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Thursday, March 08, 2018

DMR for local communication

A really nice benefit with DMR is that when used for local communication among amateur radio operators, each person can easily be identified. 

This can be especially useful when used to support special events or emergency volunteer work with organizations such as ARES, RACES, MRC and the Red Cross to name just a few.

It is suggested that every amateur radio operator is registered for a 7 digit DMR ID in order to help identify users. This can be accomplished on the DMR-MARC website.

Radios such as the TYT MD-380,  MD-2017 and  Retevis  HD1 support enhanced caller ID like functionality with others like the Radioddity GD-77 offering more basic visual identification. The entire contact database or a large part of it can be loaded into radios.

Offline Use

Storing the entire database of DMR users has so many benefits, but what about knowing what frequency to use for non-repeater or hot spot use?

DMR works great for radio to radio communications and still provides easy user identification for things such as call-sign, name and license location. Having the database and a dedicated list of "radio to radio" channels is a really good idea.

Perhaps one day, DMR radios that offer GPS will be able to dynamically share related GPS coordinates and translate them to a ZIP code or other postal code database to give high level detail on a user location

Here is a suggested channel plan for national and local "radio to radio" operation also known as simplex communications.

Analog and digital operation is supported as noted with channels on 446.000 and 446.500 MHz which are already widely known in North America.  The proposed 427 MHz channel plan makes use of underutilized spectrum available under the United States 70cm band plan, but does have some limitations near the border of Canada.

A PDF of the above channel chart for UHF can be found here along with some code plugs for popular radios.

What about VHF?

The 144-148 MHz band in North America is pretty congested with repeaters and frequencies supporting satellite and digital modes like APRS, so it seems the equivalence to the analog 146.52 MHz calling channel would be 145.79 MHz and 145.510 MHz as a secondary channel

Helpful Tips 

  • Be sure to set your radio to talk group 99 or to also have a receive group for both 99 and 9
  • Use time slot 1 and color code 1
  • Set your radio to "admit always"
  • Experiment with DMO mode if your radio supports that feature.
  • Create scan lists to uncover new users in your area easily
  • Try to use your hot spot on one of the five 427 MHz frequencies

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