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Large Aperture Loop Antenna ALA100LN

Brand: Wellbrook
Product Code: ALA100LN-1
Price: £150.00
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Large Aperture Active Loop Antenna Model ALA100LN 
UK and European version with psu

New Ultra Low Noise Figure JFET Design


50kHz to 30MHz.

This antenna has recently been upgraded to extend the bandwidth from 10MHz to 30MHz. It is the only active loop antenna to have a noise floor that is lower than the increase in noise due to the amplifier gain.

The Wellbrook Large Aperture Loop ALA100LN is a specialist's antenna designed for the Long wave, NDB Band, Medium wave and Short wave DXer.

The antenna uses a 20m circumference thin wire loop to provide optimum s/n. The ALA100LN uses the similar interference reduction properties as the ALA1530.

The Active Loop Antenna ALA100LN is a large aperture antenna designed to provide improved performance compared to traditional active and passive antennas.

The new ALA100LN is the fourth generation of this antenna and uses 4 high gain low noise JFETs in parallel push-pull, cascode with the proven technique of coupling the FET Gate to the Source with a phase inverting transformer resulting in a much lower amplifier noise floor. This lower amplifier noise floor is achieved by dynamically decreasing the JFET Source resistance from approx. 10 Ohms to less than 1 Ohm.

The noise floor is approx. 7.0dB lower compared to other amplifier types with an equivalent 20m loop inductance.

Product Information - click here for pdf



ACTIVE ANTENNA CONSIDERATIONS

Currently there are several active antennas available providing similar performance.

These active antennas generally fall into two types:

1) Whip and dipoles, responding mainly to the electric field.

2) Loops, responding mainly to the magnetic field

Whip and dipole antennas are more numerous because they easier to design for broadband performance.

The loop antennas are either manually tuned or wideband. The manually tuned antennas can provide excellent results because their selectivity reduces intermodulation products. However, having to manually tune the antenna in step with the receiver is a considerable disadvantage. Thus the broadband loop antenna offer considerable operational advantages. Also it is nearly impossible to obtain a tuned loop antenna that will provide coverage of LW through to SW. In most cases several tuned loops would be required at a considerable cost.

Where active antennas are used in the presence of local interference. The balanced dipole and balanced loop designs provide the best interference rejection. Whip antennas that use the feeder as an RF return path are prone to interference induce on the feeder screen and mains borne noise.

Product Information - click here for pdf

Generally the loop antenna is less sensitive to local interference and static. Also a balanced loop antenna will have a "figure of eight" directivity pattern with deep nulls to further enhance interference reduction.
 

 

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