Explaining the Confusion of Frequencies and Channels with FRS & GMRS Radios
UPDATE : OCTOBER 2017 : New frequencies and rules have been set by the FCC. We explain the new FCC changes to FRS/GMRS services here, and list the new FRS/GMRS frequencies and rules here.
The rest of this article, below, remains helpful and relevant and you’ll still benefit from reading it, but the specific frequencies have changed.
It should be really simple to understand the different frequencies available for FRS and GMRS radios. The FCC publish two short lists, one of the 14 FRS frequencies, and the other of the 23 GMRS frequencies.
So what else do we need to say, except to copy those lists? Well, unfortunately, radio manufacturers have deliberately made it as complicated as possible to understand exactly what their radios do and don’t have, to the point of making some claims which are hard to describe as anything other than outright lies.
The fact that seven of the FRS frequencies are duplicated as seven of the GMRS frequencies doesn’t help, and the further fact that 16 of the GMRS frequencies are in the form of eight paired frequencies for repeater use makes it a bit more complicated still, and then add to the confusion the fact that there are no formal universally adopted numbers or names for the different frequencies, with different manufacturers numbering the frequencies differently, and you have a definite recipe for confusion.
Hence this article. 🙂
Channels and Frequencies
There is a technical difference between the concept of channels and frequencies. But in this article we are generally using the two terms interchangeably, so if you see us talking about a FRS channel in one place and a FRS frequency somewhere else, we are probably talking about the same concept. Feel free to skip on to the next section on privacy codes at this point.
But, for the more technically minded, the different channels that these radios operate on each take up one specific frequency. For example, the lowest frequency used is 462.5500 MHz, and the next lowest frequency used is 462.5625 MHz. We could consider these two frequencies as each representing a channel.
In theory, with the right equipment, you could use any frequency at all – 462.3456789 MHz or any other frequency that took your fancy. But for good and sensible reasons, the FCC has directed radio traffic onto specific frequencies. Think of this a bit like marking lanes on the freeway – traffic flows much more smoothly (and safely!) if there are clearly defined lanes on the freeway, and similarly, radio traffic flows best if there are clearly defined channels.
You know this already, possibly without realizing it. Think of tuning your AM or FM radio. There might be an FM station at 98.7 MHz but there isn’t another one at 98.75 MHz, is there. There might be an AM station at 880 kHz, but there’s never one at 883 kHz.
So we are referring to each of the officially assigned frequencies as a channel. Simple, isn’t it.
Now for the nuisance part. With many types of radio service, there is a unique channel number associated with each and every frequency that can be used. This is true of CB and of MURS radios – indeed, with MURS there are both channel numbers (1 – 3) and also two channel names (Blue and Green).
This is also usually true of a radio that only has FRS frequencies in it. Channel 1 is always the lowest frequency and channel 14 the highest frequency.
But, because of the overlap of frequencies, it is not true of GMRS radios and it is not true of combined FRS/GMRS radios – indeed, not all FRS/GMRS radios even have all 30 possible frequencies to start with. Generally a manufacturer will follow the same numbering plan for all their radios, but there’s every chance that the frequency associated with a given channel number on (for example) a Cobra radio might be difficult from the frequency associated with the same channel number on (for example) a Uniden radio.
Don’t worry, there’s a solution. But there’s a bit more to tell you before we get to the solution.
The Difference Between ‘Privacy Codes’ and Channels
This is where the manufacturers like to start playing games. The short answer – ignore the ‘feature’ entirely. The longer answer? Keep reading.
You can only have one transmission at a time on a channel – you know this already, probably. If you and your friends/family are wanting to have a discussion on a channel, then if someone else and their friends also want to communicate at the same time, they are either going to have to share the channel you are on, or else, switch to another channel.
Most of the time of course, people will switch to another channel. If they can’t find a free channel, well, then it might get a bit ugly. Depending on how polite everyone is, either they’ll share it nicely, or else some users will attempt to rudely broadcast over the top of other users and pretend they are not there.
So clearly, the more channels available to you, the better it will be in a case where there are lots of other people wanting to use their radios at the same time.
One more point, then we’ll come to privacy codes. You also know that when you transmit your message, anyone else, within range of your radio, and with their radio tuned to your frequency, will hear it. You can’t create any sort of privacy or blocking, short of ‘scrambling’ (aka encrypting) your transmission, and the problem about scrambling your transmission is that it is illegal. The FCC doesn’t allow you to do that.
Now for the privacy codes. Actually, they should be called ‘non-privacy’ codes, because they don’t give you any privacy at all. Quite the opposite. If you use a privacy code setting on your radios, everyone can still hear you, but you can no longer hear everyone else! Like we said, it is a non-privacy code. It is like putting hearing protectors on at a gun range.
So what are these (non)privacy codes? There are two different types – CTCSS and DCS. They both operate in similar ways, and what they do is they add a code or inaudible tone to your transmissions, and set your receiver to only play transmissions with that code/tone added to them.
This can – in very limited situations – be a good thing. Maybe you have two teams playing a match. Team A sets privacy code 32 to their radios, and team B sets privacy code 17 to their radios. As long as no-one cheated in either team and turned off their privacy code, then that would restrict messages. But the weakness is that the ‘privacy’ relies on the other person doing something, not on anything you can do.
