Order Tray | Contact Us | Home | SIG Lists

[aprssig] APRS on all Radios!!!!

Bob Bruninga bruninga at usna.edu
Sun Aug 17 19:17:12 UTC 2008


> Please, can't we just have a fixed-length 
> binary message? 

Yes, that is what I was proposing.  Fixedfields for all APRS data.  Then give that to the stock PSK-31 varicode system so that it was compatible completely with that system.  Being able to montior it or decode it with any off-the-shelf PSK-31 decoder would be a powerful tool.

> Start using varicode (or any Huffman code) 
> and you've got to worry about designing 
> for the worst case data.

No, beacuse the text to varicode to text algoirthms are done.  Built into all PSK-31 applications.  SO that is outside the scope of a PSK-31 approach.  I agree compeltey with fix-length fields for the APRS data (prior to PSK-31 varicoding).

>  Callsigns don't have the sort of letter 
> distribution you see in natural language. 

Yes, but the average bit length for random calls is still only about 6 bits each.  SO ther is no penalty.

> Stop thinking in terms of text strings, 
> and think about data structures.

I like the text strings for trounbleshooting especially if using off-the-shelf PSK-31.  The data structure would be fixed length fields.

But I agree, if there is no interest in using off-the-shelf PSK-31 for all the advanatages of TX, RX, monioring, and troubleshooting, then binary makes sense too.  But not if the only tool for using it is the only decoder itself.  Then there are no options for troubleshooting.

Bob, WB4APR




More information about the aprssig mailing list