GMRS Radios, Repeaters, Licensing and Operating


BeCERTAINN facilitates radio communication between neighborhoods across Berkeley and beyond. We practice regularly with a weekly on-air net, Tuesday evenings at 7:30pm, on GMRS channel 22 R (repeater settings required). Anyone with a GMRS radio can listen, and anyone with a repeater capable GMRS radio is welcome and encouraged to check-in to the net.

The General Mobile Radio Service (GMRS) is a set of frequencies used by many consumer oriented handheld radios (walkie-talkies), and requires a license to operate legally. The license is easy to get from the FCC, and costs $70 for 10 years. Find details on licensing below. Background information on GMRS can be found on the FCC website and Wikipedia.

BeCERTAINN participants use GMRS radios with repeater capabilities, including some of the higher-end consumer GMRS radios and a number of re-purposed commercial radios which we can reprogram for GMRS use. See below for more information on which radios work with the BeCERTAINN repeater and how to set them up for use with the repeater.

About Repeaters

A repeater listens on one frequency and re-transmits what it hears on another frequency, usually at higher power through an elevated antenna. This allows anyone who can reach the repeater with their radio to talk to anyone else who can reach the repeater, even if they are too far apart to communicate with each-other directly. Using a repeater like this requires a radio to operate with "split frequencies", one to receive (repeater output) and a different one to transmit (repeater input). Many repeaters also use a "PL Tone" to reduce re-transmission of unintended signals.

To work with the BeCERTAINN repeater, radios should be set up as follows:

  • Receive Frequency: 462.725 MHz (repeater output)
  • Transmit Frequency: 467.725 MHz (repeater input)
  • Transmit PL Tone: 88.5 Hz (required for repeater operation)
  • Receive PL Tone: 88.5 Hz (optional)

The backup repeater is the same as above, except the Receive PL Tone is 71.9 Hz (optional)

If both repeaters are down, we plan to use 462.725 MHz simplex (GMRS channel 22 on some radios).

Repeater Details

(click to expand for more)

About Split Frequencies

In basic "simplex" communications (direct radio to radio), the same frequency is used for transmit and receive, meaning that the radios listen on the frequency, and when the operator pushes the PTT (Push To Talk) button, they transmit on that same frequency. On the other hand, typical repeater communications use two frequencies, aka: "split frequency operation". One frequency is the repeater input and the other is the repeater output. The radios using the repeater will receive (listen) on the repeater output frequency, and when the operator pushes the PTT button, they will automatically switch to transmit on the repeater input frequency. This way, the transmitting radio is on one frequency into the repeater, and then the repeater re-transmits on the other frequency to the receiving radio. Without these split frequencies the repeater would not be able to receive and re-transmit at the same time.

[Note that there are such things as "simplex repeaters", which work by listening on one frequency, recording the message, and then after the transmission is finished, re-transmitting it on the same frequency. That's less common, and not what the BeCERTAINN repeater does.]

The BeCERTAINN repeater receives on 462.725 MHz and transmits on 467.725 MHz, meaning that radios using the repeater will flip those around to transmit on 462.725 MHz and receive on 467.725 MHz. Many (but not all) GMRS Radios denote this as Channel 22R. Note that 462.725 MHz (our input frequency) is also a GMRS Simplex frequency, denoted on many radios as Channel 22 (without the "R"). Because of this, there are often simplex signals on that frequency, which are not intended for the repeater, so how do we keep the repeater from re-transmitting those signals? That's where PL tones come in.

About PL Tones / CTCSS Tones

Most radios can include a sub-audible "tone" on their transmissions, and can be set up to only receive signals with a tone. This allows us to set up the repeater to only re-transmit signals that include a specific tone, reducing interference from unintended signals on the same frequency. The repeater can also include a tone on its output, allowing receiving radios to filter out other signals that don't include the tone.

CTCSS stands for "Continuous Tone-Coded Squelch System", and is commonly known as "PL Tones" from the Motorola trademark "Private Line". That's a misnomer, as discussed below. CTCSS tones are "sub-audible", since they are below the range of human hearing, usually between 67 and 257 Hz. Even though we can't hear them, the repeater and radio can, and can open the squelch (produce audio output) when the tone is present. Again, this allows to repeater to only repeat signals with the tone, and receiving radios to only hear signals that include the tone.

