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Technical informations Concept The principle of
this antenna is very simple: a normal 3 element Yagi with Director and
Reflector in a V-shape.
The resulting antenna can be built using wire elements strung on a
supporting cross.
The
creator of this antenna system is Dick Bird G4ZU, in the ARRL Antenna
Compendium Vol.3 he published this antenna project to single-band 10 meters
and named it “Bird-Yagi”.
The
concept behind this antenna was developped by Cornelius Paul "Con",
DF4SA. He has done a lot of work and development to a multi-band version he
called "SPIDERBEAM". Antenna parts
The antenna is
constructed with a 7+ meter Vertical rod, 4 Horizontal rods at 2.75 meters
each on a cross system all attached with simple copper-wire.
Antenna
requirements summary This antenna is
perfect for Dx'peditions as it is: 1. Light (only
2,7 kg including a 8 meter fibreglass pole) 2. Easy to
errect (no bolts or screws/5mins max) 3. No impedance
adaptor or balun required. 4. Max power
capability of 2kw. 5. Tough and
durable (professional fisherman type fibreglass rods used) 6. Easily
transportable (folds down to 1 meter) When installing
beam antennas it is better to get them errected as high as possible, because
an antenna with less gain errected as high as possible will produce a better
signal than one of a higher gain errected at a lower height. It´s low weight
makes it much easier to put the skypper-beam higher up and choose better
locations. Use it while
travelling, activate a nearby mountain, island, castle or lighthouse, put it
on the roof for a contest weekend, this antenna goes everywere you need high
gain and very good performance! Antenna
Performance forward gain is about 5dBd
(7,2dBi) in free space (= 12dBi in 8m height above ground) and stays nearly
constant over the whole band.
These are the simulations in
NEC2 with the software “Antenna Optimizer”. Like you can see, the pattern
diagram is very selective, with noteable front-to-back performance around
27db . The vertical diagram pattern with the antenna at 8 meters height,
presents the elevation peak at 18° with 12,14 dbi and 5,14dbi at 5°.
Free
Space
Antenna
8 meters above ground Vertical
polarization This is the next development of the Skypper beam: "the vertical polarization"! It's very easy... it´s necessary to use only one 2 arms (and not
4) of the central cross, junted of the vertical pole with a isolant
rubber. Off course the gain are more low of the horizontal polarization, but
the vertical radiation patterns are very interesting.
Avertical polarization: 4 meters above ground Comparsion with
other antennas This is
the comparsion with other antennas ( Dipole, Vertical, X-Beam, Hex Beam,
Moxon, 2&3 element yagis,1-2&3 element Quads). All these
antennas have something they are good at and this type of comparsion does not
necessarily show the best features of each. For example, the X-Beam can have
a low F/B ratio at high gain which I like as a contester; the hex beam construction
lends itself to multi-banding; the Yagi is good for interlacing, the vertical
has good radiation at low angles, some are easier to match impedance,
etc, etc. More informations on: http://www.cebik.com/4.html They
are the parameter charteristic of this antennas, developed with AO
software... All
modeling done in "Free Space", 27.6 MHz, Resonant (reactance=0), Al
6063-T832 tubing, dBi gain units, 20 segments/half-wavelength = ~21" / segment.
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