signal builds up until it reaches B where the phase is reversed
by grounding one of the conductors and leaving the other free
after which it is reflected back to T using the antenna conductors
as an untransposed transmission line.
The signals from B direction are dissipated either completely
or partially in impedance R connected from the center tap of T
to ground. It will be noted that Figures 2 and 3 are the same except with respect
to far and near terminal connections. When it is changed
as shown, the antenna can be made unidirectional for either forward
or rear reception, but not for both forward and rear reception
the wave length of the signal to be rejected is a multiple of
one-half wave of the length of the antenna, it is either completely
or largely absorbed in resistances Rb
multiple frequencies of one-quarter wave length of the antenna
length deliver a greater residual or undesired signal to the receiver.
In order to balance
out an undesired signal originating at an angle of more than ninety
degrees from the source of a desired signal originating in direction
of maximum reception of the antenna, part of the undesired signal
is reflected back to T in proper phase and magnitude to cancel
itself out. This is accomplished by the insertion of a tuned
circuit in series with a variable resistor at the far terminal,
as in Figure 4 for rear signal rejection, and as in Figure 5 for forward signal rejection.