mashoo
mashoo

inverted vee antenna

If you haven’t seen my kite-portable page, check it out. Also, see details of my lightweight inductors.

A kite is anchored to two dog stakes about 106 metres apart. Each of the two flying lines has one leg of a 78-metre doublet running alongside it, which is anchored with fishing line to one of the dog stakes. The station sits under the apex, with 30 metres of open-wire feeder connecting it to the centre of the antenna.

These photographs were taken on my first expedition. There was sometimes a lot of crackling, probably due to loose connections and the occasional short-circuit in the open-wire feeder. For my second expedition, in the evening two days later, I corrected the loose connections, but the short-circuits kept cropping up, usually after the kite had come down and bunched up the feeder. And so I would like to try insulated wire.

Edit 2012-07-09: Coaxial cable should be impervious to the rise and fall of the kite. Perhaps I could make some from aluminium wire, aluminium foil and PVC sleeving and install a remote-controlled matching network at the top.

The kite’s erratic flight on that second trip reminds me that sled and parafoil kites are less stable than other types in gusty winds.

In order to protect the antenna and feeder from breakage in a gust of wind (and from flying away if the kite were to break free), some elastic device at the apex might be useful. Attached between the flying line and the feeder, it might cushion the effect of a gust and, if weaker than the feeder, break under emergency conditions, allowing the metal wires to remain with the station.

Here is the NEC2 model I devised for this antenna (using xnec2c). It behaves like a half-wavelength dipole on top band, and retains a usable NVIS characteristic up to about 10 MHz.

GW     1    31  0.00000E+00  0.00000E+00  3.00000E+01  0.00000E+00  3.40000E+01  1.10000E+01  5.00000E-04
GX     0    10  0.00000E+00  0.00000E+00  0.00000E+00  0.00000E+00  0.00000E+00  0.00000E+00  0.00000E+00
GE    -1     0  0.00000E+00  0.00000E+00  0.00000E+00  0.00000E+00  0.00000E+00  0.00000E+00  0.00000E+00
EX     0     1     1      0  1.00000E+00  0.00000E+00  0.00000E+00  0.00000E+00  0.00000E+00  0.00000E+00
FR     0   100     0      0  1.00000E+00  2.92929E-01  3.00000E+01  0.00000E+00  0.00000E+00  0.00000E+00
NH     0     0     0      0  0.00000E+00  0.00000E+00  0.00000E+00  0.00000E+00  0.00000E+00  0.00000E+00
NE     0    10     1     10 -1.35000E+00  0.00000E+00 -1.35000E+00  3.00000E-01  0.00000E+00  3.00000E-01
RP     0    19    37      0  0.00000E+00  0.00000E+00  5.00000E+00  5.00000E+00  0.00000E+00  0.00000E+00
GN     0     0     0      0  1.20000E+01  5.00000E-03  0.00000E+00  0.00000E+00  0.00000E+00  0.00000E+00
LD     5     1     0      0  5.96000E+07  0.00000E+00  0.00000E+00  0.00000E+00  0.00000E+00  0.00000E+00
EN     0     0     0      0  0.00000E+00  0.00000E+00  0.00000E+00  0.00000E+00  0.00000E+00  0.00000E+00