HF Antennas For All Locationspdf ((LINK))
A thought-provoking book which has been a major contribution to the state of the art from an acknowledged expert. It explains the 'why' as well as the 'how' of HF antennas, and takes a critical look at existing designs in the light of the latest developments.This second edition has been completely revised and greatly expanded. There are more novel antanna designs, including beams which cover more bands with fewer problems, no trap losses and better rejection of interference. A new chapter presents a comprehensive review of ways to make antennas smaller, with particular emphasis on small transmitting loops.An essential reference for the experimenter and enthusiast.2nd Edn, 1993, RSGB, paperback, 187 by 245 mm, 322 pages, ISBN: 1-872309-15-1.
HF Antennas For All Locationspdf
The smallest and second most efficient antenna is the magnetic Alpha Loop. It requires you to turn a knob on the antenna to tune when changing bands. These first two antennas are very effective for even low power operations. This is because they have a higher efficiency Q rating. Having a higher Q rating means an antenna has a narrower bandwidth.
The third most efficient antennas are the MIL 2.0 and the FMJ. These provide hands-free operation enabling you to just touch the button on your tuner when changing bands. Alternatively, you may choose to use one of our EFHW dipole antennas. Just keep in mind if you do, that they will have a Signal Pattern similar to half of a dipole.
Some operators get two antennas; one for DX and one for NVIS. Other operators get one antenna, which can be deployed to either enhance DX or NVIS characteristics. We hope that you feel armed when taking what the band-conditions hand you. Take charge of those solar cycles and choose one of the following Alpha Antenna systems that meets your operating objectives. To understand more about band conditions and solar cycles CLICK HERE.
A thought-provoking book which has been a major contribution to the state of the art from and acknowledged expert. It explains the 'why' as well as the 'how' of HF antennas and takes a critical look at existing designs in the light of the latest developments.
The Moxon antenna is popular with amateur radio enthusiasts for its simplicity of construction. The drawing shows the system of construction. The driven element is at the left, and the parasitic on the right, mechanically connected with an insulator (blue in the drawing). The antenna is in layout similar to the well known VK2ABQ-Square. For use on shortwave-bands spreaders are commonly made of bamboo or glass-fiber reinforced plastics, carrying a radiator and reflector made from wire. Such antennas can be built with little wind load and minimal weight.
L.B. Cebik (W4RNL) made detailed comparisons and calculations of several different versions of Moxon antennas. AC6LA provides a calculator which is based on empirical formulas developed by Cebik.
Modern antennas come in many different shapes and sizes. Each antenna is formed by its function. Often, a well-equipped airplane will have an antenna farm on the belly, and it can be confusing to try to figure out what each antenna does. But taken one by one, those antennas are easier to understand. The frequencies at which they operate and their directional qualities usually determine their shape and placement.
Communication antennas are basic in operation. Each com transmitter has its own antenna, mostly for redundancy. They can be mounted on either the top or bottom of the aircraft, but each installation is susceptible to shadowing from the fuselage. Shadowing is caused by structure, such as the vertical stabilizer or landing gear doors, in the transmitting path of the antenna. Know where your antennas are and how shadowing may affect their range and coverage.
The VHF nav antenna is almost always mounted on the vertical tail, and there are three types: the cat whisker, the dual blade, and the towel bar. The cat whisker consists of a couple of rods jutting out from each side of the vertical stabilizer at a 45-degree angle. But the cat whisker antenna is poor at receiving signals from the side. The dual blade is just that, two blades, one on each side of the tail. The towel bar resembles the common bathroom fixture, one on each side of the tail. The blade and towel bar antennas have equal receiving sensitivity from all directions. A single nav antenna almost always feeds mulitple nav receivers and sometimes the glideslope as well. Therefore, a failure in the nav antenna system would cause multiple systems to malfunction.
Communications radios can cause a lot of interference with GPS, because of the proximity of the panel units or their antennas. Therefore, it is important that the com and GPS antennas be mounted as far apart as possible. Sometimes a com antenna must be relocated to the bottom of the aircraft.
Marker beacon signals are highly directional, which means you have to be almost directly over the transmitting ground station to receive them; therefore, marker beacon antennas need to be on the bottom of the aircraft. There are a few different types of marker antennas; the more common types look like little canoes about 10 inches long. For some installations, Cessna has used flush antennas that appear to be flat plates under the empennage. It also has used an antenna that consists of a thick wire that protrudes straight down out of the empennage and then makes a turn toward the tail.
Real estate is very scarce on an aircraft, and sometimes there is very little left for antennas. Every antenna location is a compromise between a solid mounting, shadowing, other antenna interference, ground planes, and aerodynamics.