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## [TowerTalk] Fwd: Dielectrically lenghtening the boom

 To: towertalk@contesting.com [TowerTalk] Fwd: Dielectrically lenghtening the boom hanslg@aol.com Tue, 22 Dec 2009 23:02:57 -0500 mailto:towertalk@contesting.com>
 ``` One thing everyone seems to forget is how to get the wave out of the dielectrics after it is generated by the very much smaller antenna. You could reduce the size major if you surround it with water (e=80). The wave will be nearly totally reflected when it reach the surface between water and air (and it is air we will have it to end up in). It seems that do this for high frequency such as cell phones etc is feasible but hardly for an 80 or 160 meyer application. de Hans - N2JFS -----Original Message----- From: David J. Sourdis - HK1A To: towertalk@contesting.com Sent: Sat, Dec 19, 2009 7:15 am Subject: Re: [TowerTalk] Dielectrically lenghtening the boom My bad, I was maybe thinking about VF < 1.0. I meant dielectric constant > 1.0 instead of <1.0. Back to the shortened boom Yagi discussion, Dan said something that I will put in my words: That the wave propagating inside a coax "sees" the space contained between the inner conductor and the shield filled with the dielectric material. What if a tube with a few wavelenghts section, like a big waveguide (circular, rectangular or elliptical section), is filled with dielectric material and the antenna is placed exactly centered along the axis of the tube. I guess that mathematically there is a mínimum lenght from where the modeling can approximate the behavior of the antena as if it were in a infinite lenght medium. Would then the antenna "see" that is contained in an "infinite" block of material? Of course this would not be practical on HF or even VHF. It's just for the sake of learning. David HK1A EC5KXA > Date: Fri, 18 Dec 2009 21:15:45 -0800 > From: jimlux@earthlink.net > To: ai.egrps@gmail.com > CC: towertalk@contesting.com > Subject: Re: [TowerTalk] Dielectrically lenghtening the boom > > Andy wrote: > >> Take a Yagi, and fill the space between elements with a material which its > >> dielectric constant is less than 1.0 (air's). > > > > You probably meant to write "greater than 1.0". I'm not aware of materials > > with dielectric constants less than 1.0. > > > > There are composite materials which have apparent permittivity <1 for > limited frequency ranges. > _______________________________________________ > > > > _______________________________________________ > TowerTalk mailing list > TowerTalk@contesting.com > http://lists.contesting.com/mailman/listinfo/towertalk _________________________________________________________________ Windows Live: Keep your friends up to date with what you do online. http://www.microsoft.com/middleeast/windows/windowslive/see-it-in-action/social-network-basics.aspx?ocid=PID23461::T:WLMTAGL:ON:WL:en-xm:SI_SB_1:092010 _______________________________________________ _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk _______________________________________________ _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk ```
 Current Thread [TowerTalk] ride up with the load, Drax Felton Re: [TowerTalk] ride up with the load, Roger (K8RI) Re: [TowerTalk] ride up with the load, K1TTT [TowerTalk] Dielectrically lenghtening the boom, David J. Sourdis - HK1A Re: [TowerTalk] Dielectrically lenghtening the boom, Dan Zimmerman N3OX Re: [TowerTalk] Dielectrically lenghtening the boom, David J. Sourdis - HK1A Re: [TowerTalk] Dielectrically lenghtening the boom, jimlux Re: [TowerTalk] Dielectrically lenghtening the boom, Andy Re: [TowerTalk] Dielectrically lenghtening the boom, jimlux Re: [TowerTalk] Dielectrically lenghtening the boom, David J. Sourdis - HK1A [TowerTalk] Fwd: Dielectrically lenghtening the boom, hanslg <= Re: [TowerTalk] ride up with the load, Robert West