Amateur Radio Guide to Digital Mobile Radio

A comprehensive introduction to DMR is available to hams at no cost, thanks to the efforts of John Burningham <W2XAB>. His “Amateur Radio Guide to Digital Mobile Radio” won the 2016 Technical Achievement Award at Dayton Hamvention and the second edition was published in 2019. Even if you think you know how DMR works, this guide is full of useful information.

If your view of DMR is limited to the perspective of Pi-Star and Brandmeister or TGIF, this free book tells the rest of the story in its 27 pages. It is an easy read and will enhance your DMR knowledge.

Duplex Hotspot Reliability Revisited

Last August, I presented a solution for the “lost transmission” syndrome when using an MMDVM duplex hotspot. Several members of the 020 Digital Multiprotocol Group and I remain dissatisfied with our overall user experience. Granted, fewer transmissions are being lost than at first, but overall the number of transmissions during a longer QSO that fail to properly negotiate with the hotspot are higher than we’d like.

Earlier this week, 020 member Scott <KB2EAR> did some further digging and came up with aditional ideas found on the interwebs. I’ve taken these recommendations, added some others, and tested extensively. Here is my new set of recommendations for MMDVM duplex hotspot reliability when using DMR. This supersedes my article from August 29, 2019.

1) Update to the latest firmware.
2) Run the MMDVMcal procedure to minimize the BER
3) Set the MMDVMHost modem TXDelay=50
4) Set the MMDVMHost modem DMRTXLevel=55
5) Set the MMDVMHost DMR TXHang = 20
6) Turn off any mode other than DMR to avoid protocol scanning negotiation
   issues.

I withdraw my earlier recommendation to reduce the DMR preamble. After much consideration, it seems to be unnecessary, with no clear benefit.

So far, using these setting on 2 different N5BOC duplex hotspots have yielded excellent results and reliability. Negotiation failures are now the rare exception. Tests were conducted with an Alinco DJ-MD5, a TYT MD-380, a CS-700 and a Hytera PD-365. Give these settings a try and let me know how they work for you.

73 de K2IE

020 in 2020: An Update on the 020 Project Multiprotocol Digital Network

You may know it as CNJHAM, because that is how it all started. CNJHAM was first implemented as a lone StarNet smart group. CNJHAM then begat XLX020. Hardware transcoding was soon implemented and followed by links to Brandmeister DMR and YSF Fusion. In this new year, we’ve added Wires-X (for connection from Fusion repeaters) as well as P25 connections.

CNJHAM/XLX020A can be reached via the following methods:

D-Star Callsign RouteCNJHAM via Quadnet
D-Star ReflectorsXLX020A, XRF020A, REF020DXLX020A preferred
D-Star RepeatersNJ2DG-A
NJ2DG-C
W2RJR-B
Fulltime
Brandmeister DMRTG 31340CNJHAM
Fusion YSFYSF 44977US CNJHAM
DTMF 44977
Wires-XCNJHAMDTMF 28255
P25TG 31340Pi-Star
NXDNTG 31340Pi-Star
XLX DMRXLX020AEnable DMRGateway in Pi-Star
XLX YSFXLX020ASome Pi-Star config required

Jersey StrongWhatever the protocol, CNJHAM is Jersey Strong!

73 de K2IE

D-Star & DMR Interoperability

If you’re a fan of either D-Star or DMR, you have probably noticed the proliferation of multi-protocol gateways. These gateways, such as the XLX020 system, permit users of radios of one type to communication with users of radios of another type. Multiprotocol gateways help to defragement the amateur digital landscape.

However, there can be issues if the transmitting operator is not registered on both systems. Have you been on a DMR radio and seen the transmitting party display as radio id 0? They are a D-Star (or Fusion or P25 or NXDN) operator who has not registered a DMR radio number.

For DMR operators who have not registered with their nearest D-Star gateway, transmissions could even fail to pass through the D-Star gateway to connected D-Star repeaters.

Therefore, k2ie.net highly recommends that all amateurs using any digtial voice mode register for BOTH a DMR radio id and with a local D-Star gateway, whether or not you have a corresponding digital radio.

You can register for a DMR radio ID at http://www.radioid.net. Hams in Europe and Africa should register at http://www.ham-digital.org.

If you’re not sure of your local D-Star gateway, you can follow the instructions at https://www.dstargateway.org/D-Star_Registration.html.

73 de K2IE

Duplex Hotspot Reliability Solution

So you’ve bought a new duplex MMDVM hotspot such as the one from N5BOC. You want to experiment with different DMR networks on each of the timeslots. You’ve set the recommended offset values in the MMDVM Expert settings. Yet every third or fourth PTT press results in a lost transmission. You’re so frustrated you want to throw your radio and hotspot across the room. Sound familiar?

I’ve spent a couple of months chasing down this issue, reading post after article on this subject. The consensus so far has been:

1) Update to the latest firmware.
2) Run the MMDVMcal procedure to minimize the BER.
3) Set the DMR preamble time on your radio to 960 ms.

After weeks of poor results, I came upon the solution that has worked for me (and for others) in a manual for the Anytone 878 produced by Bridgecom. Bridgecom recommends a DMR preamble duration of 100 ms.

1) Update to the latest firmware.
2) Run the MMDVMcal procedure (or enter the sticker offset
values for RXOffset and TXOffset).
3) Set the DMR preamble to 100 ms.

Well, I was testing on an Alinco MD-DJ5, a radio very similar to the Anytone 878. So I tried the preamble setting (called Wake Head Period in my software).

I have now achieved the mystical “five 9s” of reliability. I press PTT, I talk, my transmission gets received.

Ah, the sweet smell of success… And kudos to Bridgecom for the level of support that provide for Anytone 878 users.

