Topband: Topband Digest, Vol 113, Issue 46

[wa3mej at comcast.net]

Jeff, 

  I believe the prop mode you are taking about it called "ANTIPITAL PROPAGATION"  it is like a focusing mirror.  There is a story about Ben Franklin in one of the early sessions of congress.  Being the scientist he was he found a spot in the capitol, a particular location where he would place is seat. He did this because he could hear his adversaries on the other side of the room plotting their strategies. Why did this happen well because the ceiling of the capitol was a giant dome and acted like a parabolic reflector and the audio bounced off the ceiling to his ears.  Dont believe me.. Go to Captian Georges resturant in Virginia beach and sit in one of their domed rooms out front and you can hear people talking on the other side of the room.  I think there is a more comon name for this mode but cant remember what is is now.. and there have been several masters research papers published about it.  I have one of them published by Pipp et al but have never scanned it in .. it is somewhat large.  I intend to put it on my web sit at some point... a job for the future I guess. 



By the way this works for any place in the world .. supposedly.. take your lat/lon and subtract 180 deg from it and if it hits land your in luck .. look for stations from that area.  Hummm I wonder if the other name was Antipode focusing.. not sure anymore. 



GL 



Jim 





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Message: 9 
Date: Thu, 31 May 2012 15:24:37 -0700 (PDT) 
From: Jeff Woods <jmwooods at yahoo.com> 
Subject: Re: Topband: RI1ANF 
To: "Topband at contesting.com" <Topband at contesting.com> 
Message-ID: 
<1338503077.85738.YahooMailNeo at web39401.mail.mud.yahoo.com> 
Content-Type: text/plain; charset=iso-8859-1 

Here's an interesting story: 

In the early 90's, I worked as a ship-board radio officer.? At one of the training conferences, I met a fellow RO who also worked at the McMurdo Antarctic base when he wasn't on ships.? During one of our (many and frequent) conversations after hours at the hotel bar, he mentioned an odd propagation mode at 5 kHz which only seemed to be present from pole-to-pole.? The physics of this propagation are still unclear to me, but the salient point is that he also described the antenna.? 


It was a simple dipole, cut for resonance, and strung for miles along the icecap.? Ice is a good insulator, and the ice cap is thick enough to give a "ground mounted" dipole reasonable height even at VLF.?? 

At 160m, a dipole on the ice would act as though it were essentially in free-space. 

Feel free to fact check me on this.? I was young.? We were sailors.? And we were drinking.? :-)? But it does bode well for helping Herb get his Antarctic merit badge some day. 


-Jeff? W0ODS