WiMo Antennen und Elektronik GmbH
Am Gäxwald 14, D-76863 Herxheim Tel. (07276) 96680 FAX 9668-11
http://www.wimo.com e-mail: [email protected]
•
Kelemen Trap Dipoles
Kelemen-Antennas are wire antennas with traps made of Teflon insulated Coax.
Trap Antennas – What Does that Mean?
By inserting traps into both halves of a dipole further resonances can be obtained. Trap antennas
are mostly somewhat shorter than full size dipoles and offer multi band operation where limited
space doesn't allow larger antennas.
With trap antennas, however, you have to consider the weight of the traps, as they are mostly
rather heavy and increase the mechanical load considerably causing the antenna to sag.
Trap antennas, however, are no broad-band antennas. The SWR rises quickly when working off
the resonant frequency and an antenna tuner may possibly be required.
The location of a trap antenna is more critical than that of a mono-band dipole. Just as any dipole,
the antenna should be placed as high and unobstructed as possible to avoid shifting of the
resonant frequencies. Install it well away from buildings and similar structures. For the design of
Kelemen-dipoles a reference height of 10 metres above ground has been assumed.
Their coaxial traps are much lighter than conventional traps making it easier to keep the antenna at
a more effective average height.
Kelemen-Antennas are most suitable for portable operations because of their low weight. In most
cases they can be simply supported by a single glass fibre pole.
The special traps of Kelemen-Antennas have a high Q and therefore low losses.
If you do not have enough space for a full-size dipole, you can use a shortened dipole with loading
coils made of Teflon cable. However, shortening reduces the usable bandwidth and an antenna
tuner may be required.
Like all Kelemen-Antennas the shortened versions are lightweight, as well as fully temperature-
resistant and weatherproof.
Kelemen-Antennas are being manufactured from high-quality materials. All cases are milled from
weather-proof Polycarbonate. Nuts, bolts and clamps are all made of stainless steel. Baluns are
cased in bolted transparent cases of weather-proof Polycarbonate. In spite of the higher
manufacturing costs they are not potted in sealing compounds to enable you to fix the balun
yourself in the rare case of a failure. Furthermore it saves about half its weight. As condensation
cannot totally be avoided, the bottom of the balun has a drain hole providing ventilation at the
same time. All baluns come with a lug for easy mounting.
Included in delivery: complete antenna ready for operation, including balun with SO-239 socket
and egg insulators.
As required, we offer models from 200 Watts to 2000 Watts.
Power ratings refer to PEP in SSB and actual Morse-keying (not permanent key down) in CW. All
these ratings call for an antenna impedance of 50 ohms (more about that below).
Wire Antennas in Inverted-Vee Configuration
I
f for lack of space an antenna cannot be installed horizontally, the inverted-vee configuration is a
useful alternative. Instead of the typical directional pattern of a dipole the radiation is almost
omnidirectional, and only one single central support is required. Preferably, the apex angle should
be between 90 and 130 degrees and not less than 75 degrees. Keep the ends of the dipole well
above ground by extending them with some non-conductive line.