This solution has worked so far with an Alinco DJ-MD5, a Motorola XPR, and a CS-700 (where I had to use 120 ms because the dropdown increments in steps of 60.). Oddly, my Hytera PD-365 does not support values lower than 360.

73

Pi-Star Configuration for XLX020

Some simple changes must be made to the configuration of a Pi-Star based hotspot before it can access an XLX Reflector. Thanks to our partner in the “020 Project”, Scott <KB2EAR>, who helped with following guidance.

To connect to XLX020 via DMR you must configure your Pi-Star hotspot to use DMRGateway. Before you begin, make sure you hit the update button on the Pi-Star menu.

If you have not yet enabled DMRGateway, you will find the DMR Configuration looking something like this:


To enable DMRGateway change DMR Master to DMRGateway (very top entry).

Click apply changes and wait for the menu to come back up. Next change XLX Master to XLX_020. XLX Startup Module will usually be either A (Central New Jersey) or C (Beyond New Jersey, including REF020A & Peanut users). Turn on the XLX Master Enable slider.

Click apply changed. Once the configuration above has been applied you should be ready to go. Next, program the radio.

To talk via DMR on an XLX reflector, you’ll need to use a channel programmed with TG 6. Also set up a receive group list with TG6 so you will receive signals from the hotspot.

If you want to move your hotspot between reflectors and modules, commands are sent via a private call. These should be entered into your digital contact list.

6 Group Call - Talk on the XLX Reflector
64000 Private Call - Disconnect Channel
64001 Private Call - Switch to Channel A
64002 Private Call - Switch to Channel B
64003 Private Call - Switch to Channel C
64004 Private Call - Switch to Channel D
64005 Private Call - Switch to Channel E
64006 Private Call - Switch to Channel F
65000 Private Call - Query Status
68020 Private Call - Connect to XLX Reflector 020

XLX020A is the gateway to the CNJHAM/XRF020A/REF020D network.

XLX020C is the gateway to the Peanut/XRF020C/REF020A network.

See you in 020 land.

73

The “020” Reflectors

D-Star users have long known about REF020. Reflector 20, as many call it, is one of the original D-Plus Reflectors. A number of repeaters in the New Jersey/New York/Pennsylvania region link to it, including powerhouse K3PDR in Philadelphia and NJ2DG in Martinsville, NJ. It was recently relocated to the cloud by its operator (Scott KB2EAR) when when the site where the server was housed became unavailable. Historically, the busy channel tends to be REF020A.

During the weeks that Reflector 20 was down, I started exploring D-Star smart groups as a way to get together on the air with some of the folks that I talk to regularly. Smart Group CNJHAM was created on the QuadNet array.

Smart Groups can be a bit confusing on repeaters if you don’t know what group is being used as you come into range. My friend Ray <W2RJR> is playing with a low profile Pi-Star based repeater so we decided that repeater use would be simpler if it could connect to a reflector. Then the only destination route needed is CQCQCQ. So XRF020 was born.

Initially, there were challenges getting XRF020 getting listed in the right directories. You see, there is supposed to be one XRF directory that is authoritative, but not all gateway systems seem to pull data from the same place. Pi-Star uses one list, OpenSpot another, and DV4mini yet another. OpenSpot listed XRF020 right away. DV4mini uses the XLX list and you could have an XRF and XLX using the same number, which is “interesting”. Pi-Star took weeks to list XRF020 until I went to the “top guy”. Then it was handled immediately. Once I learned that XLX reflectors self-register, XLX020 was born.

CNJHAM - Our Central New Jersey smart group conference
REF020 - The original D-Plus Reflector 20 operated by KB2EAR
XRF020 - An XRF Reflector that speaks D-Plus and DCS as well as DExtra
XLX020 - A multiprotocol reflector that bridges digital modes

Here is the lay of our digital land.

Smart Group CNJHAM is where a few of us in the Central NJ area meet up daily. It is more or less our local digital intercom, but you are welcome to stop by and say hello. You can also say hello via XRF020A and XLX020A, as well as REF020D. They are all linked. The NJ2DG-C repeater is linked to REF020D, so you can get in that way too.

         CNJHAM <==> XRF020A <==> XLX020A <==> DMR/YSF
|
REF020D

If you’re an REF020 user, then you’ll want to know that REF020A is linked fulltime to XLX020C. You can connect to the XLX side of things via DMR, D-Star, or YSF. You can also get in via PA7LIM’s Peanut.

             REF020A <==> XLX020C <==> DMR/YSF/Peanut

See you in 020 land.

73

April 1 DMR Security Update

A new security implementation for DMR repeaters has been announced.

It is called “Color of the Day”. The color code will be randomized and rotated daily to ensure that only those with the correct seed will be able to access repeaters. To get the seed you need to make a Paypal donation to the Amateur Radio Security Cabal Inc. This is a not-for-profit organization of amateurs interested in security and is located in Lichtenstein.

For further information please Google “Aprilscherz”.

November DV4mini Image Update

The K2DLS DV4mini image for the Raspberry Pi 2 and 3 (only!) has been updated to include the October 12 release of the DV4mini Control Panel.  This includes XRF through letter Z and REF up to 100 for the D-Star users.  The image will fit nicely on an 8 GB SD Card.

DV4mini RPi Image Updated to Raspbian Stretch

The K2DLS DV4mini image for the Raspberry Pi 2 and 3 has been updated to Raspbian Stretch.  The DV4mini client and BMXTG 1.3 start automatically upon boot.  VNC has been updated to RealVNC.  Both VNC and ssh are started by default.

The installation fits nicely on an 8 GB SD card and it looks great on my 7″ touchscreen display.

The default password for the pi user is “raspberry” — please change it immediately!

The image may be found here.