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1. Topband: Extreme directivity (score: 1): Author: "Ford Peterson" <ford@highmarks.com>; Date: Sun, 22 Jul 2007 15:35:10 -0500; Bear with me on this. I am coloring outside the lines again. But I think it's fascinating to consider on Topband. A few months ago, Scientific American ran an article about extremely directional spea; /archives//html/Topband/2007-07/msg00019.html (7,980 bytes)
2. Re: Topband: Extreme directivity (score: 1): Author: "Harold Smith" <w0rihps@sbcglobal.net>; Date: Sun, 22 Jul 2007 19:43:23 -0500; Ford, the tube that ducted the ultra-sonic speaker audio will direct all kinds of audio. I didn't read the article but I don't see why they would modulate an ultra-sonic signal. Audio frequencies sh; /archives//html/Topband/2007-07/msg00020.html (7,625 bytes)
3. Re: Topband: Extreme directivity (score: 1): Author: "Keith Jillings (G3OIT)" <keith.g3oit@jillings.org.uk>; Date: Mon, 23 Jul 2007 01:25:30 +0100; I noodled about the same idea a while ago. Why not go the whole way, and modulate a laser beam with the 1.8MHz signal? How much of the laser beam would radiate my 160m signal? And over what distance?; /archives//html/Topband/2007-07/msg00021.html (7,684 bytes)
4. Re: Topband: Extreme directivity (score: 1): Author: "Dan Zimmerman N3OX" <n3ox@n3ox.net>; Date: Sun, 22 Jul 2007 23:47:31 -0400; "The trick was to modulate the ultrasound at sonic rates. The directivity of the ultra-sound speaker was intact. And the ear would hear the sonic modulation directly." That's not the trick. W0RI is r; /archives//html/Topband/2007-07/msg00022.html (8,560 bytes)
5. Re: Topband: Extreme directivity (score: 1): Author: "Michael Tope" <W4EF@dellroy.com>; Date: Sun, 22 Jul 2007 20:51:31 -0700; The only reason the ultrasonic system works is that there is a non-linear interaction between the ear and air around it that effectively demodulates the signal. The important thing to understand is t; /archives//html/Topband/2007-07/msg00023.html (10,833 bytes)
6. Topband: Extreme directivity (score: 1): Author: Bruinier@t-online.de; Date: 23 Jul 2007 09:18 GMT; Hi Ford, I'm active on 432 EME and topband (both CW only). For 432 I have a 16 long yagi array. The (audio) principle described in the SciAm article would solve all my topband problems. BUT: The AUDI; /archives//html/Topband/2007-07/msg00025.html (7,686 bytes)
7. Re: Topband: Extreme directivity (score: 1): Author: "Raoul Coetzee" <raoulc@smmcape.co.za>; Date: Mon, 23 Jul 2007 12:20:25 +0200; spur When the 432 Mhz is modulated by the 1.8 Mhz thats what you will get , a 1.8mhz modulated 432 carrier,plus the two sidebands (or more, depending if the 1.8 mhz signal is also modulated) The ant; /archives//html/Topband/2007-07/msg00026.html (9,673 bytes)
8. Re: Topband: Extreme directivity (score: 1): Author: "Jim Brown" <jim@audiosystemsgroup.com>; Date: Mon, 23 Jul 2007 08:43:09 -0700; Yes. AND -- pro audio is the world where I work. This ultrasonic concept was demonstrated at least 20 years ago, but I don't know of any use of the technique in real world systems. One of the problem; /archives//html/Topband/2007-07/msg00027.html (8,838 bytes)
9. Re: Topband: Extreme directivity (score: 1): Author: "Ford Peterson" <ford@highmarks.com>; Date: Mon, 23 Jul 2007 11:18:36 -0500; Once again you guys have proved to me that I should keep my day job and forget about my fascination for theoretical physics. The SciAm article producing the inspiration was in the May 2007 issue, pg; /archives//html/Topband/2007-07/msg00028.html (10,302 bytes)
10. Re: Topband: Extreme directivity (score: 1): Author: Les Kalmus <w2lk@earthlink.net>; Date: Mon, 23 Jul 2007 17:20:56 -0400; Ford, You need to get a radio. You definitely need more to do : ) 73, Les _______________________________________________ Topband mailing list Topband@contesting.com http://lists.contesting.com/mailm; /archives//html/Topband/2007-07/msg00029.html (11,241 bytes)
11. Re: Topband: Extreme directivity (score: 1): Author: "Tom Rauch" <w8ji@contesting.com>; Date: Mon, 23 Jul 2007 21:37:01 -0400; Ford, The answer again is a definite NO, we cannot generate a new frequency unless there is a non-linear system that behaves as a mixer somewhere. When or if it does mix, it re-radiates with the con; /archives//html/Topband/2007-07/msg00030.html (9,402 bytes)

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