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[aprssig] What sets the max packet length for APRS

Steve Daniels steve at daniels270.eclipse.co.uk
Sat Nov 10 17:57:12 UTC 2012


There is a handheld radio that will only display 45 character, anything over
that is lost, it's a Yaesu but I forget the model

 

Steve Daniels

G6UIM

Torbay Freecycle Moderator
http://http://uk.groups.yahoo.com/group/torbay_freecycle
<http://http:/uk.groups.yahoo.com/group/torbay_freecycle> 

APRSISCE/32 Beta tester and WIKI editor http://aprsisce.wikidot.com

 

  _____  

From: aprssig-bounces at tapr.org [mailto:aprssig-bounces at tapr.org] On Behalf
Of Lynn W. Deffenbaugh (Mr)
Sent: 10 November 2012 16:28
To: TAPR APRS Mailing List
Subject: Re: [aprssig] What sets the max packet length for APRS

 

As I understand the history, there are some radios that won't even display
the 67 characters.  There are/were TNC limits on how long UI packets could
be overall.  Some TNCs can do longer, and the APRS-IS carries a much longer
limit.  But the specification tells you what should work.  Exceeding those
limits may result in unexpected behavior, but as you've observed, there are
lots of packets out there that seem quite long.

BTW, after the colon is the payload.  That particular packet has a
timestamp, position information, weather, and a final comment.

Lynn (D) - KJ4ERJ - Author of APRSISCE for Windows Mobile and Win32

On 11/10/2012 11:21 AM, Bryan Hoyer wrote:

APRS1.01 states 67 characters for a message and up to 43 for a comment, yet
I see packets twice that long on APRS.FI. This ones 109 after the : 

 

 <http://aprs.fi/?c=raw&limit=&call=KA8OAD-1> KA8OAD-1>APU25N,
<http://aprs.fi/?c=raw&limit=&call=K8YSE-1> K8YSE-1,WIDE1,
<http://aprs.fi/?c=raw&limit=&call=K8UI-1> K8UI-1,WIDE2*,qAR,
<http://aprs.fi/?c=raw&limit=&call=K8LI-1>
K8LI-1:@101613z4108.09N/08136.25W_190/004g005t057r000p020P020b10220h51FWX_ht
tp://pages.sssnet.com/kend Fairlawn,OH

 

AX.25 says 256 bytes for the UI payload

 

A Tweet is 140 characters

 

An SMS is 160 characters

 

Is it just the display limit of some radios?

 

Just exploring the capabilities and limitations of APRS

 

Thanks!

Bryan Hoyer - K7UDR

 






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