Repeaters versus simplex radios

I’m new to GMRS (and licensed) but can’t figure out repeaters. One frequency (usually the input Freq.) is not on a standard channel. How is this supposed to work, or do I need to buy more sophisticated radios than bubble pack type walkie talkies?

Harvey Berger
Azusa, CA


A repeater works with two freqs - an input and an output freq.

Input freq: This is the signal/audio that gets repeated on the output freq. The mobile transmits on this freq and receives on the repeater output freq.

Output freq: This is the repeated audio from the input freq. Its repeated at a much higher output power and the antenna is usually up high on a tower or tall building so the signal can reach out much further than the mobile or portable on the input freq. The repeater transmits on this freq and receives on the input freq at the same time(Full Duplex).

VHF Hi Band = No standard inputs
450-470Mhz Standard Input = +5Mhz (IE: 453.500 Output, 458.500 Input)
470-512Mhz Standard Input = +3Mhz (IE: 472.400 Output, 475.400 Input)
800Mhz band = Standard inputs are -45Mhz
900Mhz band = Standard inputs are -39Mhz

Very few (currently know of 1 of the motorolas) ‘bubblepack’ FRS/GMRS radios allow repeater use.

But before you worry about buying a radio, you need to discover what repeaters, if any, are in your area, and what they require to use.

You need permission to use any repeater, and while many use simple CTCSS or DCS for access, some use tones not available on bubblepack radios at all (not one of the common 32 tones), and many more use ‘split tones’, different CTCSS/DCS (or both) tones on input and output, and none of the bubblepacks will do that.

Seconding the comment about talk to the repeater operators…

Basically, the repeater has an input and an output channel. Anything it get on the input, it spits back out again on the output.

To work with a repeater, your radio must understand that it’s working with a repeater and switch its frequency to the TX (input) channel as soon as you push PTT, then switch back to RX (output) channel when you let go. That’s what ‘repeater capable’ radios do if you turn on repeater mode.

However as mentioned some repeaters do odd things with PL tones (CTCSS) so you may need a higher end radio depending on your area…