ANTENTOP- 01- 2016 # 020

Memorandum on the Beverage Wave Antenna

LIGHTNING PROTECTION

 During some weather conditions such as snow or dust storms, or summer electrical storms, voltages sufficiently high to break down unprotected coupling coil insulation are developed in the antenna system.  To prevent transformer damage from all but direct lightning strikes, L. S. Braasch #270 neon-argon tube arresters or their equivalent with breakdown range of 200 to 300 volts may be connected to the two antenna terminals and ground at both far and near ends of the antenna; also to both terminals of the transmission line from antenna to receivers when the length exceeds two hundred feet.  The ordinary 1-watt I.R.C. metallized resistance units as used at Grand Island for terminal impedances will almost always be found open circuited after each electrical storm occurring in the vicinity of the antennas whether or not protected by arresters.

TRANSMISSION LINES

    Where it is not practical to erect the antenna with the near terminal direct to receiver location, it can be located at any distance up to a half-mile or more from receiver location and the signals brought to the receiver by transmission lines without noticeable loss.  For long stretches the four parallel #14 B & S conductor type of transmission line is preferred.  For distances of 100 feet or less requiring no intermediate supports the two conductors transposed line may be employed.  Two or more transmission lines may be mounted on the same poles or other non-conducting supports when the separation equals or exceeds ten times the spacing of the transmission line conductors.

A coupling transformer with astatic shield is required at the receiver to keep the transmission line balanced and prevent possible pickup of the transmission line getting into the receiver.

When this resistance unit does not itself absorb or reject undesired interfering signals delivered to the receiver while the antenna is in service in the opposite direction, a shilded L.C.R. circuit, Figure 7, also terminated with a short length of lamp cord and a Graybar 3-A plug is inserted in the opposite reception jack of the antenna and by manipulation of C and R the interfering signal can generally be largely or completely erased without reduction in strength of the desired signal, when the interfering signal is more than 90 degree from the direction of maximum reception of the antenna.  It is not as effective for signals predominately sky wave because of their varying phase and intensity.

Some casual experiments and observations in service indicate that by disconnecting and grounding one or the other of the conductors of a two-conductor antenna at the station terminal, the forward reception pattern can be changed sufficiently to permit partial or complete erasure of interfering signals originating thirty or more degrees from either side of the antenna, depending upon which conductor is grounded and without noticeably affecting the strength of the desired signal originating more nearly directly forward or from an angle opposite the grounded conductor.

Rejector circuit

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