ANTENTOP- 01- 2016 # 020

Memorandum on the Beverage Wave Antenna

    This seemingly unreasonable circuit connection is, apparently, more effective during afternoon hours or for several hours before local sunset.  It is frequently not effective at all.

    In some instances forward interfering strong signals can be more completely balanced out by connecting a simple or general purpose antenna to one of the terminals of the signal rejector for clear reception of weak signals on the same frequency originating in the rear.

    In order to obtain a better balance at the far end, and to partially or completely eliminate pickup by the vertical ground lead at both far and near terminals, a Beverage reflection transformer, Tr, Figure 6, is employed and a lead covered #12 B & S conductor used as a shielded vertical ground connection.  The conductor with lead shield is made water tight at the bottom by soldering conductor and shield together and connecting the whole to the underground radials.  The transformer housing is grounded to the upper end of the lead shielding and the coil terminal to the shielded conductor. 

This arrangement is an apparent improvement in directivity over the exposed, directly grounded, vertical section of the antenna conductor.

TEST FOR TRANSMISSION LINE BALANCE

The transmission line may be checked for signal pickup or unbalance by disconnecting the two antenna wires and connecting a resistance across the transformer in place of the antenna and equal to the surge impedance of the two antenna conductors.  Very little pickup of signal or noise should register in the receiver from a well-balanced line.

TEST FOR TRANSFORMER BALANCE

The center-tapped coupling transformers may be tested for balance by the use of a signal generator and receiver connected as shown in Figure 8.  When properly balanced the receiver will indicate nearly zero input or a very small transfer of energy to the secondary of the transformer.

Circuit for Testing Transformer Balance

TERMINATIONS

    Impedances Ra and Rb in Figure 6 should be equal to the surge impedance of the transmission line as calculated from:

(s equals spacing from center of wires)
(d equals diameter of wire [d and s in same units])

The transformer Ta couples the transmission line to the

two-conductor antenna and the two wires are now acting only as transmission line to carry the reflected signal from A direction to the receiver. The impedance of the two-conductor antenna serving as a transmission line is calculated from the same formula. The Grand Island transmission lines are approximately 400 ohms and the antenna conductors 700 ohms.

The transformer Tb couples the transmission line to the antenna with the two wires acting as if they were in parallel, because the primary of Ta has

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