There’s a very important thing to appreciate. Think again to team A with privacy code 32 and team B with privacy code 17, and all sharing the same channel. They can’t both be sending messages to their respective teams simultaneously. The channel can still only support one transmission at a time. The different privacy codes don’t create ‘sub-channels’ that can be used simultaneously.
This exposes another weakness of the concept. If you have a privacy code set, you won’t hear all the other users – those with no privacy code at all, and those with different privacy codes – on your channel, and unless you have a radio that won’t transmit on a channel that is already in use (this is a high-end feature seldom found on consumer radios) or unless you have a way to turn the privacy code off and check the channel is free before then turning it back on to transmit (yes, this is a hassle), you run the risk of transmitting at a time when someone else is already transmitting, and then the two of you will block/jam/interfere with each other, creating a confused mess for both people transmitting and anyone/everyone listening to them as well. You then get re-transmissions, and listeners transmitting saying ‘please repeat’ and what should have been simple and easy becomes complicated and extended. Yuck.
There are some technical reasons why these codes can be useful and helpful, but for ‘normal’ users such as us, these reasons probably don’t apply. Instead, privacy codes are dangerously unhelpful, while giving you no privacy at all. They can eliminate the number of distracting messages that come in over your radio from people you don’t need to hear from, but when you talk yourself, your signal can be heard by anyone (as long as they don’t have a different privacy code set on their radio).
We strongly recommend you do not use the privacy code features on your radios.
But the marketers of radios don’t necessarily explain the problems of privacy codes to you. Quite the opposite. They’ll offer them up as great benefits to you, and they’ll also play games. Instead of saying ‘This radio has 14 channels and 25 privacy codes’ they’ll say something like ‘this radio gives you 350 different channel options to choose from’ – what they’ve done is they’ve worked out all possible different combinations of privacy code settings and channel settings.
But your radio still only has however many channels, no matter how many privacy codes there might be.
Some companies go a slightly different route to try and make their radios seem better than the other guy’s radios. On the channel selector button they might have numbers from 1 – 50 (as is the case with some Midland radios). Now remember what we started off by saying – in total, there can never be more than 30 channels in a FRS/GMRS radio. The FCC does not allow that.
So how is it that Midland is saying ‘You should buy our radio, it is better than the Motorola radio because it has 50 channels instead of their 30 channels’? We asked Midland that question, and they never answered our email (shame on them). But some research showed that what Midland did is simply repeat some of the channels a second time, but this time with a privacy code setting as well. So, for example, maybe their channel 7 is identical to their channel 37, except for channel 7 normally defaulting to no privacy code, and channel 37 normally defaulting to having a privacy code. So suggesting they have 50 channels that could support 50 different users simultaneously is total nonsense.
Read our lips : There are 14 FRS frequencies and 23 GMRS frequencies. Seven of these are shared frequencies, so in total, there is a maximum possible of only and exactly 30 frequencies. Not 31. Not 32. And definitely not (are you listening, Midland) 50!
Per the official FCC website, here are the fourteen FRS channels.
Per the official FCC website, here are the 23 GMRS channels.
You don’t have to look too hard at these two lists to realize that seven of the channels are in both lists. The first seven of the FRS frequencies are shared with the 2nd, 4th, 6th, 8th, 10th, 12th and 14th of the GMRS frequencies.
If you’re good at seeing patterns in numbers, you might notice that the last eight GMRS channels are exactly 5 MHz higher than eight of the earlier GMRS channels. These create eight pairs of frequencies to be used with repeaters, with the frequency on your radio’s transmitter being the higher frequency and the frequency on your radio’s receiver being the lower frequency.
Most consumer radios do not support this type of split frequency operating mode and simply transmit and receive on the same frequency. You can use any of these repeater pairs for normal GMRS calling.
Mapping Channel Numbers to Frequencies
As we mentioned above in the section on the difference between frequencies and channels, there is sometimes confusion between the channel numbers used by a radio manufacturer and the frequencies they assign to those channels.
If you have two different radios, you need to carefully check and compare the frequencies associated with each channel number. This is always shown somewhere in the manual that comes with the radio.
We suggest you take a copy of our table here, and then locate each frequency on the left hand side, and write the corresponding channel number assigned to it by your radio in a column on the right hand side. That way, if you have multiple different makes/models of radios, you can then easily see ‘Ah yes, channel 6 on your radio is the same as channel 12 on mine’ or whatever else may be the case.
Note that we’ve numbered the repeater pairs (RX for repeater output, TX for repeater input), but this only matters if you’ve a repeater capable radio. Otherwise, ignore our numbering.
Some manufacturers have exploited the confusion that can possibly arise in the minds of non-technical prospective purchasers of their FRS/GMRS radios and have created fanciful claims of their radios having many more frequencies on it than it really truly has.
There are a maximum of 14 frequencies possible on FRS radios, and a maximum of 23 frequencies possible on a GMRS radio. Due to seven of these frequencies being combined FRS & GMRS, a dual purpose radio can have a maximum of 30 frequencies, and may have less.
Because of the way the frequencies have been intermixed between FRS and GMRS, different manufacturers number the frequencies differently on their channel selectors. You’ll need to carefully match their numbers with the frequencies they relate to, and using the table above can help you ‘translate’ between the numbers/frequencies on one radio with the different numbers and frequencies they are assigned to on another radio.
This article is one of a series of articles on using radios at your retreat (and anywhere else too of course). Click to see our full section of articles on communications topics.