Monday, January 10, 2011

Automatic Voice Relay System

One of the reasons why I have not been an enthusiast of the D-Star system is that it creates a separate class of activity incompatible with existing voice modes just for the dubious benefit (from an amateur point of view) of using digital voice instead of analogue. Using EchoLink, IRLP and APRS we already have a global network that allows one ham to contact another anywhere in the world using ham radio, one that does not require anyone to purchase expensive new equipment from Icom or anyone else. What we have not done is put it together in a way that makes it work seamlessly as a coherent network.

Automatic Voice Relay System (AVRS) is an idea by Bob Bruninga, WB4APR, the inventor of APRS, first published in 2000, to create a system that allows users of EchoLink, IRLP and even D-Star to inter-communicate. APRS provides the location and identification information for the analogue FM EchoLink and IRLP users, something that is already built in to the D-Star system. As is often the case, those who have the great ideas don't always have the skills needed to bring them to fruition, so AVRS remained little more than an idea for ten years.

Now, apparently, a developer has been found who is able and willing to write the software that will enable AVRS version 2 to come into being. You can read more about AVRS here. For seamless one-button operation you will need one of the new generation of APRS-capable radios (Kenwood TM-D710, TH-D72 or Yaesu FTM-350) that are able to QSY to a frequency contained in an APRS packet. Some will argue that if you are going to buy one of those, why not buy a D-Star radio instead? But AVRS capability, being based on APRS, can easily and inexpensively be added to any analogue FM radio. AVRS will not leave analogue FM users out in the cold because their local repeater converted to D-Star, as has happened in some parts of Britain.

One of the interesting aspects of AVRS version 2 is the development of A-Star repeaters. These are analogue FM repeaters with a D-Star gateway that use the D-Star network to link them together. Callsign and location (if known) information is transmitted as a 0.3sec APRS packet burst at the end of each over. A-Star users will appear to D-Star users just like other D-Star users and can easily intercommunicate. A-Star users can initiate a contact with another A-Star or D-Star user just by sending an APRS message starting with A*. A-Star users don't even need to be monitoring a repeater in order to be contactable: they will receive the message as an ordinary APRS message and can QSY to the repeater (with one button press if using one of the radios mentioned above) using the information contained in it.

AVRS looks like a great idea with the potential to bring digital and analogue voice users together. It might even erode some of the analogue vs D-Star conflict.


Tim said...

I agree, Julian - this looks very interesting! Will be fascinated to see it evolve, but if it develops as it appears it could, it could be a key piece in the jigsaw puzzle.

Happy New Year (somewhat belatedly!)


Fenris said...

I have to say that my preferred approach would be to only link from analogue repeaters to D-Star systems that are running 100% freely implementable configurations (so not the AMBE codecs thank you).

I appreciate that this may be holding back progress, but amateur radio is not about using proprietary technology.

Unknown said...


All dstar rigs have this ability. They are also comparable in price to the Kenwood TM-D710 or Yaesu FTM-350. The rigs operate Digital APRS and also have a messaging option. So why "cobble" something together, when you can purchase a radio with the above availability built in?

Andrew M1DNS.

Unknown said...

Because there are still far more users on analogue than digital, because many people will never buy D-Star if it means having to buy Icom and/or use a proprietary codec, because it is about enabling analogue and digital users to talk to one another instead of forcing people to choose one or another.

Unknown said...

Yes there are more analogue users than digital, but there were more AM users than SSB users back in the early 70S / late 60's. To say a yaesu or kenwood radio is better than an icom really is clutching at straws. You might want to check with the reflector owners, as a lot of them will not permit analogue audio on their systems, I have the ability too x-connect both systems, and did this as an experiment, i only did it once. (the idents + pops and crackles of my local ana. rptr was not appreciated on the digital reflectors) there are only a couple of reflectors permitting analogue audio and that is the freestar reflector XRF005 and xrf044, and these only permit audio connections via IRLP. you will not be able to connect to any of the major reflectors (ie US or US Trust)

Andrew M1DNS.

Ps it might appear that i am anti avrs this is not the case.. i like all forms of radio, and run many systems here aprs/ d-star/ echolink/ skype-link / drm-rdft etc etc. with regular data and voice nets on 2m / 70cms (ana. and digital). and I'm also looking for the next idea of what we can do within amateur radio to make it better.... or what if this could talk to that etc. so i wish John ABoOO best wishes with the project, but it might be harder than first envisaged by Bob Bruninga.

Unknown said...

Thanks for your perspective on the issue, Andrew. It does seem rather sad to me though if people are not wanted on a reflector because of their analogue audio (I'm not sure about pops and crackles though, what were they doing, playing 78's?) It sounds to me like a group of people saying "our system is better, either join or keep out." Sadly that kind of attitude is not exactly unknown in this hobby, why should I be surprised?

I'm not saying that one system is better than another, I'm arguing for a system that helps the two systems communicate so people don't feel excluded or forced into going digital just because others have. Historically, ham radios have had a life of 30 years or so providing new hams with a cheap way into the hobby. If everyone went digital the cost of entry would suddenly become several hundred quid. Creating D-Star may have been good for Icom shareholders but I don't think it has done anything for the hobby as a whole dividing it into two camps, the digital haves and the have nots.

Anonymous said...

I have been into APRS SINCE December 2004 . I got APRS started in this area of NC . I think it is is enjoyable , however D-STAR is more enjoyable . Using a MOENCOMM STAR BOARD or other equal device you have your on D-STAR hotspot . I use a motorola 900 baud gm300 mobile with the board . Total cost around 150 us dollars . The D-STAR radio was purchased . I am an avid cw op , however D-STAR has allowed me to make the world smaller . I have friends in Britain and of course the US I speak with daily . Give it a try you just might like it . CHUCK N4UED

Anonymous said...

I got aprs started here in the North EAST area of NC back in December 2004 . It has caught on in force . I am now experimenting with D-STAR . This is a very interesting technology . I have met many friends in the UK . I find that DPRS has little use compared to APRS . The good thing about D-STAR is you talk in voice with people . I have used APRS in public service and it worked flawless . D-STAR is another way of meeting hams around the world when you are antenna restricted . CHUCK PRIDGEN N4UED