English: A UHFtelevision antenna from 1952. It is a rhombic antenna, a directional antenna which has the broad bandwidth to cover the US UHF band of 470 to 890 MHz. The rhombic is a nonresonant traveling wave antenna so the length of the elements is not critical, each of the 4 sides is several UHF wavelengths long. The antenna is composed of two wires which are connected at the near end (upper left) with a resistor equal to the characteristic impedance of 470 - 500 ohms, and at the far end to the 300 ohm Twin lead feedline to the TV. The beam pattern is unidirectional off the near end. It has gain of 5 dB at low end of the band rising to 10 dB.at the high end.
This 1952 issue of Radio and Television News magazine would have the copyright renewed in 1980. Online page scans of the Catalog of Copyright Entries, published by the US Copyright Office can be found here. [1] Search of the Renewals for Periodicals for 1978 and later show no renewal entries for Radio and Television News. Therefore the copyright was not renewed and it is in the public domain.
Note that it may still be copyrighted in jurisdictions that do not apply the rule of the shorter term for US works (depending on the date of the author's death), such as Canada (70 years p.m.a.), Mainland China (50 years p.m.a., not Hong Kong or Macao), Germany (70 years p.m.a.), Mexico (100 years p.m.a.), Switzerland (70 years p.m.a.), and other countries with individual treaties.