Wednesday, December 08, 2010

Yet Another Digital Mode

Windows PC users now have the option to try yet another weak signal digital mode. Called V4, it is described as "a robust, easy to use, keyboard sound card mode that would fit into the narrow digital segments of our HF bands." The mode is 200Hz wide and capable of sending text at 40 - 60 words per minute.


Do we need yet another keyboard digital mode? Although PSK31 is very popular and very narrow, performance deteriorates under conditions of multipath reception (such as in NVIS propagation) or when the ionosphere is disturbed (polar paths during periods of auroral activity) while RTTY, though also popular, is archaic, inefficient and successful only by brute force methods (a big amplifier and a beam.) More robust FSK modes such as MFSK, Olivia, Thor and DominoEX perform better but are much wider which can be a barrier to use. V4 uses the same robust modulation scheme as WINMOR but has been optimized for use as a keyboard chat mode. A detailed protocol description can be found here and the software can be obtained after joining the V4 Protocol Yahoo Group.

I have only just been admitted to the group so I have some reading to catch up on and it will be a few days before I can find the time to try V4 for myself. However I am quite interested in this mode which seems to have been developed by licensed hams keeping in mind the need for responsible band use (so no 2.2kHz wide signals!) and with all the details being published and open. The software modem has been implemented as a standalone TNC that can be interfaced with other applications such as my own program KComm which is also interesting to me. So I think you can expect to hear more about the V4 Protocol in this blog in the weeks to come.

7 comments:

Paul - PC4T said...

Hello Julian, sounds interesting. I am always in for new experiments. I will read the information about it. 73 Paul

PE4BAS, Bas said...

Sound indeed interesting Julian. I guess the implementation of the TNC would be interesting to use for applications like a mailbox or so? Or a kind of APRS function. Or something like PSKMail. Hope to read from it soon. 73, Bas

Julian said...

No. The WINMOR protocol is intended for data transmissions like WinMail and APRS. This is an offspring of that, designed specifically as a keyboard chat mode. By the look of things you may find it between the top of PSK31 activity and the start of JT65A, though it is not 'channelized' and can be used anywhere a 200Hz wide digital mode can legally be used.

Steve Silverman said...

V4 could become the most practical and popular digital mode since PSK31 due to its robustness and reasonable bandwidth along with speedy chat interactions.

Keep us posted, Julian.

Steve KB3SII

PE4BAS, Bas said...

Hi Julian, it looks promising. But it is still not clear to me what the TNC is for then. Is V4 that much better as PSK31? What you show us till now is also possible with PSK31 or Olivia or any other mode. Anyway, I'll await more postings on your blog. What I understand is that V4 is better as PSK31 but less sensitive as JT65A. Now JT65A does need time to decode a message and V4 probabely decodes realtime, true?
73, Bas

Julian said...

Yes it should be much more robust than PSK31. Probably not better than Olivia but it is much narrower (200Hz) for the same speed. Not as good as JT65A but it is a keyboard QSO mode you are not limited to sending fixed format information (or 13 characters) and it is faster and decodes in real time, no clock syncing necessary. You could say that it aims to achieve what ROS mode does, but without the excessive use of bandwidth.

The TNC is essentially the sound card modem. You get two programs, one a fairly primitive chat application and the TNC with waterfall display and status indicators. The two talk to each other using TCP/IP. It would be possible for HRD, Fldigi and other programs to talk to the TNC in the same way so people could use their own familiar interface. That's what I hope to do with KComm if the mode proves popular enough to be worth persevering with.

At the moment we are only using the FEC (Forward Error Correction) mode. But there will also be an ARQ (Automatic Repeat reQuest) mode which will ask for repeats of blocks that were not received correctly so it will keep on going until you get perfect copy just like Pactor does. So I think V4 really has the potential to exceed what is possible with other sound card modes. But it is early days and the value of getting involved now is to help with testing and getting the bugs out of the software.

PE4BAS, Bas said...

Hello Julian, thanks for the explanation. It's clear to me now. I think that is a real advantage over ROS and JT65A(HF). It keeps my interest....73, Bas