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D-Star <-> Analog... it's in the D-Star spec...
? ? Posted by: "michaelcarey69" michaelcarey@... michaelcarey69
? ? Date: Fri Oct 15, 2010 12:56 am ((PDT))

Hi Everybody,

I'm not sure if this is common knowledge, I haven't seen it "out there" yet. Apologies if this is old news.

As we all know, the original D-Star specification is written in Japanese. There has been a partial translation to English with a document called shogen.pdf describing the main areas of the D-Star protocol.

I was looking around Satoshi Yasuda's web page last night. Satoshi was one of the people in the original JARL D-Star working group and is also the original developer of the DV Node Adapter that has become very popular worldwide in varying forms.

Anyway, Satoshi has translated some more of the D-Star specification, section 4.2.8 which describes analog to D-star gateway operation.

It's called shogen_4_2_8.pdf. (Attached)

Basically it describes the operation of an "adapter" which includes an AMBE2020 codec chip and I presume from reading the document, a MSK modem. I am also presuming that to use this function, you need a "special" radio that can encode and decode a D-Star like header containing callsign information that is basically the same as the normal D-Star header. This alternative header is transmitted at 1200bps MSK.

My understanding is that one of these radios (which don't exist of course) is a normal FM radio, but with the ability to send and receive the 1200 bps MSK header. When you key up your radio, the header containing URCall, MYCall, RPT1 and RPT2 is transmitted followed by conventional FM audio. The D-Star <-> analog adapter sees this header and then uses the onboard AMBE-2020 to encode the received FM audio and send it though the gateway system.

In reverse, an incoming gateway DV stream (from the internet) would have the AMBE DV audio decoded back to analog. The callsign info would be transmitted in the short MSK header at the start of the transmission, followed by the decoded audio in normal analog FM mode.? The users radio would then decode the MSK header and display callsign information. The advantage the those with "normal" FM radios listening to the repeater would be able to hear the decoded audio.

It would appear that none of the other slow data info would be transmitted, just the voice portion of the DV stream.

I've been thinking all day about this and how it could be implemented with the current D-Star gateway system.? Not having readily available user radios that support this part of the spec would be a stumbling block. The "adapter" part would also need to be developed.

I wonder how much else is hidden away in the D-Star spec that has yet to be discovered?

Interesting indeed!!

Michael.
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