--- In digitalradio@yahoogroups.com, "Andrew O'Brien" <[EMAIL PROTECTED]> wrote: > > I have been "QRV" on digital voice ,using WinDRM, and thought I would offer > some rookie/newbie random thoughts. > > 1. This mode's performance may appear counter-intuitive for most digital > mode operators. By that I mean, we associate digital modes like PSK31, > Olivia, MT63, etc, with the ability to communicate under weak signal > conditions. To be able to communicate when SSB analog voice signals are not > reliable. > > It is the opposite with Digital Voice , as manifested in WinDRM. Perfectly > copyable CW and traditional SSB voice signals do not translate in to enough > signal to maintain the digital voice transmissions. e.g. my analog QSO > today with Gerhard OE3GBB was about a 449 RST. That is; Readable with > practically no difficulty, Fair signals . However, I had to focus my brain > quite a bit to pick his voice out between the QRM. When we switched to DV, > the audio was stunning in quality (better than FM on 2M) but I only copied > about 40% of what he sent, the rest was just silence. So, I am not sure > what "use" this communication method has if we need "good" signals rather > than fair or weak signals. If one can copy a person fair to well with SSB > analog, why do we need to switch to DV voice? > > > 2. The software (WinDRM) is very well designed and fairly easy to figure > out. The ability to have the software switch Mic/Line In settings in the > sound mixer is very useful. The waterfall and other tuning display > indicators are extremely well thought out. > > > 3. There is something "odd" about copying HF signals with good audio > fidelity. My old ham brain is so used to "Donald Duck" under water SSB > audio that hearing a DV signal does not sound like "real radio". It IS real > radio because it is sent/received via radio waves , but it feels like you > are on Echolink , IRLP, or Skype!. > > > 4. It is exiting to be on air with just the few that are active. If you > expect to hear LOTS of DRM signals, you'll be disappointed. Activity is > less than Hell or MT63! > > 5. WinDRM shows that DV can be done well without expensive outboard hardware > devices (AOR). It works with a fairly low CPU PC. I think we are in the > Betamax-VHS era for amateur radio digital voice, with several incompatible > DV modes. > > > Andy K3UK
Andy, I've had some of the same thoughts. Much of the attraction of Ham radio to a lot of people is the ability to work long distances. CW still lives and PSK31 has been widely accepted because of this. It was quite a thrill when I worked someone in Russia with PSK31 who was using a homebrew rig with 5 watts output. PSK31 has opened Ham radio to a lot of people who can't put up a big antenna or run high power. When I first tried analog SSTV a few months ago I thought about how primitive it was compared to digital communications today. However when I tried HamPal it was very disappointing to find out how difficult it was to receive a picture even with an S9 signal. The picture quality is stunning but the success rate is so low that it will never replace analog SSTV. I had hoped that DV would be able to improve the quality of communication over analog voice in conditions when analog voice was marginal. It seems that if we could trade some of the voice quality for better weak signal performance it would be much more attractive to many hams. With SSTV, weak signal performance could easily be improved by reducing picture resolution and reducing the data rate. That is a little more difficult to do with voice since voice communications must be in real time - we can't just slow the data rate down to fit the channel conditions. I work in cellular communications and know that good voice quality can be maintained with a data rate of 8k bps. It seems reasonable that useable voice quality can be produced with half that data rate. Are there any communications engineers in this group that can give us some idea whether a useable quality digitized voice can be sent over a 2.5 KHz wide HF channel with SNR comparable to or less than what is required for analog voice? Ed Need a Digital mode QSO? Connect to Telnet://cluster.dynalias.org Other areas of interest: The MixW Reflector : http://groups.yahoo.com/group/themixwgroup/ DigiPol: http://groups.yahoo.com/group/Digipol (band plan policy discussion) Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/digitalradio/ <*> Your email settings: Individual Email | Traditional <*> To change settings online go to: http://groups.yahoo.com/group/digitalradio/join (Yahoo! ID required) <*> To change settings via email: mailto:[EMAIL PROTECTED] mailto:[EMAIL PROTECTED] <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
