DMR SMS Simplex Messaging

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One of many benefits of Digital Mobile Radio (DMR) Digital is the ability to send SMS/text messages. While it is possible to send text messages through the Brandmeister DMR repeater network, and even send text messages through the SMS Gateway to the cellular network (yes, you can send a text message to a cell-phone with your radio), our interest today is in simplex text messaging between two (or more) DMR radios.

With a digital simplex channel programmed into your radio, go to 'Menu' and select 'SMS Messages'. Choose 'New Message' and type in your message from the keypad (most radios also allow you to store a number of pre-programmed messages). As with text messages on the cellular network, DMR text messages are limited in length to about 100 characters. Click 'Send' and then either select a contact from your list, or click 'Manual Dial' and enter the DMR ID number of the station/person you want to send the SMS/Text Message to. If you are within range of the other radio and you are both on the same frequency you will be able to text back-and-forth, just as you can on a cell-phone.

One of the advantages of DMR SMS Messaging is that messages can be received without the need to monitor the radio, listening for a call. A DMR SMS message received by your radio is stored in the radio's message inbox until you are ready to read it. DMR SMS Simplex Messaging also offers some increase in privacy as someone monitoring voice traffic on the channel won't hear the content of the SMS message. DMR SMS messages are only received (stored) by radios programmed with the ID to which the message is being sent (although it is possible to set up a radio to receive and store all SMS messages on the frequency). Yes, you can use the same channel/frequency to send both DMR Voice and DMR SMS messages. While neither SMS messages nor voice communication is truly private on your DMR radio without the encryption function turned on (encryption is not allowed on Amateur Radio frequencies), it is still much more private than analog voice.

There are some downsides to DMR SMS simplex messaging. The first is range. While you can communicate over several kilometers, you are still limited to communicating with those in your local area. Second, for a message to be received the radio you are sending to must be on at the time the message is sent. There is no store and forward function like there is with a cell-phone text message. You may also find that there are dead zones where you cannot get a signal out to your intended recipient - although the same problem exists with cell-phones where you may find yourself in a no service area.

DMR SMS simplex messaging is a useful tool for the survivalist, providing a text message system that is independent of the cellular companies, and will continue to function during a power outage or after a complete failure of the cellular network in your area.       

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