NVIS Super-Gainer Antenna

For the club's August "field day" members built and tested an NVIS antenna. This was prompted by the success of a relatively low G5RV antenna on 40 meters at the Broadwater Carnival.

Following the design published at HamUniverse club members ended up with a folded dipole 64ft 4 inches long with 10 inch spacing, driven via a 1:1 choke balun at a height of 8 feet with low SWR in the 40 meter band. Below the driven element were three ground radials that were 5% longer than the driven element. These were suspended above the ground to minimise ground losses.

NVIS Folded Dipole

Members were able to work stations around the UK and Ireland and into Germany with good signal reports with a very low background noise level.

G0JXX operating NVIS on 40m

The folded dipole could be used at a greater height to give lower angle radiation, but then would require a 4:1 balun at the feed point, as the feed impedance would rise to nearer 300 ohms.

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