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HamRadioNow: Digial Voice is EXPLODING! (Click Bait #2?)
March 4th, 2015 | 
Author: 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.
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
UK Activity Contests
Every Tuesday evening the RSGB organises a VHF/UHF activity contest. I have just in time submitted my entry for the low power section of last Tuesday evenings 50MHz contest. With just 3 QSOs logged there is no way on this earth that I’ll be anywhere but near the bottom! Having a V2000 omni vertical antenna, 5W, and a stroke damaged voice is no way to enter a 50MHz, UK based, contest! The V2000 and even 2.5W is great in the Es season (I work most that is around), but it is far from ideal working inter-G on 6m SSB.
Tonight is the 144MHz (2m) March leg of the UKAC. My small 3el beam should turn again now (manually) so I’ll see how long my voice holds out. 45 minutes to 60 minutes is usually my limit. Last week I was on very little time. My best DX seems to be around 200km with 5W on 2m in “normal” conditions.
At this time of the year there are fewer portable stations active but activity (SSB and CW) is usually very high so this is a good opportunity to work some new squares. People have been very friendly. If in the UK or nearby join the fun 2000-2230z on 2m. I usually go QRT by 2100z because of the strain on my voice.
Just checked where I sit in the Jan 2015 AL section of the 50MHz UKAC. You guessed? Bottom! Well someone has to be!
Austin Amateur Radio Supply Closes
Texas amateur radio equipment distributor Austin Amateur Radio Supply has closed its doors.
Started by Johnny Paul, WA5BGO, SK, over 35 years ago, Austin Amateur Radio Supply had been a regular advertiser in the major ham publications. After Paul’s death in late 2013, Austin Amateur Radio continued operation for well over a year.
I bought my first HT from Austin Amateur Radio Supply 25 years ago. It’s always sad to see another small retailer close their doors.
Thank you to the Paul family for 35 years of service to our community. You are missed already.
10GHz WBFM transceivers
The modern way of getting (simply) into 10GHz WBFM appears to be using very low cost 10GHz Doppler radar modules with a 100MHz FM receiver. Whilst with G6ALB for my Pixie tests Andrew demonstrated a working 10GHz link based on these low cost modules. These are useful links Andrew sent me.
Hi Roger,These are the units I found when I was looking for [definitions of] the 10.525 GHz ISM band.It looks like 3cm Doppler radar is alive and well,I’d assumed it had disappeared in favour of PIR.Some data here:These are very good pages (for wideband FM on 10 GHz).
Andrew G6ALB
40m Pixie measurements
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| Pixie harmonic measurements |
This afternoon I visited G6ALB to do some more accurate measurements of my completed 40m Pixie kit. Power out with the 12V battery was 400mW and with a fresh PP3 9V battery 200mW. On the 12V battery TX current is around 129mA and at 9V around 83mA. 2nd harmonic rejection was about 20dB. Even the 9V output is a useful level. Maybe the cased unit should include an internal 9V battery pack which is switched off when an external 12V pack is available?
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| Pixie on the bench |
To be more useful, I should add a 7.030MHz crystal and have a switch to select this or the original 7.023MHz one. 7.030MHz is the QRP frequency. My experience is this can be quite busy.
I should also case the unit! Drilling the case could be a challenge in my current state of health! Just doing the building and testing was exhausting.
What’s the difference between the Baofeng UV-3R, UV-5R, UV-82, UV-B5/UV-B6, etc.?
In China, there is a lot of passing around of designs, tweaking, improving upon, and re-branding.
In 2011 a company called VeroTelecom brought out a “UV-3R” radio which was picked up on by Baofeng and brought to a Western market where, eager for a bargain, it went down a storm. A year later, TYT made the TH-UV5R which again was picked up by BF and released in the West as the UV-5R. Initially meant as cheap SDR business band HTs, hams quickly noticed that they have a proper VFO making them perfect for our uses.
A year after that, Baofeng (now Pofung, internationally) designed and released their own radios based on the UV-5R; the UV-82, a more “professional” version of the UV-5R, and the UV-B5/UV-B6 with an entirely redesigned and far more selective RF front-end.
The first two are pants as radios go, with all kinds of weird bugs, overloading problems, and less-than-adequate phase noise and harmonic suppression performance.
The UV-82 crossed the line from “meh” into “good” with performance being on par with existing radios twice the price.
The UV-B5 blew all existing Baofengs out of the water, with on-air performance nearly matching that of Yaesu’s lower end Vertex (VX-**) series handhelds which cost five times the price. It has its quirks but for basic repeater ragchewing its value for money can’t be beaten.
The great thing is, all these radios can be had for under $35 if you know where to look: while not perfect they are a great way to get started, or to dip your toes into the hobby without spending too much. However, if you have the disposable income to put down on a more expensive radio, do – the Yaesu FT-60R is a good start.
If you’d like to read more about the differences between some of these radios, I go into a little more detail here.
First 40m Pixie QSO
At 1000z this morning I exchanged RST 579 reports with G6ALB who is 3km from me on my 40m Pixie on 7.023MHz CW. This was my first on-air QSO. Netting was perfect and I used the rig directly into my low Par triband antenna. An ATU might have helped. Andrew G6ALB said the channel was pretty busy but that I was a good RST579 with no hint of chirp. This afternoon we’ll put the rig on his spectrum analyser. I gave Andrew 579 probably reflecting the poorer MDS of the Pixie. I have no idea of his power or antenna.
My initial goals have been met: I built the kit and have managed a QSO on the air with it. With the fatigue associated with my brain bleed still very apparent (I am well and truly shattered currently), I was well pleased. A few more QSOs with the 40m Pixie would be good, HI.
$10 well spent. Excellent little kit. FB little transceiver. Works surprisingly well.
