DMR Hotspot from SharkRF

Amateur adoption of Digital Mobile Radio (DMR) continues to increase, with a number of new innovations playing out. It was way back in 2012 when I wrote this article about DMR for CQ VHF Magazine: TRBO Hits the Amateur Bands. 

A few years ago, I picked up some used MOTOTRBO gear to use on our local DMR repeater system (MOTOTRBO is Motorola’s version of DMR). Here in Colorado, the Rocky Mountain Ham Radio group has been instrumental in establishing a great network of DMR repeaters, a real asset for Colorado radio amateurs. See Rocky Mountain Ham Radio TRBO/DMR Network.  Worldwide, the DMR-MARC organization has created a robust network of MOTOTRBO repeaters in over 60 countries.

A more recent development is the establishment of the BrandMeister Network, which promotes more of a homebrew approach to DMR. This evening, the BrandMeister dashboard shows 634 industrial repeaters (commercial equipment), 263 homebrew repeaters and over 1300 hotspots of various types.  A variety of DMR hotspots are available, including the DV4mini. I’m not going try to list all of the hotspots available as I’m sure I’ll miss something.  The SharkRF openSPOT caught my attention because of this excellent review by John ‘Miklor’ K3NXU. Because of its popularity, the openSPOT is on backorder (price: 182.5 Euro).

This HamRadioConcepts video walks through the setup and basic operation.

I thought the openSPOT would be a good widget to have around the shack. It is a standalone hotspot, so I don’t have to dedicate a computer to it. Also, it is very turnkey…no assembly required…but some configuration to work out. Its user interface is a web page that you access via your local network…nicely done. I got it working in less than one hour and have been fiddling around with it ever since.

Hotspots are a funny item. They have very limited RF range, so their main purpose is to provide local RF access into the network (just like your Wi-Fi hotspot). One role they play is to provide fill-in coverage when no repeater is available. Another role they fill is being a personal device that can be connected to your favorite reflector or talk group.

I should point out that the openSPOT also operates as a D-STAR and Yaesu Fusion (YSF) hotspot. You just change the configuration of the modem and it starts speaking the selected modulation. More surprising is that I was able to use a YSF handheld radio to talk to the openSPOT which routed me to a DMR talkgroup. Yes, a Yaesu YSF radio talking on DMR.

The first thing I noticed when listening to some of the more active talk groups is that it seems like every person getting on the system said “I just got this Tytera MD-380 radio and you are my first DMR contact.” OK, sometimes it was a Connect Systems or Motorola radio but the MD-380 at around $100 is having a big impact. I picked up an MD-380 and while its not quite as nice as my Motorola, I really do like the radio. (Note that there are other low cost DMR radios that have serious technical issues.) There will be other radios on the market…the technology will keep improving and improved models will hit the market. Right now, everyone is wondering who will create a good dualband 2m / 70cm transceiver for DMR.

I see some very strong technology and market trends in play here that are going to impact the ham radio world. First off, DMR is a true industry standard (ETSI),  well designed and documented. Second, we are seeing multiple radio vendors offering competitive, low cost transceivers. Third, there is high quality commercial repeater gear available from land mobile providers such as Motorola and Hytera. But there’s one more thing that really tops this off: the number of ham-built products emerging that are focused on DMR. This is classic ham radio adaptation and innovation that leverages commercial gear for ham radio use.

Stay tuned…this is going to be interesting!

73, Bob K0NR

The Cacophony of Digital Voice Continues (Part 2)

Digital transmissionThis post is a continuation of The Cacophony of Digital Voice Continues (Part 1), so you probably should read that one first.

All of the popular amateur digital voice (DV) systems (D-STAR, DMR and YSF) use the AMBE vocoder (voice codec) technology. This technology was developed by Digital Voice Systems, Inc. and is proprietary technology covered by various patents. The use of proprietary technology on the ham bands causes some folks to get worked up about it, especially proponents of an open source world. See my blog posting: Digital Voice at Pacificon and this presentation by Bruce Parens K6BP: AMBE Exposed. Codec2 is an alternative open voice codec developed by David Rowe, VK5DGR. David is doing some excellent work in this space, which has already produced an open codec that is being used on the ham bands. FreeDV is an umbrella term for this open codec work. Here’s a recent video of a presentation on FreeDV by VK5DGR.

