ETS-Lindgren 3147 Log Periodic Dipole Array Antenna - Manual (Page 28)

Front-to-Back Ratio for Model 3147
The front-to-back ratio is representative of how well the antenna
propagates energy in the end fire direction. The measurement is made
by first positioning two identical Model 3147 antennas face-to-face at a
2-meter height and a 3-meter distance. A signal is transmitted through
one antenna and received with the other. The transmitting antenna is
then rotated 180° in azimuth so that the back is pointed towards the
receiving antenna. The difference between the two measurements is
taken as the front-to-back ratio.
28 | Typical Data