Antenne filari - antenne dipoli per onda corte
Just a wire? Is that still the way to go?
The wire antenna is the classic amateur radio antenna. This encompasses not only long-wire antennas, but also the classic dipole. This is still the most popular shortwave antenna, whether in amateur radio, for the military, public services or commercial users. A wire antenna dipole is inexpensive, light and - depending on local conditions - can be mounted in many variants. Further, it is unobtrusive, robust and far less affected by bad weather than constructions that are more massive. At the same time, the performance is also easily predictable and far less affected by influences from objects in the vicinity than other types of antennas.
In order not to make the lengths too long or to cover several amateur radio bands at the same time, coils or traps are used. Thus, wire antennas are an excellent solution for many radio amateurs, even when space is limited. Due to the versatile setup possibilities, for example as a Sloper, or as a horizontal or vertical dipole, angled or stretched, there are enough possibilities to set up a wire dipole at almost any location. The desired radiation can also be adjusted by the setup: a low radiation angle is good for long-distance connections; a steep radiation angle is good for local contacts.
In this guide we will show you you how wire antennas are constructed; how they work and which is the right wire antenna for your needs. We also give you some installation and assembly tips so that you can really enjoy your new antenna.
A wire antenna cannot bend or break and offers a minimal wind load.
In the attic, on holiday or on fieldday, guyed from a tree, a mast or the balcony.
True half-wave dipoles, without shortening elements, are hardly realisable as a beam for the long bands - as a wire antenna they are.
The advantages of the wire antenna in different scenarios
So which is the best environment for a wire antenna? Use at home or on the road? Well, you can use it nearly everywhere. Maybe only mobile operation from a car while driving is definitely left out
Home, sweet home
So, at home, it's no problem to set up a large beam, is it?
Not necessarily. In some residential areas, conspicuous antennas are no longer permitted, even outdoor antennas for radio and television are now often prohibited where cable TV is available. And in case when renting an apartment or a flat, you're out of luck anyway. But maybe with a wire antenna, you can be lucky. Whether stretched from a balcony or a tree, it is inconspicuous and causes few problems. If necessary, it can also be installed under the roof in the attic or disguised as a clothesline. The only thing to avoid is interference, so it is better to feed the antenna via coaxial cable with a good choke.
Here, at last, one can draw from the full range of possibilities. But here, too, the farmer from whom you have rented the land with the harvested field might be quite happy if it doesn't look like a NATO manoeuvre, if the police don't have to be alerted by locals and if no heavy vehicles ruin the field. However, even if you can set up a mast with a rotor and beam, a few additional wire antennas are easily attached to this mast. They will allow you to try out additional operating modes, frequencies or directions. In addition, you can finally test-drive everything that too large for the available space at home. Why not build a long wire, full-size dipole also for the lower bands, rhombus antenna, a Lazy Henry and so on. The options are endless with wire antennas. And in case you do not know what to select: Ask us, we will be happy to advise you in choosing the right antenna!
On the road
If you are travelling, whether as a camper or a tourist, every gram less in your luggage and fewer suspicious looks at the border controls or at the security check-in will be welcome. The installation of a wire antenna is easy, even in previously unknown surroundings, with the appropriate aids such as a nylon line for kites or anglers, a fishing rod and casting lead to attach it to a tree. The owner of the campsite or guesthouse will definitely have fewer concerns here than when someone arrives with a truck and a solid mast.
Why buy wire antennas from WiMo?
Admittedly, a wire antenna in particular looks like a thankful object for do-it-yourself construction. For short-term experiments quite conceivable - but not very effective if the traps become unusable after a few months due to the weather. Or if the antenna, which has been painstakingly mounted on a high object, breaks off or even tears through at the first storm. In the end, an antenna made by a specialist is the more efficient option here.
And yes, WiMo is not only a dealer, but also a manufacturer. We manufacture many types of well-known antenna brands, from Kelemen multi-band and mono-band dipoles to EAntenna's wide range of products, to the wellknown Hari antennas and or own ZX Yagi models. In addition, WiMo sells other wire antenna models made by other manufacturers, such as the end-fed "City-Windom" antennas or other manufacturers like Chameleon and Diamond. For limited space we offer multi-band antennas like G5RV, Trap-Dipoles or W3DZZ antennas. We have a huge selection and the expertise to find the right antenna for you.
All WiMo or what?
What are the advantages and features of the different brands?
Kelemen wire antennas are particularly light in construction. This makes them attractive for holidays or less solid suspension points such as a GRP mast. Among other things, they use stranded copper wire instead of steel wire for this purpose. They offer:
• Wide bandwidth
• High efficiency
• Low weight
• Weather and temperature resistance
• 50-ohm feed
In addition to the full-size dipoles, we offer shortened dipoles that can be used in confined spaces. The shortening is achieved by extension coils of Teflon cable inserted into the radiator. However, the greater the shortening, the lower the usable bandwidth - use antenna tuners! Like all Kelemen antennas, the shortened antennas are very light and absolutely weather and temperature resistant.
