes.  In fact I have one local to me that has two ID mechanisms in it.  Both are voice. They are set at 9 minutes and 8 minutes.   The 9 minute one is EVERY 9 minutes without fail.  The other one is active only.  But you can all but have a conversation with the dumb thing because it talks so much.  DON"T BE THE GUY WITH THE HAMMIE NONSENSE TALKING REPEATER on GMRS.  That is unless you really don't want other people to use the repeater.

 

 

ANTENNA LOCATION

So you have gathered a bunch of parts together and now you want to put your repeater on the air.  Question is where are you going to put it.  We discussed that antenna height is KEY to how far will it talk and hear.  If you put it on your garage roof, it's gonna talk a few miles but nothing crazy.  If you want to have the big dog, you have to have have a big tower. 

Now there is software that is online  called RADIOMOBILE that will plot coverage maps out for you based on the info you put in and maps that it pulls from the Internet that I have found to be reasonably accurate.  You key in all the info and it pops out a map.  And because it's computer based, and you are controlling it you can create maps with different antenna heights and locations that you can reference. 

I will tell you this now and save you the headache.  For the most part, if a tower is owned by one of the major tower companies, they are going to want at a minimum 1000 bucks a month for access to hang an antenna.  Will require you to hire an approved tower company to install the antenna.  You will probably be required to get your own electrical service and carry insurance as well.  Now there are exceptions to this as well.  I currently have the ability to put up all 8 repeater pairs via the antenna system I have.  I run a receive multi-coupler and a transmit combiner.  I am currently only hosting two of the 8 pairs on repeaters.  I can't say that I am the only person in the entire USA that would do this, but IF you need hosting in central Ohio, have a name brand repeater that is RACK MOUNT, and are willing to cover the bit of additional electric, I will host it on my tower.  That being said.  AGAIN, if YOU have this sort of setup, you should be willing to do the same in my opinion. 

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