How To...
GMRS
- What is GMRS?
- What is FRS?
- FCC Licensing
- Channels and Frequencies
- Tones and Codes
- Repeaters
1. What is GMRS?
- GMRS is an acronym for General Mobile Radio Service.
- The General Mobile Radio Service is a land-mobile radio service used
for short-distance two-way communication.
- GMRS uses channelized frequencies in the UHF (Ultra High Frequency)
band.
- GMRS is intended for use by adult individuals who possess a valid
FCC license.
- GMRS radios can communicate with FRS radios using shared channels 1
through 22.
- GMRS radios may also communicate using repeaters on channels 15R
through 22R.
- GMRS radios can transmit at higher power levels than FRS radios (up
to 50 watts).
- GMRS radios may use removable and/or external antennas.
- See also:
FCC - General Mobile Radio Service.
2. What is FRS?
- FRS is an acronym for Family Radio
Service.
- This personal radio service operates using the same
channelized frequencies as GMRS.
- FRS is free for public use and does not require a license.
- FRS radios can communicate with GMRS radios using shared
channels 1 through 22.
- FRS radios do not have the ability to communicate via repeaters.
- FRS radios are restricted to lower transmit power levels
than GMRS radios (2 watts maximum).
- FRS radios must use non-removable fixed antennas.
- See also:
FCC - Family Radio Service.
3. FCC Licensing
4. Channels and Frequencies
- Simplex
- GMRS and FRS radios share channels 1 through 22.
- Channels 1 through 22 operate in Simplex Mode (single frequency).
- Each radio transmits (Tx) and receives (Rx) using the assigned
channel frequency:
|
Channel
|
Frequency (MHz)
|
Max Power (Watts) |
Bandwidth (kHz) |
Description |
| Receive |
Transmit |
FRS |
GMRS |
FRS |
GMRS |
| 1 |
462.5625 |
462.5625 |
2 |
5 |
12.5 |
20 |
GMRS
Interstitial 1 |
| 2 |
462.5875 |
462.5875 |
2 |
5 |
12.5 |
20 |
GMRS
Interstitial 2 |
| 3 |
462.6125 |
462.6125 |
2 |
5 |
12.5 |
20 |
GMRS
Interstitial 3 |
| 4 |
462.6375 |
462.6375 |
2 |
5 |
12.5 |
20 |
GMRS
Interstitial 4 |
| 5 |
462.6625 |
462.6625 |
2 |
5 |
12.5 |
20 |
GMRS
Interstitial 5 |
| 6 |
462.6875 |
462.6875 |
2 |
5 |
12.5 |
20 |
GMRS
Interstitial 6 |
| 7 |
462.7125 |
462.7125 |
2 |
5 |
12.5 |
20 |
GMRS
Interstitial 7 |
| 8 |
467.5625 |
467.5625 |
½ |
½ |
12.5 |
12.5 |
GMRS Primary 1 |
| 9 |
467.5875 |
467.5875 |
½ |
½ |
12.5 |
12.5 |
GMRS Primary 2 |
| 10 |
467.6125 |
467.6125 |
½ |
½ |
12.5 |
12.5 |
GMRS Primary 3 |
| 11 |
467.6375 |
467.6375 |
½ |
½ |
12.5 |
12.5 |
GMRS Primary 4 |
| 12 |
467.6625 |
467.6625 |
½ |
½ |
12.5 |
12.5 |
GMRS Primary 5 |
| 13 |
467.6875 |
467.6875 |
½ |
½ |
12.5 |
12.5 |
GMRS Primary 6 |
| 14 |
467.7125 |
467.7125 |
½ |
½ |
12.5 |
12.5 |
GMRS Primary 7 |
| 15 |
462.5500 |
462.5500 |
2 |
50 |
12.5 |
20 |
GMRS Primary 8 |
| 16 |
462.5750 |
462.5750 |
2 |
50 |
12.5 |
20 |
GMRS Primary 9 |
| 17 |
462.6000 |
462.6000 |
2 |
50 |
12.5 |
20 |
GMRS Primary
10 |
| 18 |
462.6250 |
462.6250 |
2 |
50 |
12.5 |
20 |
GMRS Primary
11 |
| 19 |
462.6500 |
462.6500 |
2 |
50 |
12.5 |
20 |
GMRS Primary
12 |
| 20 |
462.6750 |
462.6750 |
2 |
50 |
12.5 |
20 |
GMRS Primary
13 |
| 21 |
462.7000 |
462.7000 |
2 |
50 |
12.5 |
20 |
GMRS Primary
14 |
| 22 |
462.7250 |
462.7250 |
2 |
50 |
12.5 |
20 |
GMRS Primary
15 |
- Duplex
- GMRS radios have access to 8 additional repeater channels.
- Channels 15R through 22R operate in Duplex
Mode (dual frequency).
- GMRS repeater channels receive (Rx) using the
same frequencies assigned to channels 15 through 22.
