We built and use at the club station RK0SYY the Telerana antenna modified by
This is a full size logoperiodic antenna which covers the band 14MHz...30MHz. Its gain is about
5 dbd in all this band. SWR not more than 1.2. F/B more than 30 db on 20 and 15 meter bands.
You can see this antenna at the right. (Click the photo to zoom in).
It is really nice but at the same time strange feelings come when we tune in any part of a
band and get SWR less than 1.2!
Hammock - 2 element wire Yagi antenna for 3 bands
This is a fine antenna for field conditions and for work from home.
The antenna was designed by VE7CA who designed
the Telerana modified antenna.
At his site one can find
original description of the antenna.
SWR on all three bands (14, 21, 28) is within 1.0...1.5.
One of the main advantages of the antenna - the quick and ease installation.
We put any mast of 12 meters height. At the top the pulley is fastened.
There is a rope which passes over the pulley
The rope is knotted to the antenna and antnna can be quickly lifted or lowered.
It is important in fields, as weather can change very fast. To lower
the antenna is a matter of several seconds.
Further - only one mast is needed for an installation of the antenna.
In horizontal position the antenna radiates under the big corners to horizon.
If a plane of the antenna to place under a corner to horizon the basic radiation
starts to be lower.
One can move a peg (to which the lower part of the antenna is fastened) from
the mast and the corner of radiation will be easily changed. (see the photo).
The closer a peg to a mast, the closer to horizon will be vertical radiation.
As all antennas radiate to a side opposite of a reflector
it is possible to change a direction of radiation of the antenna
in horizon plane by placing the peg in different places around the mast.
As the antenna is fastened, (as it is seen in the picture), in two points,
it can be turned over on 180 degrees.
This changes very quickly a direction of its radiation on opposite.
When one makes the antenna it is necessary to make sizes such as they are
shown in the figure. First we made it with one reflector - on 14 MHz
and the antenna was tuned in a high-frequency part of 20 meter band.
After addition of reflectors for 21 and 28 MHz antenna begans to resonate
in a high-frequency part of CW part of the band that enables
to provide QSOs in CW and SSB parts of bands.
Resonant curves are flat and SWR at edges is no more than 1.5 .
We call this antenna a Hammock.
By the way in the original antenna two wooden bars of 50 x 50 mm (between
these bars elements are stretched) was used.
We use plastic fishing rods instead. This considerably lightens the antenna.
Elements of the antenna are made from twisted copper wire with
a total diameter of 3 mm.
Spacers among vibrators are made of plexiglass.
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