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[aprssig] 9600 APRS

Wayne Sanderson whsander at gmail.com
Wed Mar 2 01:55:50 UTC 2011


I regularly used a wireless PDA years ago that ran on a dedicated
packet data network. It used an interesting transmit/receive scheme.
The upload side of the device sent data up to the network at 4800, but
the downstream packets from the network came down at 19200. The idea
was that the end user in everyday use generally sent very little up
compared with receiving quite a bit down, which was how they got away
with the speed difference. It made sense too, considering that the end
user only sees the speed of the data he receives, and doesn't care
what speed the stuff he sends goes out, as long as it goes.

I wonder whether a dedicated offset freq for digi access set to a
lower speed with network reception on the mobiles set at the higher
speed would ever be possible. I imagine one would either need 2 TNCs,
each set to a different speed, or a TNC set to 9600 or whatever speed
one wanted to run on the main channel and a straight one way transmit
only modem on the uplink channel set at a lower speed.

I wonder whether a skillfully written software modem might be able to
handle all speeds on the same channel and be able to send/receive them
all.

>>>I guess 4800 would be a little improvement, but I'm really thinking of two goals here -- 1. A solution to channel congestion. 2. An end to desensing a 2-meter voice radio. Two meters is our most popular voice band. It would be nice to move voice to 70 cm, but that's a long ways off for those of us "way out in the sticks". Vy 7 3 Earl KD5XB

>>> ------Original Message------ From: Scott Miller To: My Gmail Earl Needham To: TAPR APRS Mailing List Subject: Re: [aprssig] 9600 APRS Sent: Feb 28, 2011 16:34 I'd rather see something more robust, like 4800 baud with lots of FEC and a better channel access control. Scott N1VG



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