HamRadioNow: Digial Voice is EXPLODING! (Click Bait #2?)

First, I apologize for this cut-and-paste from QRZ.com. I won’t usually do that, but I spent a lot of time writing this, and I want to spread it around. They moderate, I’ve been “pre-approved” here on AR.com, so you’ll see it first. So I guess I “cut and pasted” from here to there. OK, I can live with that…

HamRadioNow Episode 193: DV is Exploding

David Rowe VK5DGR updates CODEC2 and FreeDV,
introduces a FreeDV “Speaker-Mic”, and is developing a
disruptive DV system for VHF/UHF

David Rowe VK5DGR is the ham who developed CODEC2*, and CODEC2 changes everything. So, is this a click-bait title, or a valid prediction?

In this program, David talks to me about the SM-1000 “speaker-mic”, a little box he’s developed to let hams use FreeDV digital voice without a computer. The box does all the processing and has all the input/output connections, so you can run digital voice over your SSB radio with no computer attached. The SM-1000 will be available soon for about $200.

We also talk about improvements to FreeDV and CODEC2 that David expects will make digital voice work as well as, and maybe a little better than SSB with weak signals or noisy HF conditions. Today, SSB can be copied below the level that a DV signal drops out, but it’s somewhat rough listening. Yesterday, you needed a lot more signal for DV. Tomorrow: parity with SSB, or maybe advantage: DV. Yes, there are plenty of issues left. Voice quality (many hams don’t like the ‘robotic’ sound or the fidelity). Contest/DX pileups. David readily admits that SSB has been around for so long on HF because it works great in that hostile environment. He sees it as a challenge.

Finally, David tells me about a VHF/UHF project he’s working that, at my first look, has the potential to disrupt everything in repeaters. It won’t happen overnight, and given ham’s investment in analog FM and even the newer DV modes from D-STAR to DMR and Fusion, it might not really happen at all. But here’s what David is aiming at:

  • Signal to Noise that’s better than FM by 10 dB
  • 5 kHz bandwidth
  • TDMA “time-slice” modulation that will allow for “on-channel” repeaters.

By “on-channel” I mean repeaters that don’t need an “input” channel. As David described it, the repeater receives you for about 40 milliseconds, then retransmits what it just received. When you’re transmitting, your radio transmits for the 40 ms that the repeater is receiving, then stops while the repeater transmits. When you’re receiving, the software smooths it all out so it sounds like a continuous transmission. David didn’t say this, but I suppose it would allow you to monitor your signal thru the repeater in real time. This also means that a repeater works without a duplexer, and without some of the shielding needed to allow a high-power transmitter to operate right next to a sensitive receiver.

The disruptive part, though, is the 5 kHz bandwidth and no separate receive frequency. Cheaper, better repeaters that use far less spectrum will allow for dozens more repeaters to go unused everywhere. OK, that’s a snarky reference to the common complaint about unused repeaters in ham radio, but in commercial and public safety, where spectrum is in extreme demand, it really could change everything. And they have money.

David says that he needs to develop hardware for this because current hardware won’t handle the DV signal to make this work. His time-frame for a working prototype: end of this year. And his vision is a repeater that’s as simple as “an HT you stick up on the hill.” You might want something a bit more robust for your full-time repeater, but for fast emergency use… wow. On the other hand, I can see every DV mobile and HT having a “repeater” mode built-in. I see equal potential for utility and chaos on our VHF/UHF bands! Would we be up to the challenge?

Yes, DMR/MotoTRBO uses TDMA. They don’t use it for on-channel repeaters. They use it to allow two simultaneous conversations to occupy a single RF channel, but it still needs an input and an output frequency (and a duplexer), and occupies 12.5 kHz of RF bandwidth.

So, watch the show, and see the future…

*CODEC2 is the open-source software that digitizes speech into a very narrow, or slow, stream of data. The result: a highly useful, if a bit “robotic” sounding version of your voice that can be sent over a typical SSB transmitter, but using about half the RF bandwidth of typical SSB speech (2.5 kHz for SSB, 1.2 kHz for the DV). David’s been working on it for about 5 years, and he’s far from done. It works very well today. It’ll work even better tomorrow. Did I mention it’s open-source? Yes, there are proprietary codecs that do this. The AMBE codecs used by D-STAR, DMR and Fusion are the most common today. Is CODEC2 better? I’ll leave the technical arguments to those with the chops to make them. None of them are done. They’re all being improved. CODEC2 is free, and the hardware that uses it, typically SDR like FlexRadio, can be updated as new versions are released.