The BeCERTAINN repeater uses a tone of 88.5 Hz for both input and output, meaning that radios using the repeater are required to transmit that tone, and can optionally filter for that tone on receive. Note that the backup repeater uses a different tone (71.9 Hz) on its output, so if the backup repeater is running, and your radio is set to receive the 88.5 Hz tone, then you won't hear the repeater and will need to switch receive tones, or set your radio to not filter for tone on receive. Also note that the repeater does not include tone when it transmits its occasional ID in morse code. If you hear the ID, then your radio is likely not set up to filter on receive tone.

Understanding PL tones can be confusing since they are often marketed as "private line" or "privacy codes". But adding a tone to your transmission doesn't actually prevent others from hearing your transmission. Rather, it allows others to filter out other signals if they wish to, and only hear your signal and others that include the same tone. Anyone can set up their radio to not filter for tones on receive (often code #0), in which case they will hear ALL signals on that frequency, regardless of whether or not they include a tone.

GMRS Licensing

To legally use a GMRS radio, you must obtain a GMRS license from the FCC. This is a relatively quick and easy process, It does NOT require taking a test like for Amateur Radio (Ham) licenses. A GMRS license costs $70, is good for 10 years, and covers the license holder and their immediate family. You can apply by filling out paper forms, or apply online via the FCC Universal License System (ULS).

Steps to apply online:

  1. Register for an FCC Registration Number (FRN), if you don't already have one
      1. Start here:
      2. Go to New User Registration and follow the instructions
      3. Note your FRN and password
  2. Apply for a GMRS License
      1. Go to the FCC ULS here:
      2. Log in with your FRN
      3. Click "Apply for a New License" at the top of the left-hand menu
      4. Select GMRS License (service code ZA, bottom of the list)
      5. Fill out the application as instructed
      6. Certify your information and sign your application
      7. Pay the license fee
  3. Get your assigned GMRS callsign
      1. After your application has been granted (usually within a few business days), you can log back in to get your callsign and download a copy of your license.
      2. Write down your callsign on or near your radio (and in phonetics), to help you remember.

Question: This license sounds like a hassle, what am I getting over license-free radios?

Answer: Increased Power, Better Antennas, Repeater Capabilities, connection to other neighborhood groups, etc!

For more information, see the FCC's GMS overview:

Choosing a Radio

In order to participate in BeCERTAINN, you need a GMRS radio capable of working with the repeater. Many basic GMRS radios, like walkie-talkies from the sporting goods store, can use the GMRS simplex frequencies, but cannot be set up to use a repeater. A few of the higher-end walkie-talkies can use repeaters, and there are a few full-featured GMRS radios available new, each with some pros and cons. Many BeCERTAINN participants use re-purposed commercial radios that have been programmed for the GMRS channels and the BeCERTAINN repeater, mostly because they can be cheaper and better quality. To do so legally, you need a radio which 1.) is capable of transmitting on the correct frequencies, 2.) can be programmed with the repeater settings (frequency split and tone), and 3.) is "type accepted" by the FCC for use on the GMRS frequencies (ideally Part 95 type-accepted, though some readings of the rules interpret Part 90 type-accepted as sufficient).

Recommended Radios:

If your group is just getting started, you may be able to get a Motorola Radius P1225 from BeCERTAINN. These are good quality, simple to use, commercial handheld radios, which BeCERTAINN volunteers refurbish and program for GMRS use on our repeater. Please contact BeCERTAINN to inquire about availability of these radios for borrowing or purchase by CERT teams or neighborhood groups.

If you're looking to buy a solid GMRS radio that's simple to use, good quality and FCC certified, we recommend the Wouxun KG-805G. It is a newly released, professional quality handheld GMRS radio, available for about $80, here and here (current March 2020).

For more details, see this list of radios which have been tested with, or are expected to work with the BeCERTAINN repeater. Please note which radios are FCC certified (type accepted) for GMRS.

Setting up your Radio

The basic steps in setting up your radio are listed below. The details will depend on which make & model radio you have.

