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[OZAPRS] RE: [aprssig] DTMF Weather telemetry

Robert Bruninga bruninga at usna.edu
Fri Aug 20 14:40:07 UTC 2004


I think the TTone spec requires dead time between
each character even if it is different.  That is part
of the high reliability detection scheme... I think... Bob

>>> scott at 3xf.com 8/15/04 12:45:26 PM >>>
Sure, but your data rate is somewhat limited.  I think the minimum
symbol
time is 40 ms, so that's 25 characters per second, 4 bits per
character, so
100 bits per second.  If you're lucky.  You still need to worry about
sync..
say you've got a long run of '3's - the tone isn't going to change. 
You
need a clock at the receiver synced to the transmitter's clock to know
where
each character starts.

Scott
N1VG

-----Original Message-----
From: aprssig-bounces at lists.tapr.org 
[mailto:aprssig-bounces at lists.tapr.org]On Behalf Of Andrew Rich
Sent: Saturday, August 14, 2004 11:56 PM
To: TAPR APRS Special Interest Group
Cc: ozaprs at marconi.ics.mq.edu.au 
Subject: [aprssig] DTMF Weather telemetry


Has anyone ever used DTMF to send telemetry ?

Example

A278B015C027

Wind 278 deg Speed 015 Temp 027

Or even APRS ?

27*34*45A = 27.34.45B (assuming * = . and A = North and B = South)
153*06*21C = 153.06.21E ( assuming * = . and C = West and D = East)

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