Contest Club
QRV since 1993.


The 80 meter band is relatively "wide": It spans 3,5 till 3,8 MHz, so the band width is almost 10%. To maintain an acceptable match without tuning, the width/length ratio can be reduced by using a "thick" dipole. This can be constructed in the form of a cage (4 wires, spread by plastic hoops). It gives an SWR of less than 1.5 across the whole band. We built a dipole this way and some pictures are found here. As always, we made sure that the feed point is perfectly symmetrical, and perfectly matched to 50 Ohms.

Some construction details:
  • Each radiator is 18,50 meters long. Use a VNWA to adjust the length to have 0 (zero) reactance. Adjust the slope of both radiators to get 50 Ohms (remember, a dipole has a radiation resistance of 72 Ohms when spread horizontal. By reducing the top angle, the radiation restance drops). In our case, we found a top angle of about 120 degrees, see photos.
  • The "cages" are made of one heavy and 3 small wires (to avoid twisting in the wind).
  • The hoops are 50 cm diameter.
  • There is one stretch-resistant Parafil wire in the center to absorb the forces of the wires.
  • VSWR is better than 1:5 for the full range of 300 Kcs

A short video with the dipole in 90 Km/h wind.


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