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Using a Fan or Bowtie Dipole to Cover 75/80 Meters

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by W5JD, Jan 7, 2019.

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  1. W5JD

    W5JD Ham Member QRZ Page

    I am currently running an Inverted-V for 75/80 meters. I have a VSWR of 1.1:1 at 3.8 MHz but my automatic antenna tuner will sometimes not tune the band extremes. After researching the different methods of increasing the bandwidth of a dipole, I have decided to try a Fan Dipole to cover 3.6 to 4.0 MHz, hopefully at a VSWR of 2:1 or less.

    I have been trying to find the QST May 2005 article "The Fan Dipole as a Wideband and Multiband Antenna Element" on the internet without success. Anyone have that article or other information regarding wideband Fan or Bowtie Dipoles?

    I want to feed the antenna with 50 ohm coax. I will be using EZNEC+ Version 6.0 to predict the feed point impedance for my mounting height of 130 feet.

    At this point I am not sure if I want to design the antenna with equal length or staggered length wires. Any preference for a Fan Dipole or with the ends connected as a Bowtie? I have the ARRL Antenna Book and looked at the Fan Dipole with 3 wires on each side cut for the low, middle, and high end of the band. Any suggestion for the design?

    Thanks in advance,

    Terry, NZ5E
     
  2. W1VT

    W1VT Ham Member QRZ Page

    K0UO likes this.
  3. N2EY

    N2EY Premium Subscriber QRZ Page

    Many years ago, I did some work on a "bow-tie" dipole for 80/75 for Field Day. As the name suggests, this was a horizontal dipole with two wires on each side, like this ><, fed in the center with 50 ohm coax. The ends were about 8 feet apart.

    The following was learned:

    1) It was possible to get better than 2:1 SWR from band edge to band edge with this design, with the dipole up about 50 feet.

    2) The wire lengths were quite a bit shorter than the usual formulas predicted. I don't recall exact numbers.

    3) Some experimentation was needed to find the right dimensions.

    4) Like most antenna projects, it was more about mechanical design than electrical.

    73 de Jim, N2EY
     
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  4. WA7ARK

    WA7ARK Ham Member QRZ Page

    I get QEX and read this article about how to make a dipole that covers the whole 75m/80m band. This really works.... Here is a simulation of a 40m version of this idea I am planning to build for my own use...

    br.png

    If you are interested, I can scale it to 75/80m and re-run the optimizer. You would have to provide some details about how you plan to deploy it.
     
    Last edited: Jan 7, 2019
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  5. AC6LA

    AC6LA Ham Member QRZ Page

  6. WA7ARK

    WA7ARK Ham Member QRZ Page

    The plot above uses 90ft of RG8 at the feedpoint (1/2wl), followed by 22.5ft of RG11(1/4wl), followed by any convenient length of RG8 to get to the shack. The wire is 67ft long, apex is at 50ft agl, and the wire ends are at 36ft agl, above 2mS/13 dirt.
    I was busy at the time, and didn't read all of that thread. There is a wealth of info there.
     
  7. WA7ARK

    WA7ARK Ham Member QRZ Page

    Here is what adding 107.8 ft of Belden 9913 followed by 58.ft of Belden 8213 followed by some more Belden9913 will do the SWR of a 50ft high 126.6 ft horizontal dipole 50 ft agl above poor (2mS/13) dirt.

    80s.png
     
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  8. W5JD

    W5JD Ham Member QRZ Page

    Thanks to all that responded and sorry for my delayed response. Life and business got in the way of playing radio.

    Please see my new thread "75 meter Bowtie with 60 Meter Coupled Resonator". I am hoping that someone can help me with the idiosyncrasies of EZNEC to improve on my model.
     
  9. W5JD

    W5JD Ham Member QRZ Page

    I will mount the Bowtie at the 130 feet level on my tower where there is an Anti-Torque device, so I will have a strong support structure. I have plenty of trees to tie off to and a friend with a bucket truck to mount pulleys in the trees at 60 feet. The mechanical challenge will be mounting the 60 meter Coupled Resonator at a uniform distance below the center wire of the 75 meter Bowtie.
     
  10. W5JD

    W5JD Ham Member QRZ Page

    I had already read this material and I am impressed with your work! Please see my new thread and let me know if you see something obvious that will improve my model.
     

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