The ultimate guide to antenna construction
Introduction
After passing the amateur radio license exam and being assigned a call sign, the first question that most likely comes to mind is the choice of radio equipment. This is understandable. However, whether shortwave or VHF, it is more obvious and more useful to consider first the local environment and look for realistic antenna possibilities. The expensive high-end transceiver alone is of little use - everything ultimately depends on the best possible antenna.
Now, at the latest, many new questions arise:
- What are my interests and goals?
- How much space do I have available?
- What do I have to consider for the construction?
- How high will the costs be?
- Can I carry out the construction alone...
- ...or do I need additional helpers?
We consider 3 situations
within the scope of possibilities, although there are of course others.
Scenario A. The homeowner who has the ability to put a mast in the backyard, or install a larger antenna system on the house.
Scenario B. The owner or tenant of a floor apartment, who, with often limited antenna possibilities, still wants to achieve something.
Scenario C. The amateur radio operator who wants to participate in portable amateur radio on weekends or for fielddays, SOTA (Summits On The Air) and POTA (Parks On The Air) on vacation.
At first, you should have a rough idea of what you want to achieve. DX hunter, contester or work only occasionally as portable radio operator? Shortwave or VHF? CW, SSB, digital modes, QRO or QRP? Try to judge your possibilities as realistically as possble, but do not give up your dreams!
It should be clear to everyone that with small antennas one needs sometimes a lot of patience, in order to reach certain goals (DX). That excludes some some variants of amateur radio, because EME operation from the balcony would be an impossibility. On the other hand, however, do not let anybody steal your courage! Don't let anybody tell you that something is impossible, unless you spend a lot of money and have huge real estate. Sometimes it just takes more time and creative ideas.
In the following sections, the specific suggestions and recommendations for antenna construction are considered again and again under the aspect of the three scenarios A, B and C mentioned above.
During current economic sitation, most radio amateurs do not own their own house. Many of us live in an apartment. Therefore most readers will probably find themselves in scenarios B and C. Please always pay attention to this marking in the course of the text!
Shortwave
As a radio amateur in scenario A, depending on your budget, more or less everything antenna technology has to offer is open to you. On a large plot of land, it is possible to install fullsize wire antennas for the lower shortwave bands 160 m, as well as 80 m and 40 m. A maximum height is a bit more difficult to realize and requires, if natural guy points like trees are not available, the erection of guyed tubular masts made of steel, aluminum, wood or GRP.
Without suitable guy points for horizontal wire antennas such as dipoles or loops, it is easier to set up vertical antennas using fiberglass telescopic masts for the lowbands. With realistic installation heights of up to 20 m, there must of course still be sufficient space available for the guy wires and the radials. Elevated radials, which are suspended at a relatively low height above the ground, must be resonant, i.e. not shortened. An earth network laid in the ground, consisting of many individual radials of any length, can be adapted to the size of the site. However, as many radials as possible are required for good efficiency. By burying the radials, the actual effort of antenna construction is exceptionally not in the airspace, but on the ground.
For the upper shortwave bands from 30 m to 10 m, a free-standing, rotatable directional antenna with at least two or more elements is the first choice for most radio amateurs. On a smaller property, a lattice tower with directional antenna for the higher HF bands that also serves as a center guy point for one or more wire antennas is the classic choice. Terraced houses and single-family houses on very small plots of land often only allow an antenna mast to be attached directly to the house or a standpipe to be mounted on the roof.
With sufficient stability and steadiness of this standpipe, this construction can carry a not too large KW-Beam and arranged over it, directional antennas for the VHF range and turn by means of rotor. The simplest and most inconspicuous antenna solution is one of the numerous vertical antennas offered, mounted on a short standpipe on the roof. These antennas are available as quarter-wave radiators, as mono-band versions, or as multi-band antennas with blocking circuits and radials. Half-wave radiators have a greater mounting height, but do not require radials that interfere with roof walkability.
Scenario B does mostly exclude the optimal antenna options shown earlier. But also on site of the one or other rental or condominium, especially on the outskirts or in rural areas, there is usually still a garden available. With permission of the landlord or the permission by the owner community, inconspicuous wire antennas for the short wave and VHF antennas on the roof, permit a satisfying participation in the amateur radio. Unfortunately, always depending on the goodwill of the landlord or the owners' association. Whereby the receipt of an antenna permission from the landlord is sometimes easier than by the resolution of an owners' association. In all these cases, it is certainly advisable to voluntarily impose a restriction to e.g. 100 W transmitting power, instead of putting a KW power amplifier into operation and evoking the conflict case.
