“Log Periodic Antennas” is the topic of the current (January 3) episode of the “ARRL The Doctor is In” podcast. Listen…and learn!
A log-periodic antenna , also known as a log-periodic array or log-periodic aerial, isa multi-element, directional antenna designed to operate over a wide band of frequencies. It was invented by Dwight Isbell and Raymond DuHamel at the University of Illinois in 1958.
The most common form of log-periodic antenna is the log-periodic dipole array or LPDA, The LPDA consists of a number of half-wave dipole driven elements of gradually increasing length, each consisting of a pair of metal rods. The dipoles are mounted close together in a line, connected in parallel to the feedline with alternating phase. Electrically, it simulates a series of two or three-element Yagi antennas connected together, each set tuned to a different frequency.