Digital HF

[VK3NSA]

Hi,

I have been considering buying one of those AOR digital voice modems (http://www.aorusa.com/ard9800.html) for quite a while but I don't know if I'd have anyone to talk to on it. I'd be interested to know how many of you guys/gals are using them and if so what you think of them.

Cheers,
Steve VK3NSA

My website/podcast (http://web.mac.com/stephenjadams/Amateur_Radio_Beyond_the_exam/Home.html)

[n5rfx]

I have an ARD9000. With poor propagation conditions you may not be happy with it. Right now mine is used in the lab, and on the air regionally on 40 meters. I got two of them at Dayton in the flea market for less than what you would pay for one new. My buddy that was with me bought the other one from me.

You might want to try one of the PC Digital Voice packages. The audio is not nearly as good, but the price is right.

The N1SU (http://n1su.com/) site is helpful.

73,
Mark N5RFX

[N2RJ]

I use WinDRM from time to time.

[k5okc]

I have the original modem, and the little mobile one. I haven't used them in probably a year. They are easily jammed by nearby stations.

I did a test with an international broadcaster, and on a clear channel it worked all the way into the noise. On Ham bands, it is not good enough to interact with the crowded conditions.

My other pet peave, is that AOR has done nothing to update the firmware. The original modem supposedly does Phone, Image, and Data, but the data part is not worth anything, and I never bought the expensive memory board to enable the video.

I think it's too expensive new, so I would look for an used one. I can sell you my original one if you're interested. It might take me a few days to find all the cables and booklet http://www.qrz.com/iB_html/non-cgi/emoticons/smile.gif

Steve

[WA3KYY]

Quote[/b] (k5okc @ Dec. 07 2007,16:06)]I have the original modem, and the little mobile one. #I haven't used them in probably a year. #They are easily jammed by nearby stations.

I did a test with an international broadcaster, and on a clear channel it worked all the way into the noise. #On Ham bands, it is not good enough to interact with the crowded conditions.
And there Steve is the crux of the issue as to why digital is a specialty niche in amateur radio while a large percentage of the rest of the communications world has switched to digital. #

If you have a dedicated clear channel free of on and adjacent frequency signals, digital works well down into the noise. #Rarely are such conditions found on amateur HF frequencies and are likely to continue to be rarely found. #Even more so as Cycle 24 ramps up and the bands become even more crowded then they are now.

Until a digital mode is devised that can successfully operate under typical amateur HF conditions, analog modes will dominate.

73,
Mike WA3KYY

edited to remove numerous typos due to trying to have my fingers keep up with my thoughts.

[VK3NSA]

Sounds like its not that great. I also found a link to sample audio and it sounds a bit robotic for me. If it worked well under adverse conditions then maybe it would be worth the $&%@ sounding audio.

Steve VK3NSA

[k0dxc]

well im sure not

[k5okc]

Quote[/b] (VK3NSA @ Dec. 07 2007,16:35)]Sounds like its not that great. I also found a link to sample audio and it sounds a bit robotic for me. If it worked well under adverse conditions then maybe it would be worth the $&%@ sounding audio.

Steve VK3NSA
It was pretty amazing the first couple of QSO's, but the band conditions and few users available that it was frustrating.

Some people have tried it on VHF mobile, and it doesn't work well for that either. One reported that it worked if he was stopped, but not if he was moving.

I've only used it on HF. Since it is a data and phone modem (the first model) you can use it on 30 metres here in North America, but again, band conditions were poor the last few years.

I suspect it will be pretty popular when the bands open up. I'd like to try it on 10 metres FM.

[N0NB]

I played with WinDRM running under Wine about a year ago. Most likely due to my low wire antenna, poor band conditions, or both, I would get bits and pieces of audio on 20m. I tried receiving pictures on 75m and never did get that to work as the multi-path or selective fading seemed to kill it.

Digital voice on the amateur HF bands will require a unique approach, in my estimation. It seems to me that current digital technology is designed to be one way, from a high powered transmitter to receivers. Amateur communication is typically low power to low power and doesn't often have the benefit of high a S/N ratio both ways. The shared frequency nature of amateur radio creates another technical hurdle with our overlapping signals, something operators learn to deal with.

I think it will be interesting to watch digital voice develop and I may find myself playing with it one of these days.

[VK3NSA]

Quote[/b] (k5okc @ Dec. 07 2007,14:55)]Quote[/b] (VK3NSA @ Dec. 07 2007,16:35)]Sounds like its not that great. I also found a link to sample audio and it sounds a bit robotic for me. If it worked well under adverse conditions then maybe it would be worth the $&%@ sounding audio.

Steve VK3NSA
It was pretty amazing the first couple of QSO's, but the band conditions and few users available that it was frustrating.

Some people have tried it on VHF mobile, and it doesn't work well for that either. #One reported that it worked if he was stopped, but not if he was moving.

I've only used it on HF. #Since it is a data and phone modem (the first model) you can use it on 30 metres here in North America, but again, band conditions were poor the last few years.

I suspect it will be pretty popular when the bands open up. #I'd like to try it on 10 metres FM.
Hi,

Just wondering what the advantage would be in using it on FM. It doesn't make sense to me.

Steve

[k5okc]

Quote[/b] (VK3NSA @ Dec. 08 2007,03:56)]Just wondering what the advantage would be in using it on FM. It doesn't make sense to me.
The modem is designed to work with SSB and FM, but with FM, you can turn off the AFC control. In SSB you need the AFC on to track the signal. I think you can use a shorter preamble as well. You need about a 1.5 second preamble tones on SSB every time you key the Mic.

I have no experiance using it on 10 FM, so I'm thinking it might be interesting compared to SSB. I don't know if it would be an advantage. Maybe not...

[KG4RUL]

Another solution desperately looking for a problem!

[k5okc]

Quote[/b] (KG4RUL @ Dec. 08 2007,11:17)]Another solution desperately looking for a problem!
Right... CW is the only way to go...