  • Familiarize yourself with the basic functions of your radio, including how to turn the power on & off, how to adjust the channel and volume, how to operate the Push To Talk (PTT) button. Note that some radios have two PTT buttons, one for high power, one for low. Some radios have additional controls to learn about, including the lock button, squelch control and the settings menu.
  • Set your channel to GMRS Channel 22 (on most radios), or whichever channel uses the frequency of 462.725 MHz.
  • Enable the repeater function on your radio, so that it will use split frequencies to still receive on 462.725 MHz, but transmit on 467.725 MHz (5 MHz higher). This often requires using the settings menu.
  • Enable the 88.5 Hz PL Tone or CTCSS Tone (sometimes referred to as privacy or security settings). This is required to be used on transmit to trigger the repeater, and can optionally be used on receive to filter out signals from stations other than the repeater.
  • If applicable, save your settings in a new channel or memory slot on your radio, so you can bring them back quickly when you need them.
  • If your radio can be programmed with multiple memory entries, consider having one for the repeater with TX and RX tones, one for the repeater with just TX tone, one for the backup repeater's tones, and one for Ch 22 Simplex.
  • Keep your batteries healthy and charged. If you plan to store your radio without using it for more than a few weeks, consider the health of the batteries. If your radio has alkaline batteries, remove them so that they don't leak in the radio. Note that some radios loose their programming or memories if stored without batteries for a certain time. If your radio has rechargeable batteries, find out whether it can be left on the charger longterm, or if it's best stored with the battery removed. Some radios still draw a little current from the battery even when turned off, so learn how to avoid having a dead battery when you need it in an emergency. And always have spare batteries available.

For more help setting up and maintaining your radio, refer to your radio's manual or ask your friendly neighbors on the mailing list.

Good Operating Practices

Some etiquette and best practices for operating professionally and effectively:

  • Learn your call sign and how to say it in phonetics. Try to memorize your call sign or write it on the front of your radio (masking tape and a sharpie works), so that you can provide it when operating or asked for it. Find the ITU/NATO phonetic alphabet here and here.
  • Identify with your call sign at least every 15 minutes during a conversation, and at the end of your conversation (this is a legal requirement of your GMRS license). It's not necessary to say your call sign in every transmission. In a real emergency, you may also want to use a Tactical ID (neighborhood or CERT group name) at the beginning of each transmission. More info on the Emergencies page.
  • Don't talk with codes, plain English is best. Please avoid Q-codes, 10-codes, "cb lingo" or other codes.
  • Keep your transmissions brief. Good operators have conversations that are short, sweet and to the point.
  • Give others a chance to transmit, speak or identify themselves. Considerate operators occasionally pause to give others a chance to say something, especially when using long transmissions, or having rapid back and forth conversations. Especially during emergencies, leave gaps for someone with emergency traffic to jump in. If necessary, give others a chance to sign out with their call sign after replying to them.
  • GMRS is for use by individuals and their friends and family, for non-commercial purposes (with some businesses users grandfathered in).

Radio Performance

If your handheld radio is having trouble hearing or or being heard by another station or the repeater, here are some things you can try to improve the chances of getting your message through. These may help in marginal situations, but won't help in all cases, like if you're really too far away, or significantly blocked by terrain.

  • Clear view - go to a place with that minimizes the hills, terrain, buildings and trees between you and the other station or repeater.
  • Higher elevation - get to as high a spot as practical, without compromising safety.
  • Hold the radio straight, with the antenna perpendicular to the direction you want the signal to go, and with the radio between you and the station you want to reach. Usually this means having the antenna straight up and down, so the strongest part of the signal goes out horizontally in front of you.
  • Hold the radio about 3 to 10 inches in front of your mouth, close enough that the microphone can hear you well, without overloading it, nor blowing directly on it. Talk across the mic, rather than directly into it. Avoid noisy environments if possible.
  • Hold the radio with one hand and don't touch the antenna. Most handheld radios come with relatively poor antennas, where your hand and body help provide a bit of "grounding" for the antenna, so they sometimes work better when you're holding them normally vs having them in a pouch or on a table.
  • Upgrade your antenna - You can significantly improve the performance of many handheld radios by replacing the stock "rubber duck" type antenna with a better (usually higher gain) antenna, which can often be purchased for between $15 and $40. Be sure to get an antenna that's tuned for the GMRS frequencies (between 462 and 468 MHz, where most UHF "commercial band" antennas will work), and the correct connector for your radio (beware of SMA vs reverse-SMA).
  • If you still have frequent trouble checking in to the net or otherwise using your radio from the places where you expect to need it in a disaster, then you can consider upgrading to a "mobile" style radio with higher output power and an external antenna & power source. You can also reach out on the mailing list to ask for help from other participants.