I have a love/hate relationship with FRS/GMRS radios. They are inexpensive, and you can buy them practically anywhere. They are great for the kids to play with, and are very useful when camping, boating, hiking, or driving in a convoy with your friends. However, the range is short and the antennas are not replaceable. Nevertheless they work pretty well as long as everyone has the same brand of radio. But if you are trying to talk to people who have different a different brand of radio than yours, things can get a bit trickier.
The easiest way to make your radios talk to each other is to put them on the same channel, and turn off the privacy codes, or sub codes, or interference eliminator codes, or whatever your radio calls it. If you want to use a privacy code, first of all, know that they don’t give you any privacy. If you still want to use a so called privacy code, just pick one that’s less than 38 and you should be good to go. If that doesn’t work, keep reading.
FRS and GMRS radios use channel numbers as a substitute for the frequency. The frequencies are defined by the FCC and all the manufacturers seem to assign the same channel numbers to the same frequencies. Occasionally there is some confusion because the GMRS frequencies overlap with the FRS frequencies, i.e. GMRS channel 9 and FRS channel 1 are both on 462.5625 MHz. Some radios only do FRS, and some do FRS and GMRS. However, all the major manufacturers like Cobra, Midland, Motorola, and Uniden all use the same channel numbering scheme. If you put your radios on channel 8, they will all be utilizing 467.5625 MHz, as shown in this chart. Baofeng’s GMRS-V1 is the exception. Instead of numbering the channels like everyone else, they numbered them in increasing frequency order. The three columns on the left are how the FCC thinks about FRS and GMRS channels, and the two columns on the right are how radios present those frequencies to you as channels.
|Frequency||FRS Channel||GMRS Channel||radios||Channel|
|462.5625||FRS 1||GMRS 9||1||2|
|462.5875||FRS 2||GMRS 10||2||4|
|462.6125||FRS 3||GMRS 11||3||6|
|462.6375||FRS 4||GMRS 12||4||8|
|462.6625||FRS 5||GMRS 13||5||10|
|462.6875||FRS 6||GMRS 14||6||12|
|462.7125||FRS 7||GMRS 15||7||14|
|467.5500||GMRS 1 in||16|
|467.5750||GMRS 2 in||17|
|467.6000||GMRS 3 in||18|
|467.6250||GMRS 4 in||19|
|467.6500||GMRS 5 in||20|
|467.6750||GMRS 6 in||21|
|467.7000||GMRS 7 in||22|
|467.7250||GMRS 8 in||23|
If you have a FRS only radio, you will have 14 channels, and therefore won’t be able to talk to people on channel 18, which is GMRS only. Some radios are GMRS only, like the Midland MXT100. Instead of renumbering their channels, they just don’t have channels 8 through 14, because they are FRS only. So channel 20 on the MXT100 still works with everybody else’s channel 20. That’s pretty smart, and convenient.
You can mostly ignore the last 8 rows in that chart. Those are for GMRS repeaters. There are very few of these repeaters, and most GMRS radios can’t transmit on the repeater frequencies anyway.
I had to make some guesses about the Baofeng channels. The manual on their website page 34 and the manual they filed with the FCC page 32 don’t match. The above chart uses the numbers from the manual the FCC has.
What is Squelch Anyway?
So the channels just work no matter your brand of radio (except Baofeng). However, it’s not so smooth when it comes to the so called privacy codes. Motorola calls them interference eliminator codes. Uniden sometimes calls them sub codes. All these words are synonyms for either analog or digital squelch tones, and sometimes a synonym for both, which is unfortunate. If you are a ham radio operator, you probably know what squelch means. If the word squelch makes you think of that time you almost threw up and it went all the way to the back of your throat, don’t worry, it’s not that. Here’s a metaphor to explain.
Say you have 10 friends all in the same room at the same time. You assign two of your friends code 1, two friends code 2, two friends code 3, and so forth. Everyone starts whispering except one person, who starts talking. It’s easier for you to listen to the person talking, because they are louder than everyone else. That’s squelch. Now, everyone starts talking at the same time. If you are assigned to code 4, you try really hard to only listen to the other person who is assigned to code 4. That’s tone squelch. But if you really want to listen to the conversation going on between the two people assigned to code 5, you could do that too. In other words, squelch just tells your radio what to listen for, it has nothing to do with what is transmitted.
You can test this out for yourself if you have two FRS/GMRS radios. Set them both to the same channel, and then set one of them to use privacy code 5. Turn off the privacy code, or set it to 0, on the other radio. When you transmit on the radio with privacy code 5, you will still be able to hear the transmission on the radio with the privacy codes off. But when you transmit on the radio with the privacy codes off, the radio set to privacy code 5 won’t be able to hear. It’s not that the transmission wasn’t sent, it’s just that the radio is ignoring all transmissions without privacy code 5.
In real life, there are three basic types of squelch. The first is based on signal strength. The signal received by your radio has to be of a certain strength in order for your radio to decide it’s important enough for you to hear it. Turn the squelch down and you will hear all kinds of fuzzy signals. Turn the squelch up and you will hear only the stronger signals. Most FRS and GMRS radios don’t have this type of squelch setting.
