Hi Wes,
The WWV half wave vertical is much like the "Happy Accident Ground Plane" described in January 1957 QST that uses only four sloping radials, sloped downward 30 degrees to produce direct 50 ohm feed point impedance. The sloped radials make them into radiators, hence the feed point impedance is raised to 50 ohms with the appropriate slope. The feed points of the WWV antennas are 1/4 wavelength high, but I'm sure the performance would be little affected by lowering it somewhat. This antenna isn't quite a balanced half wave vertical, it isn't quite a ground plane, and it isn't quite a sleeve dipole but it definitely works very, very well. I used a 20 meter "Happy Accident Ground Plane" mounted 50 feet up in a maple tree for many years when I was in Rhode Island during the 1960s and worked the world with it. 73 Frank W3LPL ----- Original Message ----- From: "Wes Stewart" <[email protected]> To: [email protected] Sent: Monday, February 13, 2017 6:43:29 AM Subject: Re: [Elecraft] EFHW >From the WWV site: The WWV antennas are half-wave vertical antennas that radiate omnidirectional patterns. There are actually five antennas at the station site, one for each frequency. Each antenna is connected to a single transmitter using a rigid coaxial line, and the site is designed so that no two coaxial lines cross. Each antenna is mounted on a tower that is approximately one half-wavelength tall. The tallest tower, for 2.5 MHz, is about 60 m tall. The shortest tower, for 20 MHz, is about 7.5 m tall. The top half of each antenna is a quarter-wavelength radiating element. The bottom half of each antenna consists of nine quarter-wavelength wires that connect to the center of the tower and slope downwards to the ground at a 45 degree angle. This sloping skirt functions as the lower half of the radiating system and also guys the antenna As a side note, several years ago when my late wife and I were still traveling around in an RV we were near Ft. Collins. As I have done with other stations I telephoned the site and asked whether I could get a tour. The NIST guy was incredulous and said that no way did they give tours. I said, pity, I'm an engineer and ham and am disappointed. He thought for moment and then said, "Actually, we have a contractor doing some work here and the gate is unlocked. If you were to drive in and look around you wouldn't be bothered, but please stay in your car." So we did. The WWVB antenna was pretty impressive, but nothing like NAA in Cutler, Maine. Wes N7WS On 2/12/2017 8:56 PM, Fred Jensen wrote: > KFBK in Sacramento uses [or used, my info is a few years old] a center-fed > half-wave vertical ["Franklin"] antenna, said to be the only one left. It's > ... interesting. [:-) KFBK is also the originator of the first out-phasing BC > TX which became the RCA Ampliphase [or Amplifuzz if you ever had to get one > to > pass PoP]. KFBK is also the radio birthplace of Rush, "Bloviator in Chief," > although that's probably far less important than the Franklin. There was a > radial field under the Franklin, it may have rusted into oblivion by now, I'm > not sure it was all that important, it's located in the flood plain north of > Sacramento ... moderately wet, they grow rice in the area. > > 73, > > Fred ["Skip"] K6DGW > Sparks NV DM09dn > Washoe County ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
