WIRE ANTENNAS – Aerial Designs with NEW Advanced mathematical constructs miles Ahead of the Competition in transmit.
WIRE ANTENNAS – Aerial Designs with NEW Innovative mathematical constructs miles Ahead of the Competition in transmit.
Aerial/Antenna Designs with NEW Innovative mathematical constructs miles Ahead of the Competition in transmit.
A wire antenna is a radio antenna consisting of a long wire suspended above the ground, whose length does not bear a particular relation to the wavelength of the radio waves used, but is typically chosen more for convenience of CB Radio. The wire anyenna may be straight or it may be strung back and forth between trees or walls just to get enough wire into the air. Due to the great variability of the (unplanned) CB antenna structure, effectiveness can vary wildly from one installation to another. Wire CB antennas are typically fed at one end against a suitable counterpoise (such as earth ground).
They are widely used as receiving antennas on the long wave, medium wave, short wave bands, as well as CB transmitting antennas and on these HAM bands for small outdoor, temporary or emergency transmitting stations, as well as in situations where more permanent beam antennas cannot be installed.
1 Wire and long wire antennas 2 Radiation pattern 3 Construction 4 References
Wire and Long Wire Antennas
Often random wire antennas are also (inaccurately) referred to as long-wire antenna. Actual long-wire require a length greater than a quarter-wavelength (λ/4) or half (λ/2) of the radio waves (most consider a true long wire to be least one wavelength), whereas CB random wire antennas have no such constraint.
When the length of the wire is near an even multiple of quarter-wavelengths, its feedpoint impedance may take on extreme values (thousands of ohms) due to resonance, which can cause low CB Radio efficiency with popular impedance matching schemes.
The radiation efficiency of the wire antenna is not affected; if the CB antenna is worked against a restrictive counterpoise (such as a poor ground) and a suitable matching scheme is used, the efficiency of the wire antenna system may actually increase significantly. For the amateur radio HF bands wire antenna, use a table of odd multiple lengths, and then down-selected these to pick an ideal work-any-band length of 74 feet (22.56 m).
CB Wire Aerial/Antenna Radiation Pattern
The radiation pattern of a new thin wire CB antenna is easily predictable using aerial modeling. For a straight wire, the radiation pattern can be described by axially symmetric multi-pole moments with no component along the along the CB wire direction; as the length of the wire is increased, higher multi-pole contributions become more prominent and CB multi-pole lobes (maxima) at angles to the RF antenna axis develop.
Under about 0.6λ a wire CB antenna will have a single lobe with a maximum at right angles to the axis. Above this the lobe will split into two conical lobes with their maximum directed at equal angles to the wire, and a null between them. This results in four azimuth angles at which the gain is maximum. As the length of wire in wavelengths increases, the number of lobes increases and the maxima become increasingly sharp.
Any unpredictability of the radiation pattern is caused by uncontrolled interaction with nearby matter (such as soil or structures). For example, a long wire cb antenna close to the ground will form a leaky two-conductor radio transmission line and therefore also act somewhat as a traveling radio wave antenna, with reception off the end of the wire (the system is no longer axially symmetric). A new folded or zig-zag antenna may exhibit a more complex pattern as there are even fewer symmetry constraints on the CB dipole moments that may contribute. Long wire antennas are reported to be more effective for radio reception than multi-element beam antennas such as Yagi or quad antennas with the same length of wire.
Wire Antenna Construction
A typical permanent wire CB antenna strung between two buildings. This example has a lightning switch to ground the Ham Antenna for safety during electrical storms.
A wire CB antenna usually consists of a long (at least one quarter wavelength) wire with one end connected to the radio and the other in free space, arranged in any way most convenient for the space available. Ideally, it is a straight wire strung as high as possible between trees or buildings, the ends insulated from supports with strain insulators. Typically it is made from number 12 or 14 AWG (1.6 to 2.0 mm (0.063 to 0.079 in) diameter) copper-clad wire. Folding the wire into a zigzag pattern to fit in a limited space such as an apartment or attic will reduce effectiveness and make theoretical analysis extremely difficult. (The added length helps more than the folding typically hurts.)
If used for transmitting, a random wire antenna usually will also require an new amateur antenna tuner, as it has an unpredictable impedance that varies with frequency. One side of the output of the tuner is connected directly to a wire antenna, without a transmission line, the other to a good earth ground. A quarter-wavelength sized wire works best, and unless fed through a half-wavelength will exceed the matching ability of most tuners.
Even without a good earth, a wire antenna will also radiate, but it will do so by coupling to any nearby conducting material; this is not recommended. The ground for a wire antenna for CB Radio may be chosen by experimentation. Radio grounds could be returned to a nearby cold water pipe or a wire approximately one-quarter wavelength long, or can be replaced by randomly laid-out quarter-wavelength counterpoise wires attached to the ground connection.
Straw, R. Dean (2003). The ARRL Antenna Book, 20th Edition. Newington, Connecticut, USA: The ARRL, Inc. p. 944. ISBN 0-87259-904-3.
Practical Antenna Handbook (Carr, Mc Graw Hill) – Chapter 9
The ARRL General Class License Manual, 6th Ed. USA: American Radio Relay League. p. 6.6. ISBN 978-0872599963.
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