Holmdel Horn Antenna

This was one of the most important discoveries in physical cosmology since Edwin Hubble demonstrated in the 1920s that the universe was expanding. It provided the evidence that confirmed George Gamow's and Georges Lemaître's "Big Bang" theory of the creation of the universe. This helped change the science of cosmology, the study of the universe's history, from a field for unlimited theoretical speculation into a discipline of direct observation. In 1978 Penzias and Wilson received the Nobel Prize for Physics for their discovery.

• Location — Holmdel Road, Holmdel Township, New Jersey

This type of antenna is called a Hogg or horn-reflector antenna, invented by Alfred C. Beck and Harald T. Friis in 1941. It was built by David C. Hogg. It consists of a flaring metal horn with a curved reflecting surface mounted in its mouth at a 45° angle to the long axis of the horn. The reflector is a segment of a parabolic reflector, so the antenna is a parabolic antenna that is fed off-axis. A Hogg horn combines several characteristics useful for radio astronomy. It is extremely broad-band, has calculable aperture efficiency, and the walls of the horn shield it from radiation coming from angles outside the main beam axis. Therefore, the back and side lobes are so minimal that scarcely any thermal energy is received from the ground. Consequently, it is an ideal radio telescope for accurately measuring low levels of weak background radiation. The antenna has a gain of about 43.3 dBi and a beamwidth of about 1.5° at 2.39 GHz and an aperture efficiency of 76%.

• Illustration — Sign put up on Holmdel Road, urging that the Horn Antenna and its surrounding area be saved • Illustration — On-site plaque commemorating the work of Arthur B. Crawford In 2021, the Crawford Hill site was sold to a developer who was interested in constructing a residential development. This triggered a petition to preserve the property as a park, which preservationists preferred over real estate development. The petition was given to township officials in March 2023, having accumulated over 6,900 signatures. That April, township officials filed a lawsuit in the New Jersey Superior Court to clarify who owned the antenna; the site developer, Crawford Hill Holdings claimed that it owned the antenna and would preserve the property. That June, the town moved to acquire the antenna. In October 2023, the township announced plans to buy and preserve the antenna. The purchase included $5.5 million for 35 acre of land, which would be converted into a public park. The purchase was finalized in January 2024, when the township announced plans for the park. In May 2025, the Institute of Electrical and Electronics Engineers dedicated a plaque commemorating the antenna. In 1992 the receiver and calibration equipment were sent to the Deutsches Museum in Munich, the birth city of Penzias, while the antenna remains in Holmdel, New Jersey. The museum also displays the hardware alongside a functional 1:25 scale model of the horn antenna.