It will be interesting to see if and how Codec2 gets adopted in a DV world already dominated by AMBE. After all, a new codec is another contributor to the digital cacophony. On the HF bands, it is easier to adopt a new mode if it can be implemented via a soundcard interface (which FreeDV can do). Any two hams can load up the right software and start having a QSO. The same is true for weak-signal VHF/UHF via simplex. (Note that Flexradio also supports FreeDV, showing how Software Defined Radio (SDR) has an advantage with adopting new technology.)  VHF/UHF repeaters are trickier because you must have a solution for both the infrastructure (repeaters and networks) as well as the user radios.

The vast majority of digital repeaters support just one digital format. For example, a D-STAR repeater does not usually repeat DMR or YSF transmissions. Interestingly, DMR and YSF repeaters often support analog FM via mixed mode operation for backward compatibility. It is definitely possible to support multiple digital formats in one repeater, but the question is will large numbers of repeater owners/operators choose to do that? With existing DV systems, the networking of repeaters is unique to each format which represents another barrier to interchangeability. In particular, most of the DMR infrastructure in the US is MOTOTRBO, which won’t ever support D-STAR or YSF.

In the case of a new vocoder, we can think of that as just a new format of bits being transported by the existing DV protocol. DMR, for example, does not actually specify a particular vocoder, it’s just that the manufacturers developing DMR equipment have chosen to use AMBE technology. So from a technical viewpoint, it is easy to imagine dropping in a new vocoder into the user radio and having it work with other identical radios. Of course, these radios would be incompatible with the existing installed base. Or would they? Perhaps we’d have a backwards compatibility mode that supports communication with the older radios. This is another example of putting more flexibility into the user radio to compensate for DV incompatibilities.

One objection to AMBE is the cost of the technology, especially when compared to free. When D-STAR radios first started using AMBE codec chips, the chip cost was rumored to be $25 to $50, but I don’t have a solid source on that. Now, I see that Tytera is selling a DMR handheld at around $100, including AMBE technology inside, so the codec can’t be very expensive. If a free codec starts to be a credible threat, it will put additional pricing pressure on the AMBE solution.

A potential advantage of Codec2 is superior performance at very low signal-to-noise ratio. We’ve all experienced the not-too-graceful breakup of existing DV transmissions when signals get weak. Some of the Codec2 implementations have shown significant improvement over AMBE at low signal levels.

Conclusions

Repeating a key conclusion from Part 1:

  • For the foreseeable future, we will have D-STAR, DMR and YSF technologies being used in amateur radio. I don’t see one of them dominating or any of them disappearing any time soon.

Adding in these conclusions for Part 2:

  • Codec2 will struggle to displace the proprietary AMBE vocoder, which is well-established and works. The open source folks will promote codec2 but it will take more than that to get it into widespread use. Perhaps superior performance at low signal levels will make the difference.
  • Repeater owner/operators will continue to deploy single-DV-format repeaters. This will make multiformat radios such as the DV4mobile be very attractive. In other words, we will deal with the digital cacophony by having more flexible user radios. This will come at a higher price initially but should drop over time.

Repeating this one from Part 1:

  • A wild card here is DMR. It benefits from being a commercial land mobile standard, so high quality infrastructure equipment is available (both new and used gear). And DMR is being embraced by both land mobile providers (i.e., Motorola, Hytera) and suppliers of low cost radios (i.e., Tytera, Connect Systems). This combination may prove to be very powerful.

Well, those are my thoughts on the topic. I wish the DV world was less fragmented but I don’t see that changing any time soon. What do you think is going to happen?

