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Texting On GMRS Vs. MURS


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I am trying to learn a bit more about simplex texting on GMRS vs. MURS. Is texting (data) permissible on MURS, but a bit more restrictive on GMRS? I know the Garmin RINOs limit texting to 13 characters (one second). Is that a self-imposes limit? I recall reading that short data transmission are allowed, but how short is that? Is the "one second rule" coming from the FCC?


I haven't looked into the Motorola T800/801s for a while. How many characters can be sent at a time with those?   

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Good Day Jim. Welcome to myGRMS.

Data Transmissions in GMRS (the methodology used for sending texts and location information) is regulated by the FCC.

The one second duration limit, and the frequency at which messages can be sent is defined in article “§ 95.1787 GMRS additional requirements. “. Here is link to the rules where you can read the compete details:


The number of characters that can be sent is not expressly regulated in any way that I have read to date, but I would imagine that the 1 second limit in combination with the technology used by the manufacturers to send them imposes the limit.


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As noted above, the maximum data is regulated by timeframe (1 second). With that 1 second maximum, FM packet has a realistic maximum data rate of 9600 baud, but more commonly used is 1200 baud, similar to APRS. Since the messages aren't just sending message characters, but require a header to include destination, and maybe some error correction, you are limited to 10 characters. This is all based on the bandwidth of FM radio, time, and the ability to decode/encode the data to AFSK sounds (think your 56k modem sound from 1996).

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