Extended Range Direct Mode

Extended Range Direct Mode enables repeater operation on a simplex radio channel. Radios on an ERDM channel transmit on one slot and receive on another slot - the frequency is the same.

With this you get:
  • Repeater-like coverage
  • No need for a 2nd frequency - your simplex channel can be reused.

In this configuration, dual slot operation is not possible and you need to be using a SLR series repeater. IP based dispatch solutions, like SmartPTT Plus and TRBONET Plus, are supported. It also only supports single site conventional operation so no trunking or IPSC.

This feature requires R2.7.0 firmware and is supported on all current generation MOTOTRBO radios. My understanding is that this feature will also work on other makes of DMR radios.

If you want IPSC like operation on simplex try the Vertex Standard EVX-Link product.

Postscript 20.01.17

Before deploying ERDM, you must check with your local authorities as a simplex frequency licence is tied to a smaller geographical area (i.e. no more than 5km from point X is allowed). Installing a repeater (even though it uses a single frequency) may violate your licensing conditions.

- Thanks and credit to Craig Matthews for pointing this out.

Postscript 04.03.17

A Circulator cannot be used as it does not offer sufficient isolation (<30dB).

- Thanks to Jim for trying this out. Even a negative result is a result. 


  1. Very good news, Great Wayne


  3. Do we need two antennas for the repeater to work in single frequency direct mode ?

    1. This seems to be the easiest way to arrange the antenna system.

      There is mention in the system planner of switching a single antenna between receive and transmit by using an output on the accessory connector but I don't have any details.

      I thought of using a circulator but have never tested that.

    2. The MOTOTRBO CPS help show:
      Antenna Relay Delay Timer (ms)
      This feature is applicable to MOTOTRBO Conventional and MTR3000 base radio/repeater and SLR series repeaters in Analog mode only.
      so, maybe can't use at this case?

    3. Antenna Relay is for when the repeater is being used as a base station and has nothing to do with ERDM.

    4. I test the SLR8000 in Extended range direct mode using an circulator as you suggested. I manage isolation of 28,5 Db between TX and RX port, it is working with 6 watts Rf power with no indication of desensitization, of coarse I used a antenna with very low VSWR. But I am afraid to use more power, after all SLR8000 is an expensive repeater! What is your opinion?

    5. I would not use a circulator then. Thanks for doing this test. I'll edit this post to reflect your feedback. :-)

  4. I upgraded a SLR5500 and some DP4801 radios to firmware version R02.07.00.04 and I realised that "Extended Range Direct Mode" feature was needed to purchase for SLR5500 repeater. It's not a free feature. I could not see the price of this feature in the current repeaters price list which is published in the MOL.

    1. List Price : $400.00

      Part Number: HKVN4490A
      • License key required to activate the
      "Extended Range Direct Mode" feature in
      an SLR 5500 / SLR 8000 repeater.
      • Also known as "Single Frequency
      • Significantly increases coverage area on a
      single frequency beyond a direct mode
      • Does not require additional frequency
      usually required on a repeater.
      • Inbound burst is repeated 90 ms later on
      outbound (time division duplex).

  5. show the correct settings EXTD RANGE DIRECT MODE in portable radio DP4801, SL4010


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