FRS/GMRS Privacy Codes Demystified

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 (usually) 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.

This page will probably help you out if:

• You have GMRS or FRS radios from different manufacturers and you can't get them to talk to each other.
• You have a GMRS radio that sets CTCSS or DCS codes directly (i.e. Cobra HH450, Baofeng GMRS-V1, Baofeng GMRS-50X1) and you want to communicate with other GMRS/FRS radios that use privacy codes.
• You enjoy reading arcane radio related stuff.

The easiest way to make different manufacturer 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 them). If you want to use a privacy code, keep in mind that they don't give you any privacy. You can usually pick one that's less than 38 and it will work. My guess is that you already tried it and it didn't work, so you went a searching and found this page.

Channels and Frequencies

Almost all FRS and GMRS radios use channel numbers as a substitute for the frequency (the Baofeng GMRS-50X1 lets you set the frequency directly). The frequencies and channels are defined by the FCC. Note that while FRS and GMRS share the same frequencies and channels, FRS radios are limited to lower power output. If you are only communicating over short distances and there are many nearby FRS/GMRS radios, you may be better served to use channels 8-14. On the other hand, if you want to maximize the distance of your communications, you should choose channels 1-7 or 15-22.

Many handheld FRS/GMRS radios do not transmit at the maximum power limit. For example, a Motorola T600 has a maximum transmit power of 1.5 W. My Cobra HH450 can transmit on GMRS at 1 W, 2 W, or 3 W.

In September 2017 the FCC combined and standardized the FRS and GMRS frequencies, which codified the common practice used by most manufacturers. Most radios built before September 2017 use the modern channel frequencies in the chart above. Some older GMRS only radios, like the Midland MXT105, don't transmit on channels 8-14 because those channels were previously designated as FRS only. The good news is that most of those radios just omit those channels from their settings. Channel 20 on the MXT105 works with everybody else's channel 20.

The last 8 frequencies in the chart, the ones without channel designations, are for use as repeater input frequencies. Most GMRS radios are designed for simplex operation and can't transmit on these frequencies. Which mostly doesn't matter because there are very few GMRS repeaters out there.

What is Squelch Anyway?

GMRS/FRS channels mostly just work no matter who manufactured the radio. 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, 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 third 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.

Privacy Codes

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 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. On many radios you turn the privacy code off by setting it to 0.

Some radios don't have privacy codes, like the Midland LXT118. 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; the FCC doesn't allow detachable antennas on FRS radios. It has the pre-2017 GMRS channels 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. This approach works great for a ham operator like me, but may be overwhelming for many who purchase these radios. So how do I know which privacy code to use on my Motorola MT351R when I set a CTCSS frequency of 88.5 Hz on the Cobra?

CTCSS-based Privacy Codes

CTCSS works by adding a low frequency tone to the transmitted signal. Radios configured to use CTCSS filter out any signals that don't contain the designated low frequency tone. There are more than 50 tone frequencies that work for CTCSS, but only 38 of them are commonly used on FRS or GMRS radios. A few radios (like the Cobra HH450, Jetstream JT270M, Baofeng GMRS-50X1 and Baofeng GMRS-V1) allow you to set the tone frequency directly. For most radios the manufacturer represents the various tone frequencies with a "privacy code". Lucky for us, they mostly chose the same assignments. The following chart shows a map between the CTCSS frequencies and privacy codes. The "Common" column is used by most manufacturers, including:

• Cobra
• Midland
• Motorola
• Uniden
• Backcountry Access
• Rocky Talkie - versions sold after July 16th 2020

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 the Baofeng radios can use any DCS code. 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, Motorola, and Backcountry Access just keep the privacy code numbers going, and switch from CTCSS to DCS at code 39. Midland and Cobra have a separate DCS mode, and the privacy codes start over at 1.

In this chart the "Common" column is used by the following manufacturers radios:

• Backcountry Access
• Motorola
• Uniden
• Rocky Talkie - versions sold after July 16th 2020

Some Midland radios, like the T70 series, only have 83 DCS privacy codes. Others, like the MXT105, have 104. The first 83 are the same across all Midland radios, but if you pick code 99 on your MXT105, most other radios will have to disable privacy codes in order to hear you.

Hopefully this helps make sense of the sometimes confusing so-called privacy codes on FRS and GMRS radios. If your radio isn't listed here or if you can confirm or dispute any information on this page, I'd love to hear from you. Email correspondence, suggestions, corrections, or complaints to jared@k0tfu.org.

Feedback and Sources

This page was inspired by work originally done by Harold Melton KV5R. Unfortunately, his original link no longer works and I can't seem to find a replacement page on his site. However, his page is preserved by the The Wayback Machine.

I only have a couple of FRS/GMRS radios to test with and the original version of this article was mostly pieced together from owners manuals. Since then several people have written with additional information on new radios and tests with their own equipment. Thanks to everyone who had contributed.

I've collected all my data in this Google Sheet, including the simplified tables published in this post. I used Tableizer to create HTML tables because embedded Google Sheets look really terrible.

Contributors

• Fred E for confirming Baofeng GMRS-V1 CTCSS frequencies.
• Jared S for confirming Baofeng GMRS-V1 DCS and CTCSS interoperability with a Motorola T600 using these charts.
• David M for confirming the Midland X-Talker T290 matches the tables in this article.
• Tim W for the Wayback Machine link to Harold Melton's original page.
• Eric KI7WJP for providing verified Backcountry Access CTCSS and DCS codes.
• Tom B for confirming Retevis RB15 and Rockie Talkie codes and providing links to owners manuals.

Owners Manuals

• Backcountry Access Link 2.0 Manual which contains no useful information about their privacy codes, not even if they use CTCSS or DCS.

• Baofeng GMRS-V1 Manual
• Baofeng GMRS-50X1 Manual

• Cobra HH450 Dual Owners Manual
• Cobra ACXT645 Owner's Manual

• Jetstream JT270M Manual

• Midland T70 Series Manual
• Midland LXT118 Manual
• Midland GXT300/400 Series Manual
• Midland GXT5000 Series Manual
• Midland MXT105 Owner's Manual

• Motorola MT Series Users Guide which doesn't contain a CTCSS or DCS chart (boo).
• Motorola T600 Series User Manual
• Motorola TLKR T8 Manual which has Motorola's map of CTCSS tones and DCS codes to their "sub-codes"

• Retevis RB15 Manual
• Retevis RB15 CTCSS Blog Post
• Retevis RB15 DCS Blog Post

• Rocky Talkie

• Uniden GMR645 Manual
• Uniden GMR4040 Manual
• Uniden GMR4060 Manual

Other Sources

• FRS/GMRS Combined Channel Chart
• Personal Radio Service Reform
• RadioShack Frequencies