Updated 2023 01 20 – off the shelf repeaters, OPSEC, COMSEC
In my prior articles on the General Mobile Radio Service (GMRS), I talk about the rules and also how to get a GMRS license. I wrote those article prior to the FCC dropping the fee to $35. Remember that one GMRS license covers everyone in your household. If multiple people are using your license remember that each needs to identify periodically with the GMRS call sign then add some designator, i.e., “unit 1” for each person.
In this article I’m going to talk more about using GMRS as part of your communications plan.
Bear in mind this project is going to cost you around $2,000. If you do not have a very good location for your repeater, not just your roof, then you are only going to get the same coverage as a simplex radio. If you are not going to get 20 or more miles coverage this project isn’t probably worth it.
GMRS repeaters can be set up by anyone with a GMRS license. You can find used equipment fairly cheaply on eBay and other sites – these are a couple of places I’ve found for new repeaters
https://www.bridgecomsystems.com/search?type=article%2Cpage%2Cproduct&q=gmrs+repeater
https://www.retevissolutions.com/gmrs-repeater
https://shop.mygmrs.com/collections/repeaters-and-accessories
Motorola and Vertex also makes GMRS repeaters and I’ve found them on eBay.
I’ve seen articles using hand held radios to make a repeater. The problem with this is that hand helds are designed on an 80/20 or even 90/10 ratio of receive to transmit. They do not have a heat sink to dissipate the heat generated in transmit mode. A repeater could be transmitting for an extended time and a hand held will burn up quickly.
You will need an antenna, and a good antenna is one of the most important components. You will also need a duplexer – this allows you to run a single antenna for transmit and receive. If you can’t find a duplexer you can use two antennas, with the transmit above the receive, this limits interference because the antennas transmit radially, not up and down.
Bottom line, if you don’t have a good high location it is probably not worth your investment.
Off the shelf repeaters
I’ve been seeing a lot of adds for ‘repeaters in a box.’ Of course you know after you discuss something on social media you get slammed with ads 🙂 These boxes are usually, from the ones I’ve seen from Midland and Retevis and 10 watts and cost around $400. Compare this to a 50 watt BTECH GMRS radio that costs about $210. A transmission using 50 watt radio on simplex is going to travel further than a 10 watt signal. Again this comes back to location, if you have a significant location then their might be a difference.
Your Comms Plan
You can load all the GMRS simplex (direct) frequencies into your radios and use them on a rotating basis. However, you should also search for GMRS repeaters in your area of operations, that includes where you live, work, school and other places you frequent regularly. Go to mygmrs.com and create an account, an account will let you see the repeater pl tones where they are public but also allow you to request access from a repeater owner.
In some cases the repeater owner might list an estimate of the coverage range. This is only an estimate because it will vary based on the terrain. Cover will also depend on whether you are using a hand-held or mobile radio and the antenna you are using. If you have a base radio (mobile with a power supply) with an antenna on a roof or a pole you are going to get considerably more coverage.
When you have identified possible repeaters you need to program them into your radio and then test from each place you might need to use it. You will then have a matrix of repeater and coverage and can add those into your plan.
If you find yourself regularly using a repeater it would be a good neighbor to offer to make a contribution to the repeater owner.
You should look at GMRS as being a step to getting your ham license. You can use a GMRS simplex channel to teach your children good radio practice prior to letting them use a repeater.
Some GMRS repeaters are linked to others. Some also conduct regular nets.
OPSEC & COMSEC
One thing to consider is operations and communications security. In a normal day to day situation, i.e., blue sky, you are not normally worried about someone direction finding your location or repeater. However in a gray or even black sky you don’t want to give away your location.
Transmitting simplex will provide someone the ability to DF your signal fairly easily. If you are using a repeater the stronger signal is usually going to be the repeater and unless the DF’er knows to listen to a repeater input it might not be as easy to locate you. Also, with a repeater not at your primary location you could throw them off course. In a gray or black sky even you want to use the lowest amount of power needed to communicate and keep your transmissions short. For more on OPSEC and COMSEC see the articles under Book of Knowledge and Intelligence.