Saturday, September 20, 2008

D*STAR, D*CHAT, and D-RATS

The next topic from this month's QST deals with one of my pet peeves in amateur radio today: D*STAR. D*STAR (Digital Smart Technologies for Amateur Radio) is a digital voice "standard" being developed mainly by Icom, in conjunction with the Japanese Amateur Radio League, with funding from the Japanese government. My reason for disliking D*STAR is that D*STAR presently uses the proprietary AMBE encoding, which is locked up tight under restrictive patents held by DVSI. The lack of openness of the AMBE encoding means that there can be no homebrew solutions that interoperate with Icom's commercial products. Most of the rest of the D*STAR standard is open, although I've seen comments that suggest that the 10 GHz data protocol is also proprietary.

The nice thing about D*CHAT and D-RATS is that both of them operate in the data portion of the D*STAR standard, and therefore don't involve the patent issues that D*STAR voice runs into. D*CHAT is a basic SMS application for use with D*STAR that has been around for a while now; D-RATS is an expansion on D*CHAT that provides file transfer capabilities, GPS integration, and some simple form processing (which would appear to be really useful in a disaster management context). I'd be interested in knowing if there's an implementation that can be used with any radio, in conjunction with a software implementation of D*STAR. Since neither D*CHAT nor D-RATS use voice, they don't need the AMBE support, and the rest of the standard can theoretically be implemented in software and run out into any1 radio using a RigBlaster or similar technology. In my opinion, this would be a good thing, as it would help to break Icom's lock on the D*STAR standard; a non-Icom implementation of D*STAR (less AMBE) combined with an alternative voice codec, would go a long way to giving amateurs a real option for digital voice that preserves the right to experiment and to innovate.

1As Greg points out in the comments, by "any" I mean "any SSB radio with a wide enough passband". Admittedly, that rules out most of the VHF and UHF radios on the market, since the vast majority of VHF and up radios for hams are FM only.