David’s Blog (details on FreeDV/CODEC2 development):

Interview with David on “Linux in the Ham Shack”

David’s 2011 talk on CODEC2 at the ARRL/TAPR DCC:

The 2011 DCC’s banquet talk – “The Village Telco” – David’s project to provide extremely low cost telephone service in East Timore, Africa.

Gary Pearce, KN4AQ, is the host of HamRadioNow.tv. If you enjoy this and other HamRadioNow programs, help keep them 'on the air' with a contribution. Contact him at [email protected].

5 Responses to “HamRadioNow: Digial Voice is EXPLODING! (Click Bait #2?)”

  • Ricardo EA4GMZ:

    Digital voice will be successfull when it allows new services such as routing calls or texting. Making a simple qso in digital instead of analog offers no great interest. I think that is the reason why dv is still marginal.

  • Hans (BX2ABT):

    Ricardo, DV on the HF bands is still marginal because it is unchartered territory. The FreeDV guys are doing a terrific job of creating a codec that can be used reliably under very difficult circumstances on HF. It makes DV on VHF and above look rather tame and boring, although I don’t dispute it has its place. Integration with other services will always be possible when the system is ready for production. The FreeDV people are also making it easy to enter easily by building add-on equipment. With this new FreeDV box you can start playing with your existing equipment instead of buying a new – expensive – rig. And the biggest plus is that is is open source, so tinkerers can play with it without limitations. This will encourage development on a full scale not partial, like a popular other DV option from a big manufacturer.

  • Harry K7ZOV:

    If DV is as good as digital TV that replaced analog TV it will be a giant step backwards. When I was in TX my mother in law had her son put up a TV antenna so she could cut the cord with DISH TV. Well it rained..a lot… The signal keep cutting out and breaking the picture up and lock up the TV while it did a re-sync. This went on for weeks. Then I went to my Brother in laws place for dinner a couple nights. He has DISH… Guess what? YUP his Digital picture was cutting out.. Fast forward. Here in the White Mountains of AZ Cable-One has cut ALL analog from the high speed cable and gave use free HDTV digital converter/interface boxs. Pictures are outstanding…However one box keep loosing signal strength,being on the other side of the house and that TV cuts out…Also the main setup next to the TV when the weather is bad cuts out.

    What I am stating is with analog this cutting out and dropping would never happened. A good solid signal into a digital setup, including DV, will probably be great. But reality sucks in RF. Killowatt stations, QRM, QRN, QSB, LIDS all will cause digital bits to drop and in the end a poor QSO.

    Maybe FMDV will survive…But my feeling is that SSB DV is just plane stupid and will always be plagued with issues… IMHO

    nickles worth of rant… Take it or leave it…Just the way I see it and with 40 yrs in electronics and most being in the digital world that is what I am basing this on.

    73 Harry K7ZOV

  • Gary Pearce KN4AQ:

    Harry K7ZOV says “Maybe FMDV will survive…But my feeling is that SSB DV is just plane stupid and will always be plagued with issues… IMHO”

    Wow. Will always be plagued with issues.

    1st… Harry, did you listen to David?

    2nd… David, give up. It’s just plane (sic) stupid. All is lost.

    I’m reminded of John Belushi’s rant in Animal House. “Was it over when the Germans bombed Pearl Harbor? Hell no!” (Forget it, he’s rolling). OK, I looked it up, and it wasn’t exactly what I remembered, but you get the point. To say something in technology will never work is… what’s the phrase I’m looking for… oh, yeah… just plane stupid.

    By the way, DISH video is subject to rain fade because of the frequency, not the mode. I remember sitting in Master Control at NBC’s WMAQ-TV in Chicago as the engineer on duty watched the RADAR show a storm approaching the studio. NBC used Ku band (as DISH does) for their network feed, with a C-BAND backup. The red blob of heavy rain approached the station’s dish location, and we heard it on the roof. The engineer’s finger hovered over the button that would switch the network signal from the primary Ku receiver to the C-band receiver. “annnnd…. NOW”. It was a game he’d mastered. Just as he punched the button, the monitor for the Ku band signal went to snow.

    Yes, it was analog. Not digital. This was 1988.

    I’m thinking of a new tag line for our hobby: Amateur Radio – allowing people to live in the past since 1912.

  • Matt W1MST:

    Reminds me of a saying we have in the fire service:

    “A century of tradition unimpeded by progress.”

    Works for ham radio, too!

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