HamRadioNow: Digital Voice is EXPLODING (Click Bait #2)

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Episode 193:
Digital Voice is EXPLODING!
a update from David Rowe VK5DGR on
CODEC 2, FreeDV, and plans for a
disruptive VHF/UHF DV system


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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.

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.

[video=youtube_share;SmyVEwjhG_k]http://youtu.be/SmyVEwjhG_k[/video]
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Links:


David's Blog (details on FreeDV/CODEC2 development):
http://www.rowetel.com/blog/

Interview with David on "Linux in the Ham Shack"
http://lhspodcast.info/2015/01/lhs-episode-138-being-david-rowe/

David's 2011 talk on CODEC2 at the ARRL/TAPR DCC:
http://youtu.be/bLb7stxOqmI

The 2011 DCC's banquet talk - "The Village Telco" - David's project to provide extremely low cost telephone service in East Timore, Africa.
http://youtu.be/1H1OVH1FwTQ

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HAMRADIONOW.tv

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I'll reply to my own post... the repeater thing. I can see pretty much every HT and mobile having a "repeater mode." How much utility vs. how much potential for chaos? Could frequency coordinators handle the possibility of everyone turning on a repeater in their back yard, or driving down the road. Hmmm - Gary KN4AQ

(oh, and hey, QRZ.com: Wow! You had this thread up almost before I finished typing it. Thanks!) (Made a liar out of me over on AmateurRadio.com, though...)

 

The bait reeled me in- but YAAAWN ... 450bps eh? (50:40) so in the future DV hams on HF fone can look forward to sounding like Steven Hawking today.

Yup - "performance in fading channels" (51:40), "multipath" (53:50), "beat SSB at its own game" (52:05), BUT, "rules of physics: (53:00). And there was NO ANSWER OFFERED to the most strategic question asked - "DO WE WANT TO?" (52:53)

Negative SNR eh? Can't wait to hear HF DV in that DX'ped pileup! QhhhRrrrrZed? ... "He's spwit WUP! WUP !!"

However, attempted humor aside - I do respect the exploratory spirit and educational effort.

73 de John WØPV

 

Sorry, but I just can't get excited about digital SSB. I am left asking the question: WHY? Is there something wrong with SSB now? I don't think so.

I think digital modes are fine as long as they are the typical modes such as JT65, JT9, PSK, RTTY etc. that are in daily use here (my shack) and around the world. We don't need a mode that involves a way to torture a very effective and popular voice mode by twisting it into an unrecognizable signal on a standard SSB receiver with a nasal or squashed squeaky sound or a digital voice signal that keeps breaking up just for ------ ???? What? I'm left scratching my head here for words.

Experimentation is fine and that is what ham radio is all about but, just because we can do something, doesn't always mean we should.

Just MHO

K2WH

 

Oh yeah, we really need more repeaters. I'm sure you know the rest of the story so I won't go into it here.

K2WH

 

Ssb will never become popular because it makes everyone sound like Donald Duck.

Ad nauseum.

 

Got no use for DV as it stands but I'm totally digging the 'on channel repeater' concept.

 

On channel repeat has a lot of value. Every station that participate extends the range.

The larger a net becomes, the larger it can become, as each participating station extends the range.

An idle radio becomes a forwarder.

The problem I see is one of reflection. Solve that and you'll see vhf interest explode. Ad hoc propagation would be as mysterious and interesting as hf. And vhf qrp suddenly becomes viable for very long distances.

 

Great voice, Gary. I was a broadcaster and AM engineer in the late 60's and early 70's until I figured the real money was in the commercial field.. One thing though, man you have a spooky stare into camera. Try looking less right into the camera and smile more. Like me, you have a face made for radio....

Always enjoy the content. Thanks!

 

Another issue I see though is that people would want the ability to block people from using their station to do that. You get cliques in everything, including Ham Radio. They might not have a problem with their particular group using their idle radio to accomplish that, but maybe not the one over in the next town that they have some kind of "beef" with.

A shared system works if its truly shared by all, but I could see some people having an issue with their radio being able to be used by anyone for such a thing.

