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Author Topic: Why is there no digtial voice on HF.  (Read 4005 times)
OLDWORLDER
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Posts: 20




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« on: May 22, 2011, 10:15:23 PM »

If the opperating bandwidth of digital modes is as narrow as I have read, then why has it not been implemented on HF where bandwidth isn't as easy to come by. 
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AA4PB
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Posts: 12769




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« Reply #1 on: May 23, 2011, 07:16:37 AM »

The bandwidth of a digital signal depends on the data rate. Doing real time streaming digital voice requires far more bandwidth than sending characters at a typing rate as in PSK31 or even RTTY. The result is that there is no great bandwidth benefit to using real time digital voice over analog SSB.

There is currently some digital voice being used on HF. The biggest issue is that you must be tuned to the exact frequency at the beginning of a transmission in order to properly synchronize and decode the digital voice signal. The result is that most people make the initial contact with SSB and then switch to digital voice. Its fun to experiment with but it in its current state it doesn't seem to be very practical for general HF amateur use unless we eliminate the VFO and go to a channelized arrangement.
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G0GQK
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Posts: 634




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« Reply #2 on: May 23, 2011, 01:51:22 PM »

Like everything else which doesn't catch on, nobody is interested.

G0GQK
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VA7CPC
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Posts: 2371




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« Reply #3 on: May 23, 2011, 04:59:38 PM »

One more reason:

. . . With good signal-to-noise ratios, digital voice works well.  But with marginal S/N ratios,
. . . digital voice _doesn't work at all_. 

The received signal doesn't degrade "gracefully" -- it rapidly becomes completely unreadable.

I don't know how much the shortwave broadcasters have been using the shortwave digital standard, DRM (digital radio mondiale, I think).  They would run into the same problems as hams.

              Charles
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KQ4KK
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Posts: 18




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« Reply #4 on: May 24, 2011, 03:10:23 PM »

As I understand it, the new ICOM 9100 does DSTAR on 10m and 6m. And "it can do DSTAR on other bands as well". Since DSTAR is a form of FM, it fits in the FM portion of 10m and 6m.
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KS2G
Member

Posts: 389




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« Reply #5 on: May 24, 2011, 03:41:51 PM »

Digital Voice Amateur Radio Association:
http://www.dvara.org/

Read-up on the AOR system for digital voice on HF.
Hear it demonstrated at Dayton a few years back.
VERY impressive.

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N0SYA
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Posts: 354




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« Reply #6 on: May 25, 2011, 11:57:58 AM »

Hi
There are/were efforts to do digi voice in a 500Hz bw, and it would be here but for lack of a codec. Unlike the digi voice hams have today that requires a decent sn ratio, this one is/was for dxing.
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If you have a clumsy child, you make them wear a helmet. If you have death prone children, you keep a few clones of them in your lab.
KC2UGV
Member

Posts: 383




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« Reply #7 on: May 31, 2011, 11:57:39 AM »

Hi
There are/were efforts to do digi voice in a 500Hz bw, and it would be here but for lack of a codec. Unlike the digi voice hams have today that requires a decent sn ratio, this one is/was for dxing.

To echo this, a lack of vocoder is an issue.  Lots of work being done on Codec2, however it's targeted as an AMBE2020 replacement.  Work is underway to get it to work for HF as well.
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W0JAB
Member

Posts: 19




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« Reply #8 on: June 02, 2011, 10:54:28 AM »

Try this list to help you set up a QSO or to find
help with this mode.

One afternoon while driving I-70 in the center of Missouri
I worked a ZL station.

  http://groups.yahoo.com/group/ARD9800/

John, W0JAB
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STAYVERTICAL
Member

Posts: 854




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« Reply #9 on: June 06, 2011, 04:22:48 AM »

I think the answer to this question is not so much technical than sociological.
It is the same reason that you will find many more people on PSK31 than Olivia for example, or that many more people use PC platforms than Macs.
Once a technology gets a certain critical mass of users, success builds on success and the greater number of users will attract even more users, resulting in a snowball effect.
Although I love Olivia, and am continually astounded at how well it decodes weak signals, I find it difficult to consistently get QSO's on this mode. Granted, there is a small group of enthusiasts, but for consistent QSO ability, I find myself heading back to PSK31.
Digital voice is in the same category as exotic digital modes - the technology works, but suffers from lack of a consistent user base.
It is no more difficult to run most exotic digital modes than ticking a box on the PC screen, so it is not the technology which is the problem. Having to arrange qso's or join a net to try to qso is an interesting transient exercise, but will restrict the number of participants even further.
In my experience, ham radio is definitely stratified into layers of users who tend to remain with certain modes.
A large number of my SSB voice contacts have never tried digital modes, nor are they particularly interested in them. And many digimodes operators have forgotten where they stored their microphone! This is not not a criticism, but just a reflection of an activity which is after all a hobby, and as such, should cater to the particular individuals interests.
Digital voice is in the situation of falling between SSB operators who dont see the advantage of the extra complexity, and digital operators who are more interested in typing than talking.
Vive le difference!
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KC2UGV
Member

Posts: 383




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« Reply #10 on: June 06, 2011, 08:38:41 AM »

...clip...
And many digimodes operators have forgotten where they stored their microphone!
...clip...


I think I fall in this boat lol
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N1ZHE
Member

Posts: 68




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« Reply #11 on: October 10, 2011, 09:33:21 AM »

$340.00 to $540.00 to get started is my main reason for not using it.

I believe it would even be legal on 30 meters because it is a digital mode.
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