Shure UA874US Active Directional Antenna w/ Gain Switch - 470-698 MHz

The Shure UA874US (UA874 US version) is an active directional UHF antenna that improves wireless microphone reception for Shure receivers and antenna distribution systems from 470 to 698 MHz. A built-in amplifier with four gain settings (+12, +6, 0 and -6 dB) makes up for coaxial cable loss, and its log periodic dipole array aims a 70-degree, 7.5 dBi pickup pattern at the stage while rejecting RF from outside the coverage area.

Compared with a standard 1/2 wave omnidirectional antenna, the UA874 gives greater rejection of signals from outside the area it points at, so it suits remote-mounted receiver antennas aimed at a stage or room. It mounts on a microphone stand with its threaded adapter, or hangs from a ceiling or wall with the swivel adapter bracket. Front LEDs show the selected gain setting and warn of RF overload.

UA874US specifications

Type	Active directional antenna, log periodic dipole array
Frequency range	470 to 698 MHz (UA874US)
Antenna gain	7.5 dBi on axis
Signal gain	Switchable, plus or minus 1 dB: +12 dB and +6 dB (active), 0 dB and -6 dB (passive)
Reception pattern	70 degrees (3 dB beam width)
Third-order intercept point (OIP3)	Greater than 30 dBm
RF overload LED threshold	-5 dBm (active gain settings only)
Connector	BNC, female
Impedance	50 ohms
Power	10 to 15 V DC bias from the coaxial connection, 75 mA
Mounting	Microphone stand thread adapter; ceiling or wall with the swivel adapter bracket
Dimensions (H x W x D)	12.4 x 14.1 x 1.4 in (316 x 359 x 36 mm)
Weight	11.2 oz (317 g)
Operating temperature	0 to 145°F (-18 to 63°C)
Storage temperature	-20 to 165°F (-29 to 74°C)

Does the UA874US need its own power supply?

No. It is powered by 10 to 15 V DC bias sent up the coaxial cable from the receiver or antenna distribution system, and it will not work without that bias, even at the 0 dB and -6 dB settings. Connect it only to equipment whose antenna inputs supply bias.

Which gain setting should I use?

Use the lowest setting that gives good reception, and add only enough gain to cancel the cable loss. Shure's example: a 50 ft cable rated at -12 dB per 100 ft loses 6 dB, so set +6 dB for a total of 0 dB. Extra gain does not add range; it amplifies interference too. The -6 dB setting suits cable runs of 25 ft or less where the transmitter is within 100 ft of the antenna.

What cable should I run to it?

Any 50 ohm low-loss coaxial cable such as RG-8U. Shure's pre-terminated BNC cables include the UA806 (6 ft), UA825 (25 ft), UA850 (50 ft) and UA8100 (100 ft). Avoid sharp bends and kinks in the cable.

Can I use it with in-ear monitor transmitters?

No. The UA874 is a receiving antenna and should not be used for transmitting, such as with PSM transmitters. For in-ear systems, look at the Shure PA805 directional antenna for PSM systems.

How should I place the antennas?

Point each antenna at the coverage area with a clear line of sight to the transmitters, including over the audience, mount antennas at least two feet (one wavelength) apart, and keep them away from metal objects. The antennas and receivers must be from the same band. The UA874 is not for permanent outdoor installations. Always do a walk-around test before a show.

UA874US or UA874WB?

Both are Shure active directional antennas with the same switchable gain. The UA874US covers 470 to 698 MHz, which matches US UHF receivers working in that range. The UA874WB is the wideband version, covering 470 to 900 MHz, for systems with receivers tuned above 698 MHz. The WA874ZP cover fits both.