<html><body><span style="font-family:Verdana; color:#000000; font-size:10pt;"><div>Hi Kevin -</div><div><br></div><div>I just got on d-Star over the holidays. I am using the Icom ID-31A. Last week I just picked up the Moen gmsk modem board to create a hotspot. You may want to check out this website <a href="http://www.k6jm.com/hs-setup.htm">http://www.k6jm.com/hs-setup.htm</a><br></div><div>People are using the RaspberryPi for the pc. I am using an old dual band Icom mobile that has 9600 bps din connections. Using the test program, I can transmit from the ht into the gmsk modem but the modem is supposed to play a canned message back to the ht, which is the part that I am having trouble with. I hope to have enough time this weekend to get this bug out. Long story short - I have been a ham for 42 years and D-Star is fun!</div><div><br></div><div>73 - Don KS9F - Durham</div><div><br></div>
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-------- Original Message --------<br>
Subject: [Linux-ham] portable digital voice<br>
From: Kevin Otte <<a href="mailto:nivex@nivex.net">nivex@nivex.net</a>><br>
Date: Wed, January 16, 2013 10:29 pm<br>
To: <a href="mailto:linux-ham@trilug.org">linux-ham@trilug.org</a><br>
<br>
; Rationale<br>
<br>
At RARSFest a few years ago, there was a great buzz around D-STAR. <br>
Unfortunately, the discussions about the non-Free codec were a bit animated.<br>
<br>
Now that we have some options, I'd like to try to have a functional demo <br>
for RARSFest this year. And by functional I mean walking around using <br>
it, not just on a booth table.<br>
<br>
What follows are my ramblings on how we might go about this. It is in <br>
some part an attempt at organizing my own thoughts, but the closer to <br>
the RF hardware I get, the weaker my skills are. I'd love some insight <br>
from others. As such, we'll start there and work our way up the stack.<br>
<br>
; Modems<br>
<br>
At the modem level we have a few options: FDMDV, G3RUH (the 9600 baud <br>
packet standard), and GMSK.<br>
<br>
The FDMDV modem is part of the Codec2 development and delivers a 1400 <br>
bit/s stream in about 1.1KHz of bandwidth. It is primarily designed for <br>
HF, but could easily be routed through an HT audio connection. Details <br>
here: <a href="http://www.rowetel.com/blog/?page_id=2458">http://www.rowetel.com/blog/?page_id=2458</a><br>
<br>
Using 9600 baud TNCs would make for a nice reuse of older equipment, <br>
much as APRS does. Some radios such as the TH-D7 have these modems <br>
built-in already. I'm not sure how easy it is to lay hands on more of <br>
such equipment though. I also seem to recall that getting seperate <br>
radios and TNCs tuned up was a bit of a challenge, but that was also ~20 <br>
years ago. (Where does the time go?)<br>
<br>
In newer territory, using GMSK would in theory be a better use of the <br>
spectrum. I don't know as much about how to make this work. There is a <br>
Belgian ham ON1ARF doing some early work on this front: <br>
<a href="http://villazeebries.krbonne.net/hamstuff/?cat=5">http://villazeebries.krbonne.net/hamstuff/?cat=5</a><br>
<br>
; Codecs<br>
<br>
The seemingly obvious choice here is Codec2. It was designed for this <br>
very purpose and has already earned the 2012 ARRL Technical Innovation <br>
Award. I even had the pleasure of meeting David at the Dayton Hamvention <br>
last year.<br>
<br>
Another option would be the recently IETF standardized Opus codec. The <br>
drawback here is that its lowest bitrate is 6Kbit/s. Though, if using <br>
something that is 9600 capable, an 8 Kbit/s voice stream could be used <br>
for great audio quality and room to spare.<br>
<br>
; Systems<br>
<br>
For initial mockup and testing, full PCs will make life easy. Once you <br>
get into the realm of needing to carry it around, that's where it gets <br>
interesting.<br>
<br>
With the recent buzz around the Raspberry Pi, this seems like a leading <br>
possibility. ON1ARF's work as well as some other discussion I've read <br>
seem to indicate that the audio capabilities of the Pi are less than <br>
stellar.<br>
<br>
There are all manner of embedded systems out there these days. So many, <br>
in fact, that I won't even pretend to try and keep track of them all. <br>
Suggestions welcome.<br>
<br>
; Conclusion<br>
<br>
So there you have it, an attempt at a braindump of my epic idea... at <br>
least I hope it sounds as epic in this message as it does in my head :)<br>
<br>
It's a lot of work, and it may not even come to fruition, but hopefully <br>
getting this out of my head and into the air will let my brain spin down <br>
a little.<br>
<br>
73 de Kevin, N8VNR<br>
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