HF DV:
Greg.Eubank@...
Do you have any plans for or is anyone presently working on an HF DV application?
73's
- Greg –
KL7EV
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Hi Greg, The primary amateur radio DV applications on HF are D-STAR (http://hf.dstar-relay.net) and Codec2. The UDRC II is a candidate to support a Codec2 HF modem/controller. I think there are people interested in doing this. The UDRC II plus a ThumbDV could be the basis of an HF D-STAR modem/controller/AMBE encoder/decoder but an application is needed. Do you have a particular application in mind?
On Thu, Mar 16, 2017 at 2:05 PM, Eubank, Greg (MVA) <Greg.Eubank@...> wrote:
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Stuart Longland VK4MSL
On 17/03/17 07:05, Eubank, Greg (MVA) wrote:
Do you have any plans for or is anyone presently working on an HF DVYou mean like this? http://www.freedv.org/ -- Stuart Longland (aka Redhatter, VK4MSL) I haven't lost my mind... ...it's backed up on a tape somewhere.
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Eubank, Greg (MVA) <Greg.Eubank@...>
We have the Alaska Pacific Net (Alaska Emergency Preparedness Net) and also 60 Meters where we are blessed to experience increased noise floor conditions and I am hoping to establish an HF DV voice net that we can use to communicate during these challenging communications conditions.
I’ve been following the ongoing announcements for the UDRC and PiDV/ThumbDV products and I feel it is about time for me to stop following and start moving!
I see the opportunity to expand this technology to the Emergency Management and Disaster Preparedness community if we can come up with a simple and effective turnkey solution.
Does anybody on the forum know of anybody incorporating this into the Amateur HF ALE Network? I’d be interested in experimenting with this using my Micom ALE radio.
73's
- Greg –
KL7EV
From: John D Hays - K7VE [mailto:john@...]
Sent: Thursday, March 16, 2017 13:29 To: main@nw-digital-radio.groups.io Subject: Re: [nw-digital-radio] HF DV:
Hi Greg,
The primary amateur radio DV applications on HF are D-STAR (http://hf.dstar-relay.net) and Codec2.
The UDRC II is a candidate to support a Codec2 HF modem/controller. I think there are people interested in doing this.
The UDRC II plus a ThumbDV could be the basis of an HF D-STAR modem/controller/AMBE encoder/decoder but an application is needed.
Do you have a particular application in mind?
On Thu, Mar 16, 2017 at 2:05 PM, Eubank, Greg (MVA) <Greg.Eubank@...> wrote: Do you have any plans for or is anyone presently working on an HF DV application?
73's
- Greg –
KL7EV
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Brad NK8J <bradnk8j@...>
Freedv for voice or with icom dv (digital voice) dstar on HF
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On Thu, Mar 16, 2017, 5:21 PM Eubank, Greg (MVA) <Greg.Eubank@...> wrote:
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Andrew O'Brien
While I would like this to succeed, the SNR required for digital voice on most HF bands is such that it renders DV as only useful between stations with a lot of power and/or really high gain antennas. Thus, use for Emcomm would be not widely adopted. IF software for HF DV use allowed access of an HF user into things like Dstar reflectors or call routing, that WOULD be useful for emcomm. Andy K3UK
On Thu, Mar 16, 2017 at 8:08 PM, Brad NK8J <bradnk8j@...> wrote: Freedv for voice or with icom dv (digital voice) dstar on HF --
Andy
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I don't know that HF DV would have a value added for emcomm but FreeDV 700C is a new mode and I have heard it work when the waterfall was barely visible. The authors claim low SNR performance rivaling that of low signal level SSB. i agree with Andrew in general using previous digital modes, but if 700C indeed performs as claimed, that view may now outdated. jeff
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Curt Mills, WE7U
On Fri, 17 Mar 2017, bauerjv@mac.com wrote:
I don't know that HF DV would have a value added for emcomm but FreeDV 700C is a new mode and I have heard it work when the waterfall was barely visible. The authors claim low SNR performance rivaling that of low signal level SSB.Note that Codec2 is still being worked on and has several modes with different bit-rates. It may be too early yet to look for a solid implementation you can depend on for emcomm use. -- Curt, WE7U. http://we7u.wetnet.net APRS Wiki: http://info.aprs.net/
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On 17/03/2017 11:17 PM, bauerjv@mac.com wrote:
700C is under development, with the goal to equal or exceed the performance of SSB on HF channels. It is getting closer to that goal all the time. Latest results on non fading channels look pretty impressive. -- 73 de Tony VK3JED/VK3IRL http://vkradio.com
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Stuart Longland VK4MSL
On 17/03/17 20:54, Andrew O'Brien wrote:
While I would like this to succeed, the SNR required for digital voiceWell, this can be true of other systems like FM too. 1200 baud AFSK over FM is actually pretty terrible as a modem in performance. http://www.rowetel.com/?p=3799 is written by the Codec2 author, thus might be seen by some as biassed, but in that, he analyses the AFSK/FM set-up typically used in packet and assesses its theoretical performance. The results were not great. It was built that way because people made use of what they had at the time, old Bell modems. It works well enough for most purposes, but it was never a stellar performer. Typically you need decent transmit power or high-gain antennas to make it work well. Yet, it is used a lot in emcomms. The saving grace is that the packet typically only needs a short burst of a few seconds to transmit a longish sentence that would take about 30 seconds to read out. So you can afford high power because the duty cycle is much lower. DV would take away that gain, but then again it can be recorded, transmitted with stronger FEC and stored for playback later, so if the operator is distracted, the message will still be there waiting for them when they get back to the radio. This is a trick that analogue voice is unlikely to pull off. As for FreeDV and D-Star HF; transceivers for both do have the advantage that if conditions get bad, it is a single button press usually to switch to SSB. Another button press and it's to CW. Or with a device like the UDRC, we can use PSK-31, etc. This is feature of amateur emcomms that we can switch and adapt as the conditions require. Commercial radios do not give their users the same luxury. Procedure can dictate how you go about switching modes. Our strength in emcomm is that we have all these modes at our disposal, and if one stops working, we can switch modes. This is less risky than switching frequencies, and you get to know digital modes by ear and most applications feature a waterfall. The application can pass through the analogue audio when there's no decodable signal anyway, so in that case the fall-back to SSB is automatic. A smarter application could be watching for PSK-31, slow CW, WSPR and DV, etc, and dynamically switch between them on receive, so the only decision an operator is making is what to use when transmitting, knowing the other end will figure out how to receive the message. It'd be difficult to pack this into a hand-held, although with single-board computers like the Raspberry Pi compute module, which could be paired up with the TLV320AIC3204 in a UDRC-compatible package that could conceivably fit inside a hand-held radio built for it. However, hand-helds seldom reach below 50MHz (I'll ignore 27MHz), and it is HF we're discussing here, where we can likely afford a bit more computing power to do such real-time processing as we can afford the slightly bigger form factor computers that would provide the necessary grunt. In short, I think it is premature to discount HF DV for emergency comms. It's no silver bullet, but rather, yet another tool in getting a message through. -- Stuart Longland (aka Redhatter, VK4MSL) I haven't lost my mind... ...it's backed up on a tape somewhere.
