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[aprssig] ARPS physical layer

Curt, WE7U curt.we7u at gmail.com
Thu Sep 16 12:13:15 UTC 2010


On Thu, 16 Sep 2010, Derek Love wrote:

> What's the preamble sequence and length?
> What's the sync sequence and length?

I've seen TNC's send multiple flag characters during the TXD time
before the first packet, others send 0x00 bytes.  0x00 bytes are
better as they let the DPLL at the receiver sync up to the clock
faster.

Also be aware that there are TNC's out there which are broken in
various ways.  Some cannot handle long packets, others can't handle
back-to-back packets.  My take on this is that these TNC's should be
ignored/deprecated as they don't follow the spec.  Follow the spec
yourself and call it good.

-- 
Curt, WE7U.                         <http://www.eskimo.com/~archer>
    APRS:  Where it's at!                    <http://www.xastir.org>
   Lotto:  A tax on people who are bad at math. - unknown
Windows:  Microsoft's tax on computer illiterates. - WE7U.
The world DOES revolve around me:  I picked the coordinate system!"



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