Siegfried Hari, DK9FN, started to build and sell antennas, baluns and QRP kits for radio amateurs in Seligenstadt in 1977. Thus the company developed into one of the largest European manufacturers of wire antennas. Many radio amateurs also know Siegfried personally from the many flea markets and trade fairs where he attended. His trade sign were in depth technical discussions with him directly at the stand. After 40 years of hard work and at an age of almost 70, OM Hari retired and is happy to enjoy ham radio from his apple orchard in Hungary.
In January 2019, WiMo took over from Siegfried the construction and distribution of Hari antennas under the well-known brand. OM Siegfried would like to take this opportunity to thank his long-standing customers for their trust over the many years and wishes them "good DX" with his products all the time.
The Hari product portfolio
Hari antennas are available in many different versions, covering the whole bandwidth very well. We offer the following types:
• Fullsize Dipoles
• Shortened dipoles
• Multiband Trap dipoles
• Loop antennas
• Zepp dipoles
• Beverage antennas
• Windom dipoles
• G5RV dipoles
• Wire Ground Planes
Rod, EA7JX, has made an name for himself internationally with his antenna manufacturing. In 2018, WiMo acquired the company, further development and manufacturing, with Rod continuing to contribute and bring his experience to the table. Under the EAntenna brand, we carry various designs of wire antennas:
• Shortened monoband dipoles for the 80 or 60 m band.
• Multiband fan dipoles, which consist of several individual dipoles on a common balun. This allows efficient antennas for each band, without losses due to traps.
• Bazooka antennas: Mono-band antennas made from lightweight 75-ohm coaxial cable. They have a particularly high bandwidth, which eliminates the need for an antenna tuner and thus enables high performance.
The range of wire antennas from EAntenna is very wide with the outstanding feature that the baluns are also suitable for very high power. The antennas use plastic-coated, stranded steel wire; the baluns are weatherproofed in an aluminium tube. All other metal components such as clamps and screws are made of stainless steel.
Trap antennas.. what are they?
WHAT NEEDS TO BE CONSIDERED WHEN SETTING UP A WIRE ANTENNA?
The scope of delivery of WiMo wire antennas - regardless of the brand - includes the balun (usually with PL socket), the complete antenna and insulators for the ends.
In addition, you will need guy ropes, the ends of the dipole should be installed about 50 - 100 cm away from the wall or other objects. The rope must be strong enough to withstand the weight of the tightly tensioned dipole, as must the mounting points on the wall of the house, on a mast or a tree.
• one raised suspension point and one on the ground (sloper)
• one raised suspension point and two on the ground (inverted vee)
• two raised suspension points (stretched dipole)
INVERTED VEE.. what are they?
The wall of the house, the gable, a mast or a tree can be used as a raised suspension point.
The dipoles are always made slightly longer than necessary for the lowest band. This gives the user the possibility to tune the antenna to the local conditions (height above ground, ground conductivity etc.). This means that in many cases it will be necessary to shorten the length of the dipole for the lowest frequency band.
Most WiMo wire antennas are available for different power levels, the balun and the traps are the limiting element.
By inserting blocking circuits, traps into the legs of a dipole, further resonances can be created. Trap antennas are usually somewhat shorter than full-size dipoles and offer multiband operation where space does not permit other, larger antennas.
However, the weight of the traps must be taken into account with trap antennas: the blocking circuits, which are usually quite heavy, usually increase the pulling forces considerably: the antenna sags. The loss of average height increases the radiation angle and decreases the efficiency.
Also trap antennas are not wideband antennas: the SWR increases rapidly if you deviate from the resonant frequency, so an antenna tuner may be necessary.
The placement of trap antennas is more critical than for single band antennas. Like any dipole, the antennas should be mounted as high and free as possible to avoid shifting the resonant frequency. Buildings and the like should be as far away as possible. As a reference height for the production of the Kelemen antennas, we assume an antenna height of 10 m.
If the antennas cannot be mounted horizontally for reasons of space, the Inverted Vee suspension is a good alternative: instead of the typical directional effect of a dipole, you then get an almost omnidirectional antenna and only need a central mast. An angle between the legs of 90 to 130° should be aimed for; 75° should not be undercut and the ends of the dipole legs should not be brought all the way to the ground, but extended with some string.
Scope of delivery:
• Complete antenna ready for operation
• Balun with PL socket
• Insulating eggs
Note: The dipoles are always made a little longer than necessary for the lowest band. This gives the user the possibility to adapt the antenna to the local conditions (height above ground, ground conductivity, etc.). This means that in many cases it will be necessary to shorten the length of the Kelemen dipole for the lowest frequency band. Kelemen antennas are available for power ratings from 400 to 2000 watts, depending on the model, see table. All power specifications refer to PEP SSB or CW, where CW means "Morse" and not "continuous wave".
Articoli 1-10 di 42
Articoli 1-10 di 42