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[aprssig] DTMF Weather telemetry

Kurt A. Freiberger kurt at badgers-hill.net
Mon Aug 16 01:55:35 UTC 2004


We're all familiar with the 2 of 8 encoding scheme, but there were 
devices that used 3 of 11 - basically they used the 2 of 4 for 0-9, and 
the three other tones to denote the three other rows of a standard 
Hollerith card!  Sorta cute, eh?  I need to find that book again....

73/Kurt

scott at opentrac.org wrote:
> 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)
>>



-- 
Kurt A. Freiberger     Austin, TX	kurt at badgers-hill.net
Amateur Radio Callsign WB5BBW  		AIM Handle: WB5BBW
"Some people are like Slinkys - Generally considered useless, but
  you can't help smiling when you see them falling down the stairs."




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