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Eubank, Greg (MVA) <Greg.Eubank@...>
My initial thoughts are, that if there was a DV implementation that utilized Pactor Error detection and correction technology, that an HF DV protocol could theoretically be designed to provide similar performance of the Pactor method for Modulation/Demodulation.
From: Andrew O'Brien [mailto:andrewobrie@...]
Sent: Friday, March 17, 2017 02:55 To: main@nw-digital-radio.groups.io Subject: Re: [nw-digital-radio] HF DV:
While I would like this to succeed, the SNR required for digital voice on most HF bands is such that it renders DV as only useful between stations with a lot of power and/or really high gain antennas. Thus, use for Emcomm would be not widely adopted. IF software for HF DV use allowed access of an HF user into things like Dstar reflectors or call routing, that WOULD be useful for emcomm. Andy K3UK
On Thu, Mar 16, 2017 at 8:08 PM, Brad NK8J <bradnk8j@...> wrote: Freedv for voice or with icom dv (digital voice) dstar on HF On Thu, Mar 16, 2017, 5:21 PM Eubank, Greg (MVA) <Greg.Eubank@...> wrote:
-- Andy
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Stuart Longland VK4MSL
On 18/03/17 11:20, Eubank, Greg (MVA) wrote:
My initial thoughts are, that if there was a DV implementation thathttps://en.wikipedia.org/wiki/PACTOR seems to suggest you'll have to sweet-talk SCS into making a software version of their (proprietary) modem to run on Linux/armhf. I wish you luck. It is worth noting that DV is a very different beast to data. Audio delivery is hard real-time. If each character of this email was delivered with a random 1-3 second delay… it would be annoying to watch but not harmful to the intelligibility of the message. However, if a burst of no --- i --- se --- ca --- used delays playing back parts of an audio recording… this discontinuity of playback is disastrous. The broken-up signal cannot be understood, even though no audio samples have been lost, the human brain cannot process the parts in this disassembled manner. Data modems are intended on getting a packet of data from A to B *perfectly*. A single bit error means the data at the other end is corrupt and therefore useless. So they achieve lower BER by long synchronisation runs and lots of FEC. Voice modems are intended for constant data rate, and will generally produce a higher BER, but can synchronise very quickly, thus will handle sudden loss and return of signal better. -- Stuart Longland (aka Redhatter, VK4MSL) I haven't lost my mind... ...it's backed up on a tape somewhere.
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Richard - VE7CVS
Actually, 1200 bps over FM has a lot of redundancy that makes it work well in most conditions (if properly configured) - it's just not a very efficient use of bandwidth!
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I implemented some of the very first Bell 202 modems for packet radio back in 1979. That 'standard' that you see know comes from the VADCG (Vancouver Amateur Digital Communications Group), we got a stack of Bell 202-standard modems from the Canadian Imperial Bank of Commerce for a whopping $1.75 each - we bought them by the pound! The idea was to come up with a cheap, easy-to-implement-with-existing-2m-rigs modulation scheme - radios of that day were notoriously poor for digital radio, I modified ICOM IC22-U and IC22-S radios to bring their squelch detect down from several hundred to several tens of milliseconds - and other radios were even worse, some of the early synthesised rigs took forever to stabilise. Some of the squelch mods, and the 9-pin plug wiring standards for ICOM rigs came from me (although I was totally oblivious that I was creating anything resembling a 'standard'...). Modern radios can do 1200 bps with relative ease. It's still terribly slow, we at the VADCG saw 1200 bps as a stopgap until we could bring out fast, 220 MHz radios. Unfortunately, we never got that far. :( Another group that I belonged to in Vancouver brought out a very sturdy 56 kbps standard system (Dennis Rosenauer was the main instigator - and stellar RF engineer - for this system - for Dennis, 70 cm 'is DC' :-) - Richard
On 3/17/17 4:12 PM, Stuart Longland VK4MSL wrote:
On 17/03/17 20:54, Andrew O'Brien wrote:Well, this can be true of other systems like FM too. 1200 baud AFSKWhile I would like this to succeed, the SNR required for digital voice
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