Return to KLUBNL.PL main page

rsgb_lf_group
[Top] [All Lists]
<prev [Date] next>
[Advanced]
 <prev [Thread] next>

Re: LF: 500kHz 1mW WSPR beaconing

from [Andy Talbot] [Permanent Link][Original]
To: [email protected]
Subject: Re: LF: 500kHz 1mW WSPR beaconing
From: Andy Talbot <[email protected]>
Date: Sun, 25 Oct 2009 20:42:13 +0000
Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=googlemail.com; s=gamma; h=domainkey-signature:mime-version:received:in-reply-to:references :date:message-id:subject:from:to:content-type; bh=lkEKG/n6z5XgDe648LNZKdfk6tge6tQkwwUeJXv+IRM=; b=lPH4BU/ITGC3D6IC3EiJ3tg8CRYQuE0LgF1a2pOI2DHXQz6gcRlTtyGy4OpV7HAgvi 2szWRJ9Rv9TZvPNIg1g1YZ5+VYYT/W5C+z9tsIvFj8RIED01lqsMcTz6yVE965oAkg0q uf28G6rGpsa6w/kC6iBt5boXwabUU9rJVfTwo=
Domainkey-signature: a=rsa-sha1; c=nofws; d=googlemail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; b=RzdOn0sunSB16MunqM/txRMgHzauM79ogYsGdgPGBRMo/fAGpFQ2pTNjzBqfVKwhso ltwxSfVFNWQ/yavrG+SXoGWPv4FamN3nMHkdMDV8EHtvPEV1q0PnBLjX2hG9CKIZPnyK dcP8KM89y2EoLe7K1gz7TQFKhZHdVD0X0r5Zg=
Domainkey-status: good (testing)
In-reply-to: <14E9228C113E44A6A66C5DEF8A144F28@AGB>
References: <[email protected]> <14E9228C113E44A6A66C5DEF8A144F28@AGB>
Reply-to: [email protected]
Sender: [email protected]
---
There is no 'chance' involved.  The strong source coding employed in all the WSJT modes to get the number of bits to be encoded down to an absolute minimum, before proper error correction is added, removes all wasted redundancy in the original callsign format.   This has the result that most truly random bit patterns will therefore generate a valid looking callsign.  Its an artefact of efficient coding.
 
That this only happens occasionally is due to the strong properly constructed error correction that is subsequently added.  
 
 BUT    As the callsign is not encoded in the most efficient way it could possibly be (which would be a codebook of all the radio-ams in the world  = 1 million perhaps with a 20 bit reference number) we identify an invalid callsign by experience, and by correlating with known propagation / locator facts.  
 
Information theory is a wonderful study - and being able to be put into practice more easily with cheap processing power than it ever was before.   I'll be covering this, amongst other aspects of weak signalling, at the Martlesham Microwave Roundtable.  http://mmrt.homedns.org/start.html   (talk entitled 6dB better than CW.)

Andy
www.g4jnt.com

this email has been scanned for political correctness by the nanny state


2009/10/24 Graham <[email protected]>
Roger
 
This happened ..
 
G ,,
 
Timestamp Call MHz SNR Drift Grid Pwr Reporter RGrid km az
 2009-10-24 16:58   G3XBM   0.503917   -28   0   JO02dg   0.001   G0NBD   IO83   261   302 

Sent: Saturday, October 24, 2009 4:55 PM
Subject: LF: 500kHz 1mW WSPR beaconing

This will be active periodically over the weekend. It would be nice to get a few new reporters spotting me.

73s
Roger G3XBM

--
-------------------------------------------------------------
http://g3xbm-qrp.blogspot.com/
http://www.g3xbm.co.uk
G3XBM    GQRP 1678      ISWL G11088


No virus found in this incoming message.
Checked by AVG - www.avg.com
Version: 8.5.423 / Virus Database: 270.14.29/2455 - Release Date: 10/24/09 06:43:00



[More with this subject...]
<Prev in Thread] Current Thread [Next in Thread>
Previous by Date:  LF: WSPR, Richard Newstead
Next by Date:  Re: LF: OE5ODL F4DTL, F4DTL
Previous by Thread:  Re: LF: 500kHz 1mW WSPR beaconing, Graham
Next by Thread:  Re: LF: 500kHz 1mW WSPR beaconing, Richard Newstead
Indexes:  [Date] [Thread] [Top] [All Lists]