I'd also want to make sure the radio has something to detect high SWR to shutdown in this case-if the antenna suddenly falls over or something, the ability to shut itself down before it cooks itself would be a plus. Plus, I don't know how the FCC would handle such operation without operator intervention. Sure, stuff like APRS and packet exists, I suppose it would be treated like that with some kind of ID built into the packets, but still. Interesting can of worms.

But one thing I can do on my packet modem is deny connection by callsign if there is ever abuse or something like that. (Or for personal reasons, I suppose, since like a repeater operator, I can deny people the ability to repeat via my station if I so chose).

 

No more "EXPLODING" clickbait please! VHF-UHF DX'ing was supposed to "explode" with HEO SATS; look what happened to those! A REAL EXPLOSION!! Besides, at the pace of this vid it sounds more like IMPLODING to me; I will never get that time back ...

Which leads me to wonder about this "on channel repeat" feature. I don't know exactly what that may be but taken literally my guess its digipeating DV type signals. That is interesting, but my concern would not only be reflections, but "collisions", a pile up mess, and the latency or delays required to do many hops. Typical voice comm's are real time. Wouldn't the snooze factor waiting for DX to reply be like a duplex QSO with Mars?

 

collisions and latency are easily solved. digipeating to hop-count x would be no big deal. callsign lockout should be simple. its not my baby and haven't the skills to get involved but if i could i'd be all over it. consuming less bandwidth/power/resources are important to me. keeping a "mystery" aspect in radio is as well... if every station on freq and in range can forward, the band suddenly gets propagation and thats interesting.

those people who lack the capacity for sharing can just sit on 80m and pontificate like they always did. its not like they're up on 144.2 talking about a damned thing so no skin off their noses. if only the phone company would promote party lines.

 

I can envision and appreciate the draw of potential digipeated radiotelephone "propagation" on non-HF bands. But would still like to know a little bit about how the collisions and latency would actually be solved. Then I could pontificate about it too.

Getting back a bit more to the original thread topic about HF DV, consuming power and resources, compared to analog SSB, is also where that hits a roadblock for me.

SSB, generated with a well suppressed single carrier, is very energy efficient from the POV that without audio to transmit, the power level is ZERO. Not to mention that in a real on-the-air QSO, such pauses can be used to break in and operate in a more conversational pattern. (Or to squeeze in a quick call to a DX station ;-)

Yet with DV even when the op is silent the host signal is still blasting away with its plural carriers. This is seen in the waterfall display and rig meter on demo videos. The duty cycle for DV must be quite high in comparison to SSB. Eeeek.

Meanwhile, there is the still growing retro counter movement, putting the carriers back into HF double sideband, more popular every day especially, not just with heavy iron BA's but with SDR being applied to it. Spawning opportunities to work Hi-Fi DX up on 29 mhz.

 

This technology for use in amateur radio is in its infancy. I can speak to the fact in Public Safety that digital comms has been the standard for at least the last five or more years. Yes some agencies are stuck in yesteryear, but where I live the Charleston County Sheriffs Office was using 800 MHz digital around 5-6 years ago. And when you consider South Carolina is a wee bit behind times I am amazed it took this long for ham radio to get in the game. I would say in 12-18 months, with the way technology moves, this will be main stream. I'm not so much interested in the HF side but the VHF side. Instead of having say like 50 repeaters in the state, maybe we would only need 10. This would be tremendously important to all the amateur clubs to not have to spend on upkeep and maintenance.

 

If everybody has a repeater, WHO are they going to talk to? The one person they already talk to every day? Will people refuse to talk unless you come to their repeater? Or will they only allow their special friends to talk to them?

Anyway, as alluded to, there are tons of repeaters sitting idle doing nothing but IDs for days or weeks at a time. But a funny thing happens if you get people actually using them. If moderate to dead repeater suddenly gets a lot of new users -suppose a ham class finishes and everybody picks up some import radios and starts talking, etc. When that happens I have seen and heard the old timer users go bananas that their otherwise dormant repeater is suddenly busy.

So the problem of too many repeaters is not helped at all by this idea that nobody should use the stupid things. What the heck are they FOR anyway if nobody is going to use them? Ego? Wait, don't answer that. I already know.