ANTENTOP- 01- 2016 # 020

Memorandum on the Beverage Wave Antenna

LENGTH

The conductors are mounted on short, standard cross arms without braces, with the locust insulator pins spaced 16" between centers. This with ordinary

The optimum length for a broadcast band wave antenna is approximately 1800 feet.  This length delivers peak signal strength at closely 550 kilocycles and again at one-half its wave length in meters, or about 1100 kilocycles.  The peaks are, however, rather broad and the signal delivered is considerably stronger than that from a good simple antenna throughout the entire band.  Near the antenna peaks the increase in microvolts to receiver may reach more than 400 percent.

Where space is a consideration, the length can be reduced to 1400 or even 1000 feet, but the signal strength delivery and directivity will be proportionately reduced, and at less than 1000 feet the slight advantage of a wave antenna for the broadcast band over a good simple antenna does not warrant its erection.

telephone line glass insulator gives the desired or adopted 18" spacing of conductors of the finished antenna.

  GROUND

 For maximum efficiency the resistance of the ground system at both the far and near ends of the antenna should approach zero, or at least be less than thirty ohms.  The ground resistance is best determined by the voltmeter-ammeter, alternating current method, but reasonably satisfactory results can be obtained by the use of the battery and voltmeter voltage drop method.

CONDUCTOR HEIGHT

For measurement of a single ground the planted conductors are divided into equal halves and measured, and the result divided by two, or the far

The surge impedance of the wave antenna is determined by its height above the ground, and by soil conditions with regard to moisture, etc.  By erecting the conductors at a minimum of ten feet above the ground, the surge impedance remains more nearly constant during all seasons than when erected at a lower height.  If erected at a height greater than fifteen feet the pickup of the vertical leads at the far and near terminals may considerably reduce directive properties.  If a greater height is required at gates or other passages, the higher poles should be erected at the sides of the opening and the conductors brought down vertically, proceeding at the selected height after the high point has been bridged.  Reasonably uniform height of the conductors throughout their length is, of course, preferable.

and near terminal resistances measured through the antenna conductors for the combined resistance of the two terminals or the series resistance of the entire system.

If the voltage drop method of measurement is used and should polarization or other direct current effects produce absurd readings such as negative resistance, a resistance of 100 ohms or more may be placed in series with the circuit and two measurements taken with changed polarity.  The average of the two recorded values divided by two in the case of a divided system, less the added external resistance may then be considered a reasonable approach to the actual resistance.  Due to polarization, readings of instruments should be taken at the moment of contact.

POLE ERECTION

The standard practice of telephone line construction is followed.  The poles should be spaced approximately one hundred feet apart and for mechanical strength the conductors should be #12 B & S hard drawn copper.  The line should generally follow the earth's contour, but small knolls are disregarded and the tops of the poles after planted may be trimmed for general or even gradient of the conductors.

For single, unidirectional reception or single conductor antennas, the conductor can be mounted on ordinary pole brackets attached to the poles.

For unidirectional reception from front or rear, or both, the two-conductor type of construction is required. 

If difficulty is experienced in obtaining proper ground resistance values, the constructor is referred to U. S. Bureau of Standards' Technological Paper #108, issued June 20, 1918.

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