Ham Radio Repeaters for Off Roading
As an off roader and avid 4×4 adventurer, repeaters are a massive part of why I got interested in ham radio to begin with. Repeaters are this magical machine that takes your radio transmissions, and repeats them to a wider range and bigger audience. If you get stuck somewhere in America, there is a very high chance that you will be within range of a repeater.
The nice thing about that, is, usually, people are monitoring repeaters… especially in the mornings and evening times. So, if you find yourself in a predicament while playing in your 4×4, if you can hit a repeater, you will most likely get help. Sometimes, you may need to leave the vehicle and hike up to the top of a ridge, but that beats having to hike all the way back to civilization.
What is a Ham Radio Repeater?
A repeater is an automatic controlled radio station that automatically takes an incoming signal and simultaneously repeats it out to a wide area. What makes repeaters work great, is they are usually situated at high altitudes, on mountains or ridges, and run higher power than your average handheld or even mobile ham radios. Thus, they effectively make your signal reach far further than your handheld or mobile ham radios probably can by themselves.
Depending on the terrain, it is not uncommon to have repeaters get signals out over 200 miles away. Repeaters are the main reason that most backwoods adventurists get into ham radio. If you can have your signal hit a repeater, chances are, you will be able to find help for whatever problems you find yourself in while hiking the Pacific Crest Trail, by yourself, in a snow storm.
In order for repeaters to receive a signal and transmit a signal simultaneously, they have to “listen” and “talk” on two different frequencies. The frequency that you will HEAR a repeater on is regarded as the repeater’s “home” or “transmit” frequency. This is where you will find the repeater in repeater listings and directories. This “home” or “transmit” frequency will be the frequency that the repeater transmits on, and you will LISTEN to it on.
A repeater’s listening frequency will be what YOU will transmit on to talk to IT. Luckily, the difference between a repeater’s listening and transmitting frequencies has been standardized for the United States (which is coordinated by your local Frequency Coordinator). This difference in the 2 frequencies is referred to as a repeater’s “split” or “offset“.
For the 2meter band (140 MHz frequencies), the standardized split or “offset” is .6 MHz or 600 KHz. Most programming software and repeater information sources will list it as .6 MHz, but the Tech License Exam likes to list it as 600 KHz. For the 70cm band (440 MHz frequencies), the standardized split/offset is 5 MHz. The offset can then go one of two directions… positive 5 MHz or negative 5 MHz, from the repeater’s reference frequency (its transmitting frequency). This positive or negative shift is called the “split direction” or “split direction“.
Are you still with us??? What we have gone over so far is the hardest part of conceptualizing how a repeater works. If you understand the above, then you are doing great. If you don’t understand the above, then don’t hurt yourself trying to understand it. We will go over some examples below that will help visualize it.
Along with having the correct split and split direction, almost all repeaters will be protected by a sub-audible tone called a CTCSS (Continuous Tone Coded Squelch System), or DCS (Digitally Coded Squelch). Most repeaters will use CTCSS tones nowadays. Without this sub-audible tone, the repeater will not pick up and re-transmit your signals. Thus ensuring that only communications that are supposed to go into the repeater, actually make it in and get repeated out. This CTCSS tone is also referred to as a “PL” tone in most repeater listings and directories.
So, in order to successfully talk on a repeater, you need to know its:
a) Reference Frequency
c) Offset Direction
d) PL Tone
In the above picture, we see that the repeater’s transmitting frequency is 145.330, it has a negative .6 MHz offset for its receiving frequency, and it requires a 131.8 PL Tone.
So, 145.330 MHz is what you would tune to in order to listen to the repeater. In order to talk to the repeater, you would need to tune to 144.730 MHz (which is 145.330 plus the negative offset of .6 MHz).
It can be a huge pain and time suck to try and find repeaters in the areas that you are going to be adventuring in. To make life easier, My Off Road Radio has a collection of geographical repeater databases that you can purchase for your area. You receive a spreadsheet and reference booklet of up to 100 frequencies for just $29.99. We can even connect to your computer from anywhere in the country, and upload the programming for you into your radio. To see more info, head to the Radio Programming section of the website.
Some hardwired mobile radios have a “crossband repeat” function that turns your vehicle’s mobile radio into a mobile repeater. This works really well if you want to go for a day hike, and park the car in a spot where it can reach a repeater. You then take a handheld radio with you on your hike and talk to your car, which then repeats your signal to the repeater, which then repeats your signal out to whoever is listening.
Doing this just gives you another layer of safety to ensure that wherever you go hiking, even if you get down into a canyon, that, if you can still hit your car, your car can hit the repeater.
EchoLink and IRLP
With how grand the internet is, a lot of repeaters are being linked together via the internet. This means, you can access a lot of repeaters directly from your house, or even your cell phone. The two main systems for doing this are IRLP (Internet Radio Linking Project), and EchoLink. Which are really handy systems to have.
Using EchoLink allows you to be camping in The Rubicon, and talk to the Rubicon’s repeater system. Your family could be vacationing in New York, and they could get on EchoLink and connect to the Rubicon’s repeater via the internet. You then get to have a nice chat with your family. And you don’t need a cell signal to do so.
Check out our article on How To Setup And Use EchoLink for more info!
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