Here's a quick example from EZNEC: A 33 ft vertical wire on 3.5 MHz will show an impedance of about 7-j384 ohms. That's a typical "Marconi" antenna.
Add one 33 foot horizontal wire at the top to make an Inverted L and the impedance jumps to 18-j23 ohms. Note that while the resistive component as increased 2-1/2 times the reactance has also dropped; both positives in improving efficiency. The pattern is now a skewed mix of horizontal and vertical radiation. Now add a second 33 foot horizontal wire at the top running 180 degrees away from the first (that is, there is now a 66 foot horizontal wire connected at its center to the 33 foot vertical wire). The impedance raises further to about 22+J79 ohms. The top wire radiation cancels nicely (being out of phase) and the radiation pattern looks very typically vertical again. Top wire angles of other than 180 degrees (straight line) will produce odd mixed results of horizontal components. Ron AC7AC -----Original Message----- From: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of WILLIS COOKE Sent: Monday, December 20, 2010 10:36 AM To: Edward Dickinson, III; elecraft@mailman.qth.net Subject: Re: [Elecraft] Inverted-L (was OT: Vertical antenna) Dick, my research would say probably not. The exception would be if your lot is such that you could run more than one shorter wire and can't run a single one. Also you might be able to make a capacity hat with the top guys broken by insulators and not need another support. The antenna would then be known as a T top or Capacity Hat type vertical. In any case the horizontal wires do not contribute much to the radiation pattern but do help raise the radiation resistance, increase the band width and bring the short vertical wire to resonance. The choice seems to me to be primarily for installation convenience which varies from QTH to QTH. Willis 'Cookie' Cooke K5EWJ ________________________________ From: "Edward Dickinson, III" <softb...@windstream.net> To: elecraft@mailman.qth.net Sent: Mon, December 20, 2010 12:16:53 PM Subject: Re: [Elecraft] Inverted-L (was OT: Vertical antenna) On the Inverted-L off topic, is there anything to be gained, or lost for that matter, by having more than one of the horizontal portion of the antenna? 73, Dick - KA5KKT ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
