[aprssig] APRS Messenger now has APRS over PSK-63

[Stephen H. Smith]

On 2/28/2010 7:32 PM, Lynn W. Deffenbaugh (Mr) wrote:
> Stephen H. Smith wrote:
>> I assume that once APRS Messenger gains the GPS input and capability 
>> to send posits, that this will work to put APRS posits on the map in 
>> any (or all) of these programs.    To make the most of the slow PSK 
>> transmission rate, I would strongly suggest that APRS Messenger use 
>> the highly-compressed MIc-E transmission format since it is about 
>> ONE-THIRD the length of a plain-text APRS posit. The downside is that 
>> it is not human-readable, although ALL APRS mapping applications can 
>> decode it.
>
> My only comment on the Mic-E format for APRS Messenger is that part of 
> the author's intent was to allow users to visually decode incompletely 
> received or partially garbled transmissions.  Yes, Mic-E will save 
> transmission time, but will take you back to the entire packet needing 
> to be received before any sense can be made of the position.
>
> Lynn (D) - KJ4ERJ - Just my $0.02
>

In the real world of noise, trash and constantly shifting propagation on 
HF, Mic-E makes a major difference in the success rate of posits on 
HF.     In experiments I did with a TinyTrak III on an HF mobile (FT-100 
into a ATAS-100 screwdriver) about two years ago, nearly twice as many 
posits were successfully received using Mic-E compared to the standard 
APRS format for positions.

While you may be able to guess at the content of a garbled text message, 
I don't know how you would be able to guess at the missing digits of a 
mangled position report.  (Unless they happen to be the least 
significant decimal minutes values -- then the rest of the digits might 
still be useful.)


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