Technically Speaking, How Does Midland’s Group Mode Work?

[mbrun]

I own a collection of Midland GXT1000 Radios FCC ID #MMAGXT50. These radios have a proprietary ‘Group Mode’ feature that allows two way communications between radios with the same Group Mode setting. In general, radios in Group Mode behave similar to radios that merely use CTCSS or DCS codes.

 

I have assumed for some time that this Group Mode is really nothing more than a different way of assigning the various CTS an DCS already built into the radio. However, when I attempted to confirm this I had no success. I tested this by enabling group mode on a transmitting unit and then trying all the different CTCSS and DCS codes on a receiving radio. The receiving radio never broke squelch when any CTSSS or DCS was active.

 

So what I am trying to figure out is, technically speaking, what specifically is Midland doing to achieve Group Mode behavior? Anyone out there know?

 

 

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[Lscott]

Does the radio programming software help file give any clues? Other radio manufacturers offer a similar feature. It typically works using a proprietary signaling method.

 

For example one manufacturer let’s users program in a multi digit DTMF code, like a touch tone telephone number, and only radios with a matching code will open the squelch so you can hear the audio. All other radios the audio will remain muted.

 

Some others use two-tone or five-tone signaling. I think Motorola uses their own proprietary system MDC.

 

https://en.wikipedia.org/wiki/Selective_calling

 

 

 

[mbrun]

The GXT1000 does feature programming software. It is only front panel controllable. Currently this is still Midland’s top-of-the-line GMRS radio.

 

I have searched the web to no avail. I suppose if it were targeted for the advanced user there might be technical information widely available.

 

 

 

 

Does the radio programming software help file give any clues? Other radio manufacturers offer a similar feature. It typically works using a proprietary signaling method. For example one manufacturer let’s users program in a multi digit DTMF code, like a touch tone telephone number, and only radios with a matching code will open the squelch so you can hear the audio. All other radios the audio will remain muted.Some others use two-tone or five-tone signaling. I think Motorola uses their own proprietary system MDC. https://en.wikipedia.org/wiki/Selective_calling

 

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[mbrun]

So I am wondering if Midland is actually using non-standard CTCSS and DCS Codes for Group Mode functionality.

 

I don’t currently have a way to scan for the codes that are actually being broadcast, but I would I suppose that is a possibility.

 

What other times of continuous data transmission does the FCC allow to be broadcast via GMRS? I know Text Messages, Location Data and PL codes are all permitted. Anything else?

 

 

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[berkinet]

FWIW, I seem to recall reading somewhere that the Group Mode feature was for signaling other radios, but not for talking.

[mbrun]

Yes, there is signaling feature you can take advantage of while in group mode (a useless implementation IMO).

 

Coincidentally, the number of group codes available on the radio is One more than the total number of DCS and CTCSS codes available on the radio. Valid codes range from 00-142.

 

 

FWIW, I seem to recall reading somewhere that the Group Mode feature was for signaling other radios, but not for talking.

 

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