Topband: vertical 160/80m

[john battin]

I have used a 90 foot vertical with a tapped loading coil for 160 and a series C for 80. On 80 it is a bit better in side/by/side comparisons with a 1/4 wave vertical over an identical 100 radial field. It also does well on 160. It is also simple.
John  K9DX
  ----- Original Message ----- 
  From: Tom Rauch<mailto:w8ji at contesting.com> 
  To: Ryszard Tymkiewicz<mailto:rtym at ippt.gov.pl> ; topband at contesting.com<mailto:topband at contesting.com> 
  Sent: Saturday, April 17, 2004 6:54 AM
  Subject: Re: Topband: vertical 160/80m


  > I know Bob W7LR is using 90 ft verical for both bands but maybe its
  > better /for 80m/  to use "isolating trap" between the hat and the top of
  the mast?
  > I will build in a Summer so I still have a time but its important for me
  to know
  > what the height will be the best so which construction to choose.

  Rys,

  The performance difference between a base loaded 90 ft vertical and top
  loaded is unimportant if the ground system is good. Loading location is not
  so important.

  With noticeable ground losses, you would want radiation resistance as high
  as possible. That occurs when ampere-feet of antenna is as large as
  possible, so you want current maximum over the length of the antenna as long
  as that does not increased loss in a loading coil or something similar.

  The problem is mostly on 80 meters. I have had poor results with 1/2 wl
  verticals on 80. Even on 160 my 318 foot tower is not much better than a 1/4
  wl vertical, and gives up a good amount of performance at modest distance or
  at sunrise or sunset.

  On 80 meters, I have found this worse. Some of my poorest 80m verticals have
  been 1/2 wl or taller verticals.

  If you find performance on 80 lacking, you could use a 1/4 wl skirt for 80
  meters and feed it. Then you do not need traps, and the bandwidth would be
  much wider. But I would still try the vertical and see how it behaves for
  you without anything special. You could install the skirt, and not connect
  it unless needed. It would allow you to do an A to B test and tell us all
  the results.

  73 Tom


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