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[aprssig] ARPS physical layer

Rick Ruhl ricker at cssincorp.com
Wed Sep 15 16:46:58 UTC 2010


Derek,

The APRS data in encapsulated inside a AX.25 unconnected data packet. Down
to the low level, its the HDLC mark and space tones that create the AX.25
packet.

Rick - W4PC


-----Original Message-----
From: aprssig-bounces at tapr.org [mailto:aprssig-bounces at tapr.org] On Behalf
Of ka7o at ka7o.net
Sent: Wednesday, September 15, 2010 11:37 AM
To: Derek Love; TAPR APRS Mailing List
Subject: Re: [aprssig] ARPS physical layer

Check out:

1200 bps FSK full duplex CCITT V.23
Stated in the KPC3+ spec sheet as it's 'modulation'.
http://www.kantronics.com/products/kpc3.html

CCITT is now "ITU" - a google search for ITU V.23 yields:
http://www.itu.int/rec/T-REC-V.23-198811-I/en

That what you're looking for?

73

> I have been scouring the interweb and have so far not found a 
> definitive description of the physical layer / air interface of the 
> APRS system. All the published info seems to revolve around the Link 
> layer (AX-25) which is all well and good, but doesn't let me design a 
> new TNC. Can someone point me in the direction of a suitable source of 
> information, please?
>
> Many thanks.
>
> Derek Love
> G7ORK
>
>
> Registered Office- Oval Park. Hatfield Road. Langford. Maldon. CM9 6WG 
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