Re: LF: Re: RE: Full ID

[Andy Talbot <andy.g4jnt@gmail.com>]

Joe Taylor has come up with the tightest source coding of amateur callsigns as built into the WSPR and JT65  protocols.   

By examining the make up of callsigns from letters numbers and spaces, with even those restricted in where they lie in the callsign, he compresses all possible ones - bar a few special event types - into 28 bits.   Full coding details are in http://www.g4jnt.com/Coding/WSPR_Coding_Process.pdf 

 

What we need now, for LF, is a way to turn the 28 bits of data into a frequency shift + on/off keyed scheme for reading directly off screen.  Something better can probably be done than Morse / DFCW,  although to read without the use of computer decoding will require a new operator skill / language to be learned.   (Somehting for the already perfect CW OPs to get their teeth into  perhaps :-)

It ought to be poossible to code something up that is appreciably shorter than the full callsign, yet conveys that unambiguously.  But, note that as the callsign has now had all its redundancy removed, ANY errors in decoding will generate an equally valid-looking but erroneous callsign.    That's the penalty of good source coding - we see it occasionally on WSPR reports when noise/QRM manages to pass the error detection tests.

 

Andy

www.g4jnt.com