MMDVM Duplex hotpot in Simplex mode

posted in: DMR | 9

For anyone having issues with their Duplex MMDVM hotspot, this is a just a quick post about using a Duplex MMDVM hotspot in Simplex mode.


When I first received my hotspot, I had a lot of problems getting it to work correctly. Some of these have now been resolved, thanks to the work of Andy CA6JAU, making changes to his firmware.

Nevertheless, it can be handy for testing, to initially run the hotspot in Simplex mode..


Unfortunately just selecting Simplex from the Controller Type  does not work.

Changing to Simplex Node removes the separate Transmitter and Receiver frequency boxes in the General Configuration, and replaces it with a single “Radio Frequency”.


The trick to use your Duplex hotspot as a Simplex hotspot is to select the MMDVM_HS_Hat rather than MMDVM_HS_Dual_Hat



In this mode the SMA socket labelled Rx on some boards and AE1 on others, is now the one that will be used.

In my case I connected this to my external antenna, but you could just use one of the cheap 10cm long antennas which are supplied with these sorts of boards.


And the board works just fine !




9 Responses

  1. ken

    excellent, thank you

  2. rswenton

    Thanks for this! We really appreciate your efforts and insight. Now I can provision my duplex hat for something useful. -Rick, W1RHS

  3. Keith Leggett

    Thanks Roger .. just couldn’t get the dual hat working, now all operational on Fusion using your simplex option guide, however tx on DMR is registering but no rx on the Ailunce HD1. Next job for tomorrow.
    Also had to reset the RX and TX offset to -500 – no offset reference on the board when received. Still, a good way of learning!

    Keith GM4JKZ

  4. Pablo

    Try to enable the talk around and RX group add the channel and contact talk group name and number in a channel select the rx contact and tx contact the same contact with programing radio software if you have questions send me mail to i have DM-1702 very similar like you radio. Remember use oposite frecuency programed in hospot and radio.

  5. Roger Clark

    TalkAround is not currently supported in any of the released versions (either Tier1 or Tier2).

    I am adding a “Quick menu” to the Tier2 version, which is accessed via the Orange button, on both the Channel and VFO screens and one options with this is to swap the Tx and Rx frequencies.

    However the Tier2 version is not very stable at the moment, so I will not be releasing another update until I have made it more stable.

    But the Tier2

  6. steinmaier

    The range in very low , (in the duplex mode ) the range RX is <50 meters. No problems to TX.
    Did you have this problem?
    Best 73" F4INJ , FABIEN.

  7. Roger Clark


    The receivers on these units are extremely insensitive.

    But I think the simplex versions are the same

    The problem appears to be the design of the RF section, because the module used by the Zumspot Libre board, uses the same chip (ADF7021) and is much more sensitive.
    But the RF module uses a RF switch chip to change the antenna connection between the Rx and Tx inputs of the ADF7021, whereas all the hotspot boards have the Tx and Rx pins on the ADF7021 connected together via some inductors and capacitors.

  8. Steinmaier

    Ok, This module is very very insensitive.
    I want create a relay wide range (PISTAR (DMR+POCSAG)).
    Do you think I should buy to work best?.
    Best 73. F4INJ , Fabien

  9. Roger Clark

    The only way to have DMR + POCSAG long range is to convert 2 compatible FM transceivers and use a MMDVM board e.g.

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