D Star emulation.

[Tom Azlin N4ZPT]

Hi Alex,

yes, most of us are not happy with Icom. More importantly we are not 
happy with JARL for not putting in CODEC selection bits in the frame. 
Icom-JARL did pick the most popular and best performing CODEC being used 
for public service/safety radios (but there is a flaw there but that is 
a whole different thread*). The guys working the CODEC2 are thinking 
they can still re-purpose some of the bits. I do not know where you 
live, but here in the Wash DC metro area there are as many non-Icom hot 
spots as there are Icom repeaters. There are also complete non-Icom 
repeaters that are part of the D-STAR networks but all of these are just 
bit regenerators and retransmitters that do not care the content of the 
voice frame data bits. Once alternate CODECs get made the repeaters will 
work fine for those folks. Trick is how to know which type of data. The 
Icom radios will be clueless. Worse Icom Japan simply does not care. 
Icom America is a bit more understanding but is hamstrung.

so is an experimenter area now. I put up the NV4FM D-STAR repeater just 
because I could get NVFMA support. For Fairfax ARES use our FM radios 
and repeaters are our core tools (in addition to various sound card 
modes on HF and above for message handling.).

* The other thread is the FCC push to narrow band public safety/service 
radios to include switching from robust FM to pretty poor digital in the 
face of non-voice noise like sirens, horns, etc. One should have 
realized that horns and sirens were part of emergency service so the FCC 
decision making, or is that the industry lobby wanting to sell new 
radios, is pretty poor in this regards. Our amateur radio FM systems are 
not part of the narrow banding push so we still have robust stuff. And 
we regularly "practice" using no infrastructure.

Off soap box...

73, tom n4zpt



On 5/17/2011 10:25 AM, Alex Fraser wrote:
> Thanks Tom, I just did some Googling to get up to speed. My first impression is
> that Icom missed a chance to sell a lot of radios, perhaps not making as much
> per unit, but once the mode took over a whole bunch of gear.
>
> It will take time to form a second impression.
>
> Tom Azlin N4ZPT wrote:
>>  Hi Alex
>>
>>  On 5/16/2011 11:06 PM, Alex Fraser wrote:
>>>  I've heard they have a USB dongle that does D Star from a computer. It's rather
>>>  pricey. Can the D Star format be done in software emulation? Can the SDR's do D
>>>  Star?
>>
>>  D-STAR has a mixed voice and slow data mode that uses the DVSI AMBE chip for
>>  its CODEC and sends out the mixed voice/data stream at 4800 bps using GMSK
>>  modulation. The USB Dongle, aka DVDongle, includes the AMBE CODEC chip. Only
>>  pricey given low production volume and all the stuff that has to wrap around
>>  the $20 DVSI chip. some hams that do not have a nearby D-STAR repeater use
>>  this to connect into one. Others use this to monitor their repeater when they
>>  travel. Creater of this dongle had to reverse engineer the protocol to get his
>>  device to work properly. But then since he is the author of the major add on
>>  software for the repeaters he had a good head start on that.
>>
>>  You can get software that works with the DVDongle that lets you connect to
>>  D-STAR repeaters or reflectors. You can get 3rd party software that uses the
>>  DVDongle as the voice encode/decode and your computer soundcard to generate
>>  the GMSK signal then pipe that into the 9600 bps port of a VHF or UHF radio.
>>  Say your 706.
>>
>>  So yes, you can do GMSK and the D-STAR framing in software but you can not do
>>  the CODEC in software. There is a team trying to write an unencumbered CODEC
>>  that can be used in an alternate standard but it is not there yet. (
>>  "CODEC2"). But it will never play with the radios that have the DVSI AMBE chip.
>>
>>  The other D-STAR mode is a data only mode that transports tcp/ip at up to 128
>>  kbps using GMSK. Only radio so far is a Icom radio that is on 23cm and runs at
>>  128 kbps. Myself and a bunch others have been using these radios in public
>>  service events for about 5 years now. You could use a USRP and the rig RF
>>  hardware to roll your own.
>>
>>  You can confirm the above with some searches of the web. this has been a
>>  discussion several years long now in the community playing with this.
>>
>>  73, tom n4zpt
>>
>>
>>
>>
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>
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