Antenna Work at KT4ZB’s Contest Station

Yesterday afternoon I joined Bill – K4WP, Kevin – KW4B, Ken – W4JKG, Lester – KF4JBQ and other area hams (I’m sorry – I can’t remember everyone!) at Jere – KT4ZB’s house to do some antenna work for his contest station.  While I was there, work was being done on an antenna that I wasn’t familiar with; Jere’s old 40 Meter Bobtail Antenna was being taken down and a new one put up in its place. Other plans were to work on an 80 Meter dipole and to straighten out an element of one of his beams that had been knocked askew when a tree limb brought one of the wire antennas down on it.

Kevin – KW4B using his potato gun to launch a pull rope into a tree for one end of the 40 Meter Bobtail antenna.
Kevin – KW4B (left), Jere – KT4ZB (right), and another ham (I’ve forgotten your name and callsign, I’m sorry!) reel the pull rope in after shooting it over a limb.
Bill – K4WP and Ken, W4JKG
Discussing placement of the other end of the 40 Meter Bobtail.

I had to research the Bobtail Antenna when I came home because it I had never heard of one before.  A Bobtail is composed of two horizontal elements approximately 1/2 wavelength long and three vertical elements approximately 1/4 wavelength long.  One of the vertical elements hangs from the center of the two horizontal elements and the other two hang one at each end of the horizontal elements.  The antenna is fed at the center vertical element.  With the Bobtail that Jere is using, it will also be grounded at the feed-point; there was discussion of using some screen along with the ground rod and I’ve also read in my research about others using radials from the ground rod (living right along the marsh, Jere’s yard may have good ground and not need the screen or radials).

Bobtail Antenna diagram from WB3AYW’s article on Hamuniverse.com (http://www.hamuniverse.com/wb3aywcurtainantennas.html) showing formulas used for calculating the elements.
This diagram from SM0DTK’s website (http://hem.passagen.se/sm0dtk/antennas.htm) shows how Jere’s Bobtail will be fed from the bottom of the center element and connected to a ground rod.

Once I read WB3AYW’s article on Hamuniverse.com I understood why Jere uses this type of antenna for his station.  Jere is a DXer and contester; the Bobtail Antenna is effective on low angle signals making it a good antenna for working stations at long distances so it is a good DX antenna.  In my reading at W7HTJ’s website, I learned that one disadvantage of the Bobtail is that it has a somewhat narrow bandwidth, so with it being a bidirectional antenna you have to make sure that you have the antenna orientation right or you may not have as much success with it.

I’ll be the first to admit my technical knowledge of the hobby is limited and I like to take advantage of opportunities like yesterday afternoon. I’m glad Jere invited us over to help because yesterday I got to learn about something new.  I always enjoy getting to do something with hams like Bill and Ken because of their knowledge of the hobby; Bill has a wealth of experience and Ken is one the radio club’s license class instructors.  One of the great aspects of amateur radio is that it seems that you never stop learning.

 

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