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[aprssig] DTMF Weather telemetry

scott at opentrac.org scott at opentrac.org
Sun Aug 15 22:00:44 UTC 2004


That's assuming you leave at least 40 ms delay between characters, which
means you're down to 50 bits/second now.  I think you're better off running
300 baud AFSK.

Scott
N1VG

-----Original Message-----
From: Andrew Rich [mailto:vk4tec at hotmail.com]
Sent: Sunday, August 15, 2004 2:51 PM
To: scott at 3xf.com; aprssig at lists.tapr.org
Cc: ozaprs at marconi.ics.mq.edu.au
Subject: RE: [aprssig] DTMF Weather telemetry


u use the "valid character" pin

You get "3" valid pin -break- "3" valid pin <break> etc etc



----------------------------------------------------------------------
Andrew Rich (VK4TEC)


>From: "Scott Miller" <scott at 3xf.com>
>To: "'Andrew Rich'" <vk4tec at hotmail.com>,"'TAPR APRS Mailing List'"
><aprssig at lists.tapr.org>
>CC: <ozaprs at marconi.ics.mq.edu.au>
>Subject: RE: [aprssig] DTMF Weather telemetry
>Date: Sun, 15 Aug 2004 09:45:26 -0700
>
>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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