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Standard repeaters require either the use of two antennas (one each for transmitter and receiver) or a duplexer to isolate the transmit and receive signals over a single antenna. The duplexer is a device which prevents the repeater's high-power transmitter (on the output frequency) from drowning out the users' signal on the repeater receiver ...
A desirable null exists if the transmit antenna is located exactly below the receive antenna beyond a minimum distance. Almost the same isolation as a low-grade duplexer (about −60 decibels) can be accomplished by installing the transmit antenna below, and along the centerline of, the receive antenna.
For example, in the United States, the Telecommunications Act of 1996 allows any homeowner to install "An antenna that is designed to receive local television broadcast signals" but that "masts higher than 12 feet [3.5 m] above the roof-line may be subject to local permitting requirements."
This reflective array television antenna consists of eight "bowtie" dipole driven elements mounted in front of a wire screen reflector. The X-shaped dipoles give it a wide bandwidth to cover both the VHF (174–216 MHz) and UHF (470–700 MHz) bands. It has a gain of 5 dB VHF and 12 dB UHF and an 18 dB front-to-back ratio.
Inherently an antenna diversity scheme requires additional hardware and integration versus a single antenna system but due to the commonality of the signal paths a fair amount of circuitry can be shared. Also with the multiple signals there is a greater processing demand placed on the receiver, which can lead to tighter design requirements.
This mast has two UHF antennas for receiving signals from different directions. The lower antenna is a bowtie array. The upper antenna is a Yagi design. UHF television broadcasting is the use of ultra high frequency (UHF) radio for over-the-air transmission of television signals. UHF frequencies are used for both analog and digital television ...
2.4 GHz helical antenna radiation pattern (NEC simulation) The Numerical Electromagnetics Code, or NEC, is a popular antenna modeling computer program for wire and surface antennas. It was originally written in FORTRAN during the 1970s by Gerald Burke and Andrew Poggio of the Lawrence Livermore National Laboratory. The code was made publicly ...
An antenna array (or array antenna) is a set of multiple connected antennas which work together as a single antenna, to transmit or receive radio waves. [ 1 ] : p.149 [ 2 ] The individual antennas (called elements ) are usually connected to a single receiver or transmitter by feedlines that feed the power to the elements in a specific phase ...