High VHF Log Periodic Antenna for 174-230 MHz
Model: PA31-LPA10 - 10 Element Log Periodic Antenna
The PA31-LPA10 log periodic antenna is a horizontally polarized 10 element antenna covering the high VHF band from 174-216 MHz. The antenna is broad band from 174-216 MHz, thus it is able to accomodate multiple high VHF input channels at the same time. The PA31-LPA10 is composed of stainless steel and features cantilever mounts at the rear of the antenna. The antenna is manufactured complete and shipped fully assembled, therefore no on-site assembly is required.
The antenna can be custom tuned for a VSWR of less than 1.10:1 across multiple channels in the high VHF band, as the log periodic antenna by nature is a very broad band antenna design. In addition, log periodic antennas have a very high front-to-back ratio, exceeding 20 dB and approaching 30 dB for mult-element arrays. The addition of multiple antennas stacked both vertically (one on top of another) and horizontally (multiple log periodics oriented around the tower) increase coverage and gain of the array.
Log Periodic antennas that are multi-element are considered phased arrays. The elements are positioned in-phase in the forward lobe so that each additional element reinforces and adds forward gain and directivity in the direction the log periodic is oriented. Likewise and in so doing, the elements are out of phase to the rear, or behind the antenna, where each additional element reduces gain to the rear. Since the elements are out of phase to the rear, the log periodic antenna has a high ratio of signal in the forward lobe as compared to rear lobe, called high "front-to-back ratio". If protection to the rear is required at a particular site, either from a co-channel or adjacent channel carrier, the log periodic is probably the best antenna choice at providing phased isolation to the rear by virtue of the design of the log periodic antenna.