Analog APRS messages to DMR

Some time ago I was researching an option to send SMS messages to my DMR TYT MD-380 portable. It seems there is a link between the APRS network and DMR repeaters connected to the Brandmeister network. This enables you to send an APRS message via 1200 Bd packet at 144.800 to a DMR radio and vice versa from a DMR radio to an APRS station. But first some things need to be aligned at the DMR side.

I assume you’ll have a DMR transceiver and a CCS7 number. With this you’re already QRV via DMR.

Next step is to tell the Brandmeister network which transceiver you’re using. This is important because different brands of DMR transceivers have different ways to handle SMS messages. You’ll also have to setup the call and SSID to determine the identity under which you’ll forward the messages from the APRS to the DMR network. You can setup this yourself using the DMR Selfcare (create an account first if you don’t already have one):  https://www.dstar.su/selfcare/#hdmr

Within Selfcare I’ve set my transceiver to a Chinese type and my APRS call to PE1ITR-13. See the picture below.

selfservice

For the Brandmeister network it’s also important to know at which repeater you’re currently QRV. So just key up shortly while your in range; more advanced DMR transceivers handle this automatically, but my cheap Chinese handheld doesn’t. To avoid interference with others I mostly do this using talkgroup 9 slot 2.

APRS to DMR

Messages from APRS to DMR have the standard APRS format. In my Selfcare setup I’ve determined to be available as PE1ITR-13. A message via APRS then has the format:

:PE1ITR-13:Hello 123

Below the message format as described in the APRS documentation is shown.

aprs_message_format

DMR to APRS

Suppose I want to send a message to PD2CWM-7. Create a message using the DMR transceiver with the format:

PD2CWM-7 Hello 123

Then send this message to 5057.

An example

In this example a message will be sent with a Yaesu FT2D handheld while it will be received by a TYT MD-380 handheld. The message will be sent by PD2CWM-8 at 144.800 MHz in 1200 baud packet into the APRS network.

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The message containing the text ‘test aprs porto to dmr porto’ at the FT2D will be sent to PE1ITR-13.

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Immediately the message will be received by the TYT MD-380.

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Applications

I also wanted to receive the propagation warnings I’ve mentioned earlier in the blog via my DMR handheld. Because there’s a link between the APRS and DMR network I can send these messages as an APRS message to the APRS network and then forward them to my DMR handheld. I now have an extra option for this created in the propagation alert system, so now it’s possible to receive these warnings also at the DMR portable. The system only needs to know which call and SSID the messages forwards to the DMR network. If you would like to receive sporadic-e warnings just drop me a message so I can add your call and SSID to the alert system.

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Experiences

The system as described works really well and there is almost no delay between the moments a message is sent and when it’s received. Messages are not stored, so when you’re out of range you’ll probably miss a message.

The connection to the DMR repeater has to be really well. At the limits of the range of a repeater, when voice is only decoded by positioning the radio at best possible reception, it’s for sure not good enough to receive SMS messages.

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