Wellbrook Communications

Active ALA 1530+
BROADBAND ACTIVE LOOP ANTENNA
50kHz to 100MHz

BROADBAND ACTIVE LOOP ANTENNA 50kHz to 30Mhz

The ALA1530+ is a compact Active magnetic loop antenna primarily designed to provide improved performance over conventional passive and active antennas. This new loop is the optimised version of the world renowned ALA1530. It is designed to provide much lower intermodulation when used in a high AM Broadcast signal areas.

This Active loop sets new standards for the listener. For the first time it is possible to reject locally radiated and mains borne noise and still provide improved sensitivity compared to larger antennas. 1m dia. Aluminium loop is designed for outdoors, even at ground level. The loop has a frequency range from 50kHz to 100MHz and matches directly to the receiver. The ALA1530+ is probably the only Commercial Active antenna available to the Radio Enthusiast to provide directional reception of the LW/MW bands and the FM Broadcast band.

Photograph of AL1530 Reproduced by kind permision of iBiquity Digital Corp

ALA1530 installed at the SEMA (Auto Show) in Las Vegas
Reproduced by kind permission of iBiquity Digital Corp

The loop can be mounted remotely from the receiver away from local interference. Whereas, traditional antennas require a lot of space and can pick-up local noise.

BROADBAND LOOP FEATURES

Very low intermodulation ensures good performance in a strong signal environment
Up to 30dB rejection of locally radiated noise compared to active whip antenna
Figure of eight directivity and deep nulls to further reduce interference.
Lower noise than indoor tuned loop
Ideal for LW and MW with antenna rotator
Rejects power line noise
Rugged construction, 1m dia. aluminium loop,
supplied with Interface and 12 volt PSU
No tuning necessary or matching unit
No planning problems, works at ground

LOOP ANTENNA ADVANTAGE

The active antenna solves the problem of impedance matching to the feeder and yet the performance is comparable with larger antennas. However, most active antennas are the whip type and respond mainly to the electric-field.

The Broadband Loop responds primarily to the magnetic-field, this ensures high rejection of nearby electric-fields. The intensity of the electric-field is usually higher than the magnetic-field when an antenna is close to interference sources such as TVs florescent lamps, mains wiring etc.

Therefore, by rejecting the electric-field there will be a reduction in local interference compared to other types of active and passive antennas. Interference reduction is further enhanced by the deep nulls of the 'Figure-of-Eight' directivity pattern.

INTERMODULATION

Some active antennas generate intermodulation products which can appear as spurious signals interfering with reception. This interference or second order intermodulation is caused by non-linearity in the amplifier, producing signals which are the usually the sum and difference of strong Broadcast stations. The ALA1530+ Broadband Loop has been specifically designed to reduce intermodulation products to a minimum. The second order and the third order intercept points are typically +75dBm ( IP2 ) and +41dBm ( IP3 ) respectively. Thus the level of the intermodulation products are generally below the atmospheric and man made noise.

ANTENNA DESIGN

The Loop antenna consists of a rigid aluminium loop and a balanced gain optimised broadband amplifier using low noise RF power transistors. The amplifier is encapsulated in resin and housed in a uPVC box, this ensures reliable operation in all weather conditions. The antenna provides low noise performance, large signal handling ability. Rejection of mains borne noise is accomplished by using a balanced amplifier so that the feeder does form part of the antenna return path.

The ALA1530+ is supplied Antenna Interface and a 12 volt regulated power supply. RG58C 50 ohm coaxial feeder cable is recommended for the antenna. The maximum feeder length is 100m. A 1m coax. lead connects the Antenna Interface to the receiver.

The ALA1530+ should be positioned approximately 5m away from any buildings.

TECHNICAL INFORMATION

Power consumption:	12 volts at 160mA
Intermodulation typically: With two signals of 33mV	2nd order -110dB 3rd order -133dB
Intercept point typically:	2nd order +75dBm 3rd order +41dBm
1dB compression point:	+25dBm
Output impedance:	50 ohms, BNC Connector

TYPICAL INSTALLATION

N.B. The Antenna Interface is not used with the ALA 2000

CONCEPTUAL ILLUSTRATION OF THE HIGH ELECTRIC FIELD COMPARED TO
THE MAGNETIC FIELD CLOSE TO A LOCAL INTERFERENCE RADIATOR

N.B. The Loop nulls will also further reduce interference by up to 30dB.
An active whip or dipole antenna will also pick up high levels of interference.

ALA 1530 Calibration Chart .pdf file (fast download)