73, Bob KØNR

The Cacophony of Digital Voice Continues (Part 1)

Digital transmission

It wasn’t that long ago that I commented on the state of digital voice on the VHF/UHF ham bands: Digital Voice Balkanization. We have three main competing (incompatible) standards in the running: D-STAR, DMR and Yaesu System Fusion (YSF). At a high level, these three formats all do the same thing but there are significant differences in implementation (See Comparison of Amateur Radio DV by Roland Kraatz W9HPX.) All three of these are (arguably) open standards, allowing anyone to implement equipment that supports the standard. However, the reality is that D-STAR is still largely an ICOM system (with Kenwood joining the party), YSF is mostly a Yaesu system and DMR is…well, DMR is not deeply embraced by any large amateur radio equipment supplier. Instead, DMR is promoted heavily by Motorola for the commercial market via their MOTOTRBO product line. Another big factor is the availability of DMR radios from some of the low cost providers in the ham market: Connect Systems, Tytera MD-380. Baofeng has also announced a DMR radio but it has some potential shortcomings.

D-STAR has a clear head start versus the other DV standards and is well-entrenched across the US and around the world. DMR and YSF are the late comers that are quickly catching up. To put some numbers on the adoption of DV technology, I took at the digital repeater listings in the August issue of the SERA Repeater Journal. SERA is the coordinating body for Georgia, Kentucky, Mississippi, North Carolina, South Carolina, Tennessee, Virginia and West Virginia. This is a large region that includes rural and large urban areas, so perhaps it is a good proxy for the rest of the country. I just considered the listings for D-STAR, DMR and YSF repeaters, some of which are set up as mixed-mode analog and digital repeaters.

D-STAR   161    39%
DMR      136    33%
YSF      121    29%
Total:   418   100%
SERA Repeater Journal - August 2016

I was definitely surprised at how the DMR and YSF numbers are in the ballpark with D-STAR. Of course, we don’t know for sure how many of these repeaters are actually on the air or how many users are active on each one. Still, pretty impressive numbers. (And I did not bother to count the analog FM repeaters but those numbers are way higher, of course.)

It is the repeater clubs and repeater owners that drive the deployment of infrastructure for new technology. To some extent, they are driven by what their users want but also by their own technical interests and biases. One of the positive factors for DMR is that most of these systems are Motorola MOTOTRBO. Hams involved in commercial land mobile radio are exposed to that technology and naturally port it into the amateur radio world. MOTOTRBO is actually not that expensive and it’s built for commercial use. YSF received a big boost when Yaesu offered their repeater for $500 to clubs and owners that would put them on the air. By using Yaesu’s mixed analog/digital mode, it was an easy and attractive upgrade for aging repeater equipment.

Disruption From New Players

Early on in the world of D-STAR, the DV Dongle and DV Access Point by Robin AA4RC allowed hams to access the D-STAR network without needing a local repeater. This basic idea has continued and evolved in several different directions. For example, the DV4Mini is a cute little USB stick that implements a hot spot for…wait for it…D-STAR, DMR and YSF. This is very affordable technology (darn right cheap) that lets any ham develop his or her own local infrastructure. We don’t need no stinkin’ repeater. DV MEGA is another hot spot, supporting D-STAR, DMR and YSF. Oh, and then there’s openSPOT…don’t want to leave them out. I guess somebody forgot to tell these guys they have to choose one format and religiously support only that one.

dv4-mobile-transceiver
DV4 Mobile Transceiver as shown in Dayton 2016

OK, so that’s one way to solve the babel fish problem…support all three formats in one device. And that’s what the DV4 mobile radio promises to do as well: “This DV4mobile is a tri-band VHF/UHF transceiver (2m, 1.25m and 70cm) that supports DMR, D-STAR and C4FM ( or “fusion”) all in one box.” Heck, let’s throw in LTE while we are at it, it’s only software. This site says the radio will be available Q4 2016. Well, it’s Q4, so maybe it will be here soon.

Conclusions

So let’s wrap up Part 1 of this story. What can we conclude?

  • For the foreseeable future, we will have D-STAR, DMR and YSF technologies being used in amateur radio. I don’t see one of them dominating or any of them disappearing any time soon.
  • Equipment that handles all three of those DV modes will be highly desirable. It is the most obvious way to deal with the multiple formats. Software-defined radios will play a key role here.
  • A wild card here is DMR. It benefits from being a commercial land mobile standard, so high quality infrastructure equipment is available (both new and used gear). And DMR is being embraced by both land mobile providers (i.e., Motorola, Hytera) and suppliers of low cost radios (i.e., Tytera, Connect Systems). This combination may prove to be very powerful.