Indoor antennas for HF
In scenario B, with very little space, what works indoors with a ready-made antenna? Most electric antennas are too long and have very low efficiency when severely shortened. Multiband blocking circuit dipoles suspended under roof often end in disappointment because their length measurements between the blocking circuits are designed for free suspension. The environmental influences under the roof detune the antenna, the propagated resonances are completely elsewhere and the good standing wave ratio is gone.
Correction of the required lengths is extremely complex and difficult for a multiband antenna with blocking circuits. Unshortened monoband dipoles for the upper HF bands, possibly connected in parallel and fed via a common coaxial cable, are a good alternative. With such a combination, 100 DXCC countries and more can be reached with only 5 to 10 W transmit power in telegraphy. In FT8 it is possible with even less power. If there is even less space available, a magnetic antenna, in the room in front of the window, on the balcony or in the attic, is still the best solution.
VHF
Directional antennas for the VHF range 6 m, 4 m, 2 m, 70 cm and 23 cm, from the single very long yagi to the large group of directional antenna, are always possible in scenario A in optimal installation height. Ideally on a separate mast or on a mast tube on the roof of the house. Of course with a rotor, which can carry and turn the whole antenna system. Only a valley location would call these antenna systems into question and set limits.
In Situation B , this applies with the restriction that an antenna permit is available and access with an antenna feed line to the roof is possible. Good for those who live in a condominium or rental apartment on the top floor and can use a balcony or roof terrace. This makes the whole thing easier. A medium sized mast tube with rotor, directional antenna and an omnidirectional antenna placed above it, are then well within the realm of possibility. Furthermore, the broadband Discone antenna, both on the receiving and transmitting side, is well suited for entry-level use.
On the balcony of an apartment below, the possibilities are limited. Simple vertical half-wave radiators, 2-m/70-cm duo-band antennas of the X-series, ground planes as well as vertically mounted, handy directional antennas like the HB9CV or Log-Periodics are suitable in this situation. At best, a 4-element Yagi can be mounted vertically on the balcony railing and, depending on its location, pointed at relay stations a little further away.
For mounting a satellite mirror in the size, as usual for satellite TV, you can almost always find a place. If the free view to the satellite is given, already a short standpipe on the ground is sufficient. Contrary to popular belief, the highest possible location is of course not necessary under this condition. For those who have to put up with modest antenna conditions and a limited radio range, worldwide radio operation via QO-100 is an ideal supplement to local FM operation.
Antenna masts
For large HF Yagis and extensive stacked group antennas, only a lattice mast, at best a heavy tubular mast of larger diameter made from one length, comes into question. Clearly a case for scenario A. Lattice towers are made of galvanized steel or aluminum. Mast structures of this load-bearing capacity require a concrete foundation, structural analysis, and, in most regions, a building permit if the height exceeds 10 meters above ground. Check your local regulations!
Telescopic steel or aluminum masts are guyed, for VHF Yagis and small HF Yagis, equally suitable for users in scenario B and C situations. Fiberglass telescopic masts are predestined for portable applications and carry only light VHF antennas like HB9CVs or LogPeriodics. Furthermore, they are excellent for stationary and portable setup of horizontal and vertical wire antennas.
Antenna Rotors
Especially unrestricted for homeowners in scenario A, more rarely from a floor apartment in an apartment building (scenario B) there is the possibility to use an antenna rotor. Apart from extreme VHF specialists, a rotor is used rather seldom in portable operation (scenario C), in portable use the antenna can also be turned by hand together with the tube mast.
To rotate large HF yagis and extensive, stacked VHF yagis and group antennas, powerful, heavy antenna rotors with a high-quality upper bearing are required. The mechanics must be able to carry the weight of the antenna(s) including the standpipe as well as withstand the lateral forces of the wind load. Only single, small VHF antennas with a few elements on a short boom tube, can be rotated without a top bearing mounted on a short standpipe, using a small and inexpensive rotor.
The guide for antenna construction will be continued! At the end of March/beginning of April we will continue with the topics 'wire antennas, portable operation, legal aspects and do-it-yourself'. The article is rounded off with a list of further websites and books on the subject of antenna construction.
