rinioth: (radio)
[personal profile] rinioth
About three and a half years ago I constructed a 60m EFHW antenna for my home amateur radio station, see here and here.

The antenna has worked extremely well since then and using it I've worked stations on the 60m band as far away as the north cape of Norway and the Alicante region of south east Spain.

However the antenna, in common with all End Fed Half Wave antennas, has one drawback it has a very narrow bandwidth. To some extent the Antenna Tuning Unit (ATU) in my radio overcomes this but with the antenna set up to be resonant in the middle of the 60m amateur allocation the ATU struggles at the extreme edges of the band.

The answer is to have two antennas, one for the lower portion of the band and one for the upper. Well, not quite, I've rebuilt the feed-point impedance matching unit so that it is switchable using a relay to add some extra capacitance. The relay will be operated from the operators position at the radio using a multi channel remote antenna control system I've designed and built. This will switch between the two antennas, 60m and 80m, that share the same feeder coaxial cable and will also operate the tuning relays on both antennas.

switchable EFHW unit

The relay is in the lower right corner of the box with the small 10pF capacitor that it switches in and out of circuit just above it in the photo. The resistor and wire between the antenna and counterpoise terminals is part of the testing set-up to get the unit roughly tuned to the correct frequency.

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Colin

September 2017

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