Editing Log-periodic antenna (section)

== Short wave broadcast antennas ==
{{multiple image
| align = right
| direction = horizontal
| header   =
| image1   = Moosbrunn drehbare logarithmisch-periodische Antenne (2).JPG
| caption1 = Wire log-periodic transmitting antenna at international shortwave broadcasting station, Moosbrunn, Austria. Covers 6.1&ndash;23&nbsp;MHz.
| width1   = 288
| image2   = LPA_antenna_suitable_for_short_wave_broadcast.png
| caption2 = Diagram of a zig-zag shortwave LPA antenna. Black shows metallic conductors; red shows insulating supports.
| width2   = 180
}}

The log-periodic is commonly used as a transmitting antenna in high power [[International broadcasting|shortwave broadcasting]]<ref>{{Cite web|url=https://www.antenna.be/art1.html|title=Antennas for the Shortwave Broadcaster|website=www.antenna.be}}</ref> stations because its broad bandwidth allows a single antenna to transmit on frequencies in multiple [[Shortwave bands#International broadcast bands|bands]]. The log-periodic zig-zag design with up to 16 sections has been used. These large antennas are typically designed to cover 6 to 26&nbsp;MHz but even larger ones have been built which operate as low as 2&nbsp;MHz. Power ratings are available up to 500&nbsp;kW. Instead of the elements being driven in parallel, attached to a central transmission line, the elements are driven in series, adjacent elements connected at the outer edges. The antenna shown here would have about 14&nbsp;dBi [[antenna gain|gain]]. An [[antenna array]] consisting of two such antennas, one above the other and driven in phase has a gain of up to 17&nbsp;dBi. Being log-periodic, the antenna's main characteristics ([[radiation pattern]], gain, [[driving point impedance]]) are almost constant over its entire frequency range, with the match to a 300&nbsp;Ω feed line achieving a [[standing wave ratio]] of better than 2:1 over that range.