- GMRS repeater channels transmit (Tx) using a
frequency 'offset' or 'shift' of 5 Mhz greater than the receive frequency:
|
Channel
|
Frequency (MHz)
|
Max Power (Watts) |
Bandwidth (kHz) |
Description |
| Receive |
Transmit |
| 15R |
462.5500 |
467.5500 |
50 |
20 |
GMRS Repeater
1 |
| 16R |
462.5750 |
467.5750 |
50 |
20 |
GMRS Repeater
2 |
| 17R |
462.6000 |
467.6000 |
50 |
20 |
GMRS Repeater
3 |
| 18R |
462.6250 |
467.6250 |
50 |
20 |
GMRS Repeater
4 |
| 19R |
462.6500 |
467.6500 |
50 |
20 |
GMRS Repeater
5 |
| 20R |
462.6750 |
467.6750 |
50 |
20 |
GMRS Repeater
6 |
| 21R |
462.7000 |
467.7000 |
50 |
20 |
GMRS Repeater
7 |
| 22R |
462.7250 |
467.7250 |
50 |
20 |
GMRS Repeater
8 |
5. Tones and Codes
- CTCSS
- CTCSS is an acronym for Continuous Tone Controlled Squelch System.
- This system encodes a user configured sub-audible squelch tone
into the radios audio transmission.
- Squelch tones allow you hear only the
conversations you want to hear by ignoring all channel activity from
radios not using the same tone.
- When using CTCSS tones, only radios on the same channel using
the same CTCSS tone will hear each other.
- Squelch tones do not make your conversation private (radios not
using CTCSS tones can still hear your conversation).
- CTCSS is not interoperable with radios
utilizing DCS squelching.
- DCS
- DCS is an acronym for Digital Coded Squelch (also known as
CDCSS, or Continuous Digital Coded Squelch System).
- Digital Coded
Squelch is an extension of the Continuous Tone Controlled Squelch
System.
- DCS provides additional squelch
codes to improve filtering of your conversation from outside parties
using the same channel.
- DCS codes
allow you hear only the conversations you want to hear by ignoring
all channel activity from radios not using the same code.
-
When using DCS codes, only radios on the same channel using the same
DCS code will hear each other.
- Squelch
codes do not make your conversation private (radios not using DCS
codes can still hear your conversation).
- DCS is not
interoperable with radios utilizing CTCSS squelching.
- Application
- Simplex
- GMRS radios operating on channels 1 through 22 transmit and
receive over the same frequency.
- Configuring a CTCSS tone or DCS code for these channels will
affect both transmit and receive operation.
-
Radios on the same channel using
the same tone/code will only hear each other.
- Radios monitoring the same channel with no tones/codes enabled
will hear all conversations.
- Duplex
- GMRS radios operating on channels 15R through 22R transmit and
receive on different frequencies.
- Radios allowing only a single tone/code to be
configured for each channel will have limited functionality.
-
Only radios allowing individual Tx/Rx tones/codes to be
configured for each channel can access split-tone repeaters.
-
Radios monitoring the same channel with no tones/codes enabled
will hear all conversations.
6. Repeaters
- Definition
- A repeater is an autonomous GMRS radio that transmits on one frequency what it receives on another frequency.
- Purpose
- The primary purpose of a GMRS repeater is to extend the operational range for GMRS radios that are
within range.
- Location
- GMRS repeaters can be found in a neighbors
back yard, at your local fire station, a church, or the top of a nearby hill
or mountain.
- Repeaters operating at higher elevations will provide
better range than those located at lower elevations.
- Remember, when
it comes to radio range, 'height is might.'
- Operation
- GMRS repeaters can be configured to operate on GMRS channels 15R through 22R.
- Channels 15R through 22R operate in Duplex Mode (dual frequency).
- To use a GMRS repeater, your radio must receive on one frequency and transmit on another.
- The radio receive frequency must match the repeater transmit frequency.
- The radio transmit frequency must match the repeater receive frequency.
- GMRS repeaters may use tones/codes for receiving, transmitting, or both.
- Repeaters configured with identical tones/codes for transmit and receive can be used by most radios.
- Repeaters configured with different tones/codes for transmit and receive can only be used by split-tone capable radios.
- Only radios capable of configuring individual transmit and receive tones/codes can access split-tone repeaters.
- Repeaters not using any tones/codes are considered 'Open', and can be used by all GMRS radios.
-
To access repeaters using tones/codes, the radio must be configured as
follows:
- Transmit (Tx)
- Configure the radio channel with the Tx tone/code
identical to the Rx tone/code specified for the selected repeater.
- Only correctly coded transmissions received by the
intended repeater will be broadcast on the channels Rx frequency.
- Transmissions not received by the repeater will not be broadcast
or heard by other radios monitoring the repeater.
- Receive (Rx)
- Configure the desired radio channel with the Rx
tone/code identical to the Tx tone/code specified for the
selected repeater.
- The radio will now ignore all audio transmissions not
encoded with the configured tone/code.
- Use this configuration to limit your radio Rx activity to other radios
using the same repeater.
- Skip Rx tone/code configuration to monitor all channel activity,
both local (simplex) and repeater (duplex).
