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[aprssig] Looking for 9600 baud equipment

Bob Bruninga bruninga at usna.edu
Sun Sep 28 19:23:36 UTC 2008


> My first batch of data radios is due in soon...
> so I figure it's about time to start working on 
> 9600 baud support for my next TNC project...
>
> I'm hoping to find at least a few different TNCs 
> for compatibility testing.  A KPC-9612 and a...
> G3RUH modem would be great for starters.

Another good goal might be to test for good compatibiliy with the 10's of thousands of APRS users that already have identical 9600 baud TNC's built into their APRS radios.

> ... which ones use a root-raised cosine matched 
> filter, ... which ones are actually G3RUH-compatible.

I don't know, but these thousands were all built on the same professional assembly line to tight standards, so one would assume that they are pretty consistent in their performance.  Thus reducing the risk in trying to be compatible with a very large user base (even if they are not currently using them at 9600 baud).  They can with one menu button.

I agree, that there is just SO MUCH we can do with packet radio, and so 9600 baud is a good path.  But we have got to start delivering meaningful useful information in the applications to the end users, or it is the sound of one hand clapping.

Using existing repeaters, existing radios, existing software, existing everything, each existing voice repeater can deliver over 1 Mbyte per 30 minute commute to every mobile on the road. And with dozens of repeaters in metro areas, we can deliver hundreds of megabytes overnight or during the day and all SEAMLESSLY with voice.

I cannot find a copy my 1990's paper but it is simple.
The INPUT channel of all voice repeaters when not in use, can stream-outward these bulk data rates in 1 second bursts of 9600 baud traffic.  Then listen for 1 second for any conventional FM voice user who wants to use the repeater.

THus the existing FM voice user is never more than 1 second away from seizing the channel and the repeater for normal voice operation.  But as soon as the repater drops, it can go back to streaming ham radio content from that same repeater on the INPUT channel.  MObiles add a 9600 baud receiver on the INPUT frequency and capture this streaming data all day long anytime, anywhere over the coverage area of that repeater.

And nobody hears it.  Because no one is listening on the input.  ONLY the repeater INPUT receiver is "listening" so it can very easily share its high location with something Transmitting data in one second bursts from the same antenna.

Back when I wrote it, we envisioned something like a HRW, Ham Radio Web, that was continuously streaming and updating background web content to everyone's PC, so that when they "browsed" any of the popular ham radio content, their PC aleady had a fresh copy.

Yes, there are some coordination issues, but we have a HUGE amount of unused spectrum.  Of 100 voice repeaters in the Baltimore/Washington area, maybe 10 are even at use during prime time.  The other 90 can be streaming (in one sec bursts) almost 3 MB per minute.

So much bandwidth... so few applications...

Bob, WB4APR




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