The Beverage Antenna
The testing was done on very low frequencies, from 12 to 50 kHz and later on in the medium frequency range from 200 kHz to 1.5 MHz. Normally, the Beverage antenna is not used above 3 MHz or in the higher end of the short wave frequency spectrum. It is described as a non-resonant antenna and is terminated at the far end with a noninductive resistive termination of around 500 ohms going to a ground rod.
The antenna is usually two or more wavelengths long with one or more wire elements hooked in parallel. The use of more than one wire reduces the characteristic impedance of the antenna and allows the termination resistor to be of a lower value. Antenna impedance is fairly constant over a wide range of frequencies and the antenna will retain its electrical characteristics over a wide range.
Wave Tilt
The Beverage antenna operates on a principle known as wave lilt. Wave tilt occurs where a vertically polarized wave travels over the imperfectly conducting surface of the earth. Due to the slower propagation constant of the earth’s surface, the part of the radio signal that is in contact with the earth slows down, giving the lower portion of the wave a tilt. The amount of tilt depends on the frequency and characteristics of the surface over which the wave is traveling. As the surface conductivity decreases, the propagation of the wave at the surface decreases and the angle of the tilt increases.
Works Best in Dry Soils
As a consequence, the Beverage antenna works best over soil with poor conductivity, such as desert sands and rocky soil. Salt marshes and sea water have very high conductivity and the effectiveness of the antenna is reduced as almost no tilt occurs. This type of antenna receives a vertically polarized ground wave signal more efficiently than a horizontally polarized signal. It responds well to the arrival of skywaves since there is a tilt to the down-coming wave. The magnitude of the induced voltage will depend on the angle of the incoming wave in relation to the axis of the antenna. The closer a skywave, or any other incoming signal is to the axis of the Beverage, the greater the amount of signal induced to the antenna.
Terminator Factor
The directional effects of the Beverage antenna are created by the terminating resistor at the far end of the antenna and its length. As a signal contacts the antenna at the terminated end and travels toward the transmission line and the receiver, the signal is not attenuated by the termination resistance since the current generated by the signal in the antenna is travelling away from the termination. However, a signal coming from the receiver end of the antenna travels down the antenna and is absorbed by the terminating resistor.
Also any signal not completely dissipated in the receiver and bounces back down the antenna, is also absorbed. This eliminates any SWR that would normally exist on the antenna. The antenna pattern is along the direction of the antenna and gets narrower and shows higher gain as the antenna gets longer. Antenna height needs to be no higher than 15 feet (4.6m) as there is little gain in efficiency to be realized above 15 feet.
Mainly for Reception
For the most part, the Beverage antenna is used for receiving, but it can be used for transmitting if it is so constructed. The termination resistor or resistors must be able to handle half of the transmitter power and the antenna has to be put up with transmitting type insulators. The signal radiated from a transmitting Beverage can be called elliptically polarized since it contains both horizontal and vertical components of wave travel. At any distance however, the signal is predominately vertical as a result of normal ground wave propagation.
Feeding
The normal method of feeding a Beverage is with an unbalanced non-resonant transmission line. Since the transmission line in use today is nowhere near the 500 Ω+ of the impedance of a Beverage, a step-up transformer is needed to match things. Other methods of coupling to the antenna have been employed including antenna matching networks and even stub matching systems. Most amateurs use small transformers to match the receiver and coax impedance to the antenna.
180 Meter Band
As far as amateur use is concerned, the Beverage is usually confined to the 160 meter band as the ground wave on 160 is so extensive. On the higher frequencies, the presence of the skywave tends to restrict the efficiency of the Beverage antenna.
Good on Marine Band
The Beverage was very productive on the marine frequencies in the 2 to 3 MHz range at a commercial site on the Texas Gulf Coast. The five antennas covered an area from the east-northeast to the south with the antennas fairly evenly distributed along the compass points. The system was installed in the latter part of October, 1988 and signals could be heard from ships off of the coast of Venezuela on 2.182 kHz at 4:00pm local time. U.S. Coast Guard stations could be heard as far away as North Carolina at the same time of the afternoon just by switching antennas.
The longest antennas were 600 feet long and were the ones aimed NNE and SSE. The next two were 450 feet long and were aimed NE and SE. The remaining antenna was only 300 feet long and was aimed due East. The antennas were supported at the receiver end by a 15-foot (4.6m) high cedar post and sloped down to about four feet from the ground at the far end. Small impedance matching transformers were used to match the RG-58A/U to each antenna.
Works Well in Storms
Results were excellent and the Beverages performed consistently well during the remainder of the time the station was on the air. The customary evening thunderstorms that form inland with considerable lightning could not be heard on the three inner antennas and only faintly on the longest ones. Prior to the installation of the Beverages, all communications were completely wiped out when the storms started up. Traffic between ships several hundred miles out in the Gulf of Mexico were handled with no problems. Q5 phone patches were the order of the day, instead of the ships having to get within 120 miles of the station in the day. Night operations were not troubled with any interference from inland storms or signals from the West Coast and North Pacific Coast that had usually plagued the station in the past.
Replaced a 350ft Vertical
The antenna replaced by the Beverages was a 350 foot tall vertical that picked up everything equally well. However, a 50 kW a-m broadcast station would cause the receiver multi-coupler to overload occasionally with a resulting loss of signal on the marine frequencies. Any lightning storm within 1000 miles would disrupt communications. Inter-mod from be stations would cause problems in general and thus, maintaining a communications circuit was extremely difficult, if not impossible most of the time. The installation of the Beverage array stopped all of the problems instantly. Night time communications were enhanced and the range was extended greatly. The Beverage antennas were quiet and the normal atmospheric noise was greatly subdued.
Good Reports
W5JXP has been using several Beverages for some time and reports the only problem was that the 1000-foot (305m) Beverage was too directional. The shorter ones were better for amateur usage since they are not as directional and allowed stations to be heard that were not quite on axis with the antenna.
Broad Range of Receiving
In general, the Beverage antenna will do what it is supposed to do if you have enough real estate to put up one. For the frequency ranges from VLF to about 3 MHz, the Beverage is an exceptionally good antenna. It will allow receiving broadcast stations in the 550 kHz to 1.600 MHz range in areas of poor ground with a good signal being presented to the receiver input. The atmospheric noise level is lower on a Beverage than any other kind of long wire antenna and tall supports are not needed.
Originally posted on the AntennaX Online Magazine by Richard Morrow, K5CNF
Last Updated : 19th March 2024