the other direction, from the receiver end of the wire, induce currents propagating toward the terminated end, where they are absorbed by the terminating resistor. Gain While Beverage antennas have excellent directivity, because they are close to lossy Earth, they do not produce absolute gain; their gain is typically from −20 to −10 dBi. This is rarely a problem, because the antenna is used at frequencies where there are high levels of atmospheric radio noise. At these frequencies the atmospheric noise, and not receiver noise, determines the signal-to-noise ratio, so an inefficient antenna can be used. The weak signal from the antenna can be amplified in the receiver without introducing significant noise. The antenna is not used as a transmitting antenna since, to do so, would mean a large portion of the drive power is wasted in the terminating resistor Directivity increases with the length of the antenna. While directivity begins to develop at a length of only 0.25 wavelength, directivity becomes more significant at one wavelength and improves steadily until the antenna reaches a length of about two wavelengths. In Beverages longer than two wavelengths, directivity does not increase because the currents in the antenna cannot remain in phase with the radio wave. Implementation A single-wire Beverage antenna is typically a single straight copper wire, between one-half and two wavelengths long, run parallel to the Earth's surface in the direction of the desired signal. The wire is suspended by insulated supports above the ground. A non-inductive resistor approximately equal to the characteristic impedance of the wire, about 400 to 600 Ω, is connected from the far end of the wire to a ground rod. The other end of the wire is connected to the feedline to the receiver. A dual-wire variant is sometimes utilized for rearward null steering or for bidirectional switching. The antenna can also be implemented as an array of 2 to 128 or more elements in broadside, endfire, and staggered configurations, offering significantly improved directivity otherwise very difficult to attain at these frequencies. A four-element broadside/staggered Beverage array was used by AT&T at their longwave telephone receiver site in Houlton, Maine. Very large phased Beverage arrays of 64 elements or more have been implemented for receiving antennas for over-the-horizon radar systems. The driving impedance of the antenna is equal to the characteristic impedance of the wire with respect to ground, somewhere between 400 and 800 Ω,