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 There’s a lot of truth in the old saying that “If an antenna doesn’t fall down, it isn’t big enough” but we take efforts to minimise repairs and maximise reliability, preferring to build, test and use antennas rather than constantly rebuilding and repairing them, and the same goes for rigs and amplifiers.
The ZL climate is generally kind to us but being a coastal site means we are always at the mercy of storms and salt water corrosion, while UV damage turns new ropes into nasty old string in a couple of years or so.
We are constantly innovating and experimenting with antennas at the club, looking for that elusive combination of directivity (both azimuthal and elevation gain), practicality and reliability. Given the luxury of a lovely hilltop coastal site with a clear 360-degree view to the horizon, a couple of fixed masts and lots of handy tall trees, we prefer typical aluminium Yagi beams (now all monobanders), plus fixed wire beams, loops, verticals and dipoles for the low bands.
Some of our antennas are fixed in place, others are erected just for the contests, field day or DXpedition-style. A home-brew 10m 4-ele beam (above) goes up on a pole just before the contest starts and comes down shortly afterwards, whereas the 20m 3 ele (further above) and 15m 5 ele (below) are permanently installed.
 The 40m quarter wave vertical (right) is erected on a hinged base on top of a large shed - we simply push it up when we need it. The corrugated iron roof makes a good ground plane.
Here’s our antenna selection for the 2010 contest season:
- 160m: nearly-full-sized quarter wave wire vertical in a small copse of trees on a steeply-sloping wooded site, with more than 16 radials;
- 80m: full wave wire loop strung between three trees, mostly in the clear;
- 40m: quarter wave vertical on a tin roof groundplane; full wave loop in the trees; dipole available as backup;
- 20m: homebrew 3 ele monobander (top photos);
- 15m: 5 ele monobander (in place of the tribander shown here, photo to come);
- 10m: homebrew 4 ele monobander (shown above prior to erection).
A spud gun built by Chris ZL2DX is used to get ropes over the tall trees to support various wire antennas. It’s much more effective and accurate than any other method we’ve tried ... if somewhat dangerous (Lee wonders why some of us head for cover when he gets that spud-gunner’s glint in his eye).
The spud (potato) you can just see in this action shot is an environmentally friendly missile: whether it gets stuck in a tree or lands on the ground, it just rots away.
Given that this photo was taken on a bright sunny day, the exposure was probably about 1/400th of a second. The spud appears to have travelled about 25cm in this time, meaning a velocity of approximately 100 metres per second - that’s 225 miles per hour!
Previous antenna experiments at the club have included:
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Simple wire dipoles for 80 and 40m, used as a base comparison for new antennas;
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Top-loaded short sloping vertical for topband - just didn’t radiate competitively;
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A 2-element wire beam for 40m, strung on a rope catenary between two trees. The beam could be reversed simply by flipping it over using ropes. It beamed NE (to W-land) or SW (to Africa). In practice, we found signals were consistently down compared to the 40m loop or a plain dipole, so the wire beam was dismantled. Shame. It was a lot of work to erect but didn’t earn its keep - presumably it was just too low?
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A 3-ele tribander performed as a tribander always does, at least until the coax choke got wet and corroded.
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