[aprssig] 433 MHz operation

Scott Miller scott at opentrac.org
Wed Feb 15 12:40:23 CST 2012

Yes, when I said the OTUSB uses them transparently, I mean that they 
behave exactly like they would for normal APRS, including KISS mode. 
Buffering is still limited, but that will be changing - the OTUSB and T3 
both have RAM available for a larger outgoing packet buffer, but the 
code needs some major changes and a lot of testing to make sure it can 
handle transmitting continuously while it still does everything else 

The current prototype boards only have a USB mini-B connector and a 
6-pin wafer connector for a GPS receiver, and no regular RS-232 serial 
ports.  The PA needs a 12v supply, so they still need an external power 
source aside from USB.


On 2/15/2012 10:29 AM, Bradley Haney wrote:
> will we be able to possbile use these in a KISS mode?
> On Wed, Feb 15, 2012 at 12:12 PM, Scott Miller <scott at opentrac.org
> <mailto:scott at opentrac.org>> wrote:
>     Hi all,
>     I've been playing with some half-watt 70 cm data transceivers
>     lately. I'm currently testing at 434 MHz, and with the standard
>     crystal they should cover about 430 to 439 MHz.  I'm not really
>     familiar with the 70 cm band plan and figured I'd check here and see
>     if people consider that a reasonable part of the band to be working in.
>     I've got another small batch of them coming soon and might start
>     selling a board based around it for people who want to experiment.
>       Right now I'm using an OpenTracker USB variant.  It's currently
>     running at 4800 baud with some basic FEC - a (7,4) Hamming code with
>     interleaving, not fancy but easy to implement.  The transceivers
>     will go up to 115200 bps.  When I have time, I'll see if they can be
>     made to inter-operate with G3RUH TNCs, but for now I'm going to
>     assume that won't work.
>     The really attractive part is that they're cheap - retail price
>     should be not more than 1/3 what we're selling the half-watt
>     transmit-only 2-meter modules from SRB for, and they're about the
>     same size.
>     There are still some bugs to be worked out, but the OpenTracker USB
>     (and by extension the Tracker3) will presently work transparently
>     with these radios, doing APRS at 4800 baud with error correction.
>       I'll be working some more on them to improve mesh routing and
>     channel access control to try to make them more suitable than
>     vanilla APRS for short range, high rate tracking applications.
>     Scott
>     N1VG
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