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The 18m glassfibre pole from SPIDERBEAM - see
http://www.spiderbeam.net (quality and top service by a real Ham!) The
antenna itself is composed of 12m of heavy flexible insulated copper
wire 4mm² section + 7m of same but 2,5 mm² on the top. This 19m wire is
tightly wound around the pole (pitch about 1 turn per 2m). There is no
top hat. SWR <1.3 from 3.6 to 3.8 Mhz. No variation to observe in
function of ground humidity / rain etc.
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A closer look to the base, which is designed for
temporary/portable use. I am using only 3 guy wires (heavy nylon ropes)
about 8m from base. For permanent installation, I would recommend to use
a second set at about 14m high. |
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The 96 radials (each approx 10m long, and 12 of
them are fitted at their end with a copper pipe 30cm long buried in
soil. It is in fact the ground radial system of my Butternut GPA |
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A closer look at the base loading coil. In fact, a
coil is not really needed, but allows to finetune the GPA smoothly. The
coil support is constructed as removable, I am thinking of swapping
another coil for 160m operation. OK, I agree that the copper coil is a
total overkill, but I had this material available for free ;o) |
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Detail of coil mount. It is all made of PVC
rainpipe and accessories available at any DIY shop. |
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The antenna base. It is a piece of steel square
profile 80x80mm and 600mm high where the glassfibre antenna base just
nicely fits. The 'tripod' tubes are all of standard galvanised pipe. |
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Counterweight at base is with concrete tiles of
300x300mm.
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Counterweight support frame construction. This can
be removed from antenna base tripod for transport / storage... |
