[Xastir] More detail on 300 baud transceiver...

[Bob Donnell]

Hi Chris, and all,

One of the problems you face right off the bat, with using a standard PC
RS-232 serial port, is that it can't directly produce 8-bit synchronous data
- it will add in start and stop bits.  That's one of the reasons KISS was
developed.  

Another device, the YAM modem, required using a serial port baud rate that
was double that of the on-air rate, to allow it to deal with the synchronous
HDLC data format specified for AX.25.  Of course, you could use ASCII data,
but then you lose the built-in ability to detect errors in the data frame.

So if you do decide to use a standard PC serial port directly, what you
create on the air will only be able to be copied by others using the same
scheme.

Hope that helps better explain the situation,

Oh - and you can thank Curt for pulling me into the discussion!

73, Bob, KD7NM

-----Original Message-----
From: xastir-bounces at xastir.org [mailto:xastir-bounces at xastir.org] On Behalf
Of Chris Moulding
Sent: Tuesday, June 24, 2008 12:05 PM
To: xastir at xastir.org
Subject: [Xastir] More detail on 300 baud transceiver...

Thanks to Dave G0CER and Curt WE7U for your replies.

Dave, re using packet radio on 160m. I'll check the regulations. Local
amateurs did a trial run around the West Pennine hills last year to prove
the idea. If not we could also use 30m. Tests locally show reliable ground
wave coverage out to 13 miles using mobile equipment on 10 MHz..

Curt, I'll give some more info on the transceiver project. It uses direct
FSK modulation of the transmit carrier and phase lock loop detection of the
received FSK signal. There is no audio input or output so the use of
computer sound cards is out. My idea was to send and receive at 300 baud
directly from the serial port. The test with the OT1+ uses the direct FSK
output firmware to directly drive the transmit FSK modulator. It would be
ideal if we could use Xastir for it's messaging, igating and other
properties.

73,

Chris, G4HYG



      
_______________________________________________
Xastir mailing list
Xastir at xastir.org
http://lists.xastir.org/cgi-bin/mailman/listinfo/xastir