The second type of squelch works by adding a low frequency tone to the transmission. The receiving radio ignores all signals that do not contain the specified tone. The tone is stripped out by the receiving radio before sending the signal to a speaker or headset. The real name for this method of transmission is Continuous Tone-Coded Squelch System or CTCSS. Most modern FRS and GMRS radios have CTCSS, but most of them don’t call it CTCSS.
Digital Coded Squelch or DCS is the final type, and it works by adding a sub-audible digital bitstream to the transmitted audio. The bitstream is used to transmit a code along with the audio. The radio ignores signals that do not include a bitstream with the specified code. Many FRS and GMRS radios, especially the higher end models, have DCS, but like CTCSS, most of these radios don’t call it DCS.
In an effort to avoid a long discussion like we just had about CTCSS and DCS, the FRS and GMRS radio manufacturers came up with different words to describe tone or digital squelch. Motorola uses “Private Line” or “PL” codes. They also use “interference eliminator codes”. Radio Shack (remember them?) used to call them “quiet codes”. Many manufacturers call them “privacy codes”. These consumer friendly terms refer to both CTCSS and DCS. Which makes everything confusing when trying to figure out how to make radios from different brands talk to each other. To make the description easier from here on out, we’ll just call them privacy codes. Just remember, they have nothing to do with privacy.
You don’t even have to use privacy codes. The easiest way to make your different brand radios talk to each other is to turn the privacy codes off.
Some radios don’t have privacy codes, like the Midland LXT110. That means you hear everyone on your channel, whether they use a privacy code or not. But it also means that nobody using a privacy code can hear you. They have to turn their codes off in order to listen to your transmission.
I love my Cobra HH450. It doesn’t have the FRS-only frequencies because it has a detachable antenna, and the FCC doesn’t allow detachable antennas on FRS radios. It has the GMRS frequencies and it transmits and receives on the marine VHF channels. It’s submersible and receives NOAA weather broadcasts. It’s a great radio to take to the lake. Even better, it doesn’t have “privacy codes”. It has a way to turn on CTCSS and set the tone, or you can turn on DCS and set the code.
CTCSS-based Privacy Codes
CTCSS adds a low frequency tone to the transmitted signal. By allowing a choice of the frequency of the tone, the radios make it so users on the same channel don’t have to listen to everyone else on that channel. There are more than 50 frequencies of tone that work for CTCSS, but 38 of them are commonly used on FRS or GMRS radios. The manufacturers assign a privacy code to each one of these 38 tone frequencies. And lucky for us, they mostly chose the same assignments.
On radios that have a way to specify CTCSS, like my Cobra HH450, you of course chose that squelch mode. On radios that just have a choice of privacy codes, like my Motorola TalkAbout MT351R, the first 38 privacy codes are CTCSS.
|Baofeng||Cherokee 465||Motorola Sport||Radio Shack|
Note that some radios use the tone frequency as the CTCSS setting, not a code number. The Jetstream JT270M works this way.
Some Baofeng radios use 177.3 Hz for CTCSS tone 33, some Baofeng radios use 177.8 Hz for CTCSS tone 33. Best to just avoid CTCSS tone 33 on the Baofeng.
DCS-based Privacy Codes
Digital Coded Squelch works by transmitting a digital bitstream with the audio. The bitstream is encoded with error correction and can accommodate 512 different squelch codes. These codes are typically represented as an octal (base 8) number. However, because of the way the codes are packed into the bitstream, there is a possibility of misalignment errors upon decoding. To reduce the potential for decoding errors, most manufacturers only use 83 of the 512 codes. However, some Midland radios and some Baofeng radios use more than that. In fact, the Baofeng and Jetstream radios can use inverted DCS codes (too complicated to explain here). Not sure why you would ever want or need that, so I’ve omitted them from the chart.
Many radios just have one set of numbered privacy codes, and you have to magically know where it switches from CTCSS to DCS. This is how my Motorola MT351R works. Privacy code 38 is CTCSS with a 250.3 Hz tone, privacy code 39 is DCS using code 023. The MT351R has 121 privacy codes, 38 CTCSS tones, and 83 DCS codes.
The DCS-based privacy codes have been implemented two different ways. Uniden and Motorola just keep the privacy code numbers going, and switch from CTCSS to DCS at code 39. Midland, Cobra, and Baofeng have a separate DCS mode, and the privacy codes start over at 1.
Baofeng can’t seem to agree on the setting for DCS code 99, so I’d suggest avoiding it. Pick 98 or 100 instead.
Feedback and Sources
I only have a couple of FRS/GMRS radios to test with, so most of this material has been pieced together using the online owners manuals provided by the various radio manufacturers. If you have any ability to verify these charts using your own equipment, I’d love to hear from you. Especially if you have a Baofeng GMRS-V1 radio. Email correspondence, suggestions, corrections, complaints, or gift cards to firstname.lastname@example.org.
This page was inspired by work originally done by Harold Melton KV5R. Unfortunatly, his original link no longer works and I can’t seem to find a replacement page on his site.
- RadioShack Frequencies
- Uniden GMR4040 Frequencies
- Uniden GMR645 Frequencies
- Uniden GMR4060 Frequencies
- Midland LXT110 Manual
- Midland GXT5000 Series Manual
- Midland GXT300/400 Series Manual
- Midland MXT100 Owners Manual
- Baofeng GMRS-V1 Manual as filed with the FCC.
- Motorola TLKR T8 Manual
- Jetstream JT270M Manual