Hi Don,
Of course you're exactly correct. The peak horizontally polarized radiation with respect to the axis of a long wire steadily decreases from 90 degrees for a 1/2 wavelength or shorter wire to about 50 degrees for a 1 wavelength wire, then very slowly decreases to 35 degrees for 2 wavelengths, 30 degrees for 3 wavelengths, 25 degrees for 4 wavelengths, etc. As the length of the wire increases, the direction of the main lobe for horizontal polarization more closely approaches the direction of the wire but in never gets closer than 15-18 degrees from the end of the wire for any practical wire length. There's always a deep null off the end of the wire for horizontal polarization no matter how long the wire is. If a long wire antenna is carefully designed and constructed to carry a pure travelling wave, the angle of the main lobe does NOT change relative to a classic long wire antenna; however, the amplitudes of the successive lobes can be greatly suppressed in a very carefully engineered antenna. Its extremely difficult to achieve travelling wave performance in a long wire antenna except for a few special cases: - a long wire with a resistive termination connected to a 1/4 wavelength termination wire, - a terminated rhombic antenna, - a Beverage antenna close to the ground, and - a resistively terminated vertically polarized half-rhombic antenna (sometimes referred to as an inverted-V antenna in professional antenna engineering circles). 73 Frank W3LPL ----- Original Message ----- From: "Don Wilhelm" <donw...@embarqmail.com> To: elecraft@mailman.qth.net Sent: Thursday, January 11, 2018 5:09:04 AM Subject: Re: [Elecraft] Long wire antennas Frank and all, While it is true that radiation off the end of a long wire is a deep null, The maximum radiation will be at an angle to the wire greater than 1/2 wavelength (less than 90 degrees). That angle will depend on the length relative to wavelength. A look at the radiation pattern of long wires and other Traveling Wave antennas will reveal that fact. The rhombic antenna and V-beams use that characteristic for their gain and directionality. 73, Don W3FPR On 1/10/2018 11:40 PM, donov...@starpower.net wrote: > Ron, > > > What you've come to understand is absolutely false except for the > special case of a long wire close to the ground. That special case > is called a Beverage antenna that radiates vertically polarized > radiation off the ends. > > > When you raise a long wire antenna more than about 0.05 wavelengths > above the ground, horizontal polarized radiation becomes dominant > and the radiation pattern always has a deep null off the ends. > > > 73 > Frank > W3LPL > > ----- Original Message ----- > > From: "Ron D'Eau Claire" <r...@cobi.biz> > To: "Elecraft Reflector" <elecraft@mailman.qth.net> > Sent: Thursday, January 11, 2018 4:08:40 AM > Subject: Re: [Elecraft] Long wire antennas > > Understand that a true "long wire" (greater than 1 wavelength) starts to be > directional off of its end (if fed at one end, that's the opposite end). > > 73, Ron AC7AC ______________________________________________________________ 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 Message delivered to donov...@starpower.net ______________________________________________________________ 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 Message delivered to arch...@mail-archive.com
