[aprssig] D710 GPS Port

Scott Miller scott at opentrac.org
Tue Aug 14 12:46:51 CDT 2007

See my last post about the state of the spec.  I think it might be 
enough (if you can read the bits of the PDF that seem to be missing a 
Japanese font) to build a working system IF you had a working example to 
start from and analyze.

The layer 1 stuff is REALLY sparse.  It lists a modulation method of 
GMSK, QPSK, or 4FSK, with a maximum data rate of 128 Kbps.  That's it - 
no more details on modulation, speed negotiation, or anything.

Plus, it uses the AMBE codec.  From the Wikipedia article:


AMBE is controversial in that the licensing terms are very restrictive. 
While a licensing fee is due for most codecs, DVSI does not disclose 
software licensing terms. Anecdotal evidence suggests a minimum fee from 
$100,000 to $1 Million. PC implementations are not allowed. For the 
purposes of comparison, MP3's licensing starts at $15,000. For 
small-scale use and prototyping, the only option is to purchase a 
dedicated hardware IC from DVSI.

Now is that in any way in the spirit of ham radio?  That the only way to 
generate a compliant signal is to buy a dedicated IC, that comes with a 
huge EULA and costs $33 in lots of 5?

Using a restricted, proprietary codec really irks me - ham radio's 
always been about experimentation and homebrewing, about knowing how 
your equipment works and being able to work to improve it.  And here 
Icom selects as a critical, central component a device that we're not 
ALLOWED to try to understand, to duplicate, or to reverse-engineer.

I know a lot of people have already shelled out a significant amount of 
money for D-Star equipment, but to be honest I really hope that it never 
catches on.  Every little proprietary black box we come to rely on is 
another nail in the coffin of amateur radio.


William McKeehan wrote:
> As for the proprietary stuff, I thought the same thing until I read this 
> months QST. They have a overview of D-star that says it's open to other 
> manufactures. I was wondering if anyone is building D-star hardware like 
> a HAMhud without the need for an Icom radio.

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