Cage antenna
A trap antenna is an antenna that consists of several wires, the so-called trap ropes, which are usually arranged radially symmetrically .
construction
In the simplest case, a trap antenna is a parallel and radially symmetrical arrangement of wires, each of which is carried by a ring at its ends, and which are combined and stretched behind these rings on the outside. The trestle ropes then describe the outer surface of a cylinder between the rings . This arrangement is also known as a cage trap. Alternatively, the wires can also be attached to rings of different diameters with radial symmetry, so that the wires describe the outer surface of a truncated cone . Both antenna structures are reminiscent of fish traps . Dipole antennas with a large bandwidth can be assembled from cage traps . Examples of this are the quadrant antenna , a steep omnidirectional short-wave transmitter antenna in the form of an L-dipole made of two identical cage pots, and the curtain antenna (a directional short-wave transmitter antenna) with several folding dipoles made of cage traps.
A special version of the trap antenna is the flat trap. The antenna wires are arranged next to one another in one plane and are therefore not supported and combined with rings, but with bars.
Another design of the trap antenna is the radially symmetrical vertical arrangement of wires around a transmission tower or transmission mast . The trestle ropes are attached to two horizontal support rings, which are arranged concentrically around the upper and lower part of the mast or tower, and are electrically combined. Instead of a linear-vertical arrangement, the trestle ropes can also be arranged in a conical shape or with the help of additional bracing or brackets in a bent shape around the supporting mast or tower. If one uses mast or tower-supported fish trap antennas, they act as omnidirectional radiators . By combining fish trap ropes with a separate high frequency feed, it is possible to operate such fish trap antennas as directional radiators . The ARRT antenna is a mast-mounted trap antenna that can be designed as a fading-reducing transmitter antenna . One advantage of the fish trap antennas is that the support tower or mast can be grounded, which makes it easier to use for other radio services , for example in the VHF range, benefits the statics due to the lack of base point isolation and also makes it easier to feed the flight safety lights.
Fish trap antennas have been built in the past decades in different versions for radio transmitters in the long , medium and short wave range . In Germany and Austria, mast or tower-borne fish trap antennas are used on the long-wave transmitter in Zehlendorf , on the medium-wave transmitter in Zehlendorf and Langenberg, and on the short-wave transmitter in Moosbrunn . They were also used on the long-wave transmitter Burg , on the medium-wave transmitters Bremen-Oberneuland (kinked flat trap) and Wolfsheim (as a reserve antenna) and on the short-wave transmitter Rohrdorf (as a reserve antenna) until they were shut down .
See also
literature
- Alois Krischke: Rothammels Antennenbuch . 11th edition. Franckh-Kosmos-Verlags-GmbH, Stuttgart 1995, ISBN 3-440-07018-2 (double cone broadband antenna).
Web links
- Folded unipole antenna in the English language Wikipedia
- LW antenna Zehlendorf 177 kHz
- DWD weather station Pinneberg
Individual evidence
- ↑ a b Bernd Waniewski: SWR Wolfsheim (Rheinsender) - trap antenna . Retrieved February 26, 2013.
- ↑ a b Walter Brummer: Broadcasting station in Bavaria - shortwave transmission system Wertachtal . Retrieved March 2, 2013.
- ↑ a b Walter Brummer: Broadcasting station in Austria - KW broadcasting station Moosbrunn near Vienna . Retrieved March 2, 2013.
- ↑ Bernd Waniewski: Bremen MW Oberneuland . Retrieved March 2, 2013.
- ↑ a b Bernd Waniewski: Langenberg-Rommel MW Diplexer . Retrieved March 2, 2013.
- ↑ Bernd Waniewski: Zehlendorf MW trap antenna and diplexer . Retrieved March 2, 2013.