Wellbrook ALA1530

Wellbrook ALA1530LNP HF Antenna

The ALA1530LNP is the second loop in the IMPERIUM range of the world famous Wellbrook Active Loop ALA1530 long, medium and shortwave antenna.

This Balanced low impedance Magnetic loop has enhanced performance compared to shield and Moebius loop types.
The new JFET design affords a considerable reduction of noise compared to low cost loops using MMIC (Monolithic Microwave Integrated Circuit).

  • shoc can supply Wellbrook worldwide
  • A linear regulated power supply is recommended, because switched power supplies can cause interference!
  • 50kHz-30MHz 1m dia. Aluminium Loop
  • As of April 2021 the amplifier gain has been increased to 28dB
  • Ultra low noise JFET design compared to conventional low noise and MMIC amplifiers
  • Unique two transformer Norton amplifier ensures good performance in a strong signal environment
  • No tuning necessary or matching unit
  • Figure of eight directivity and deep nulls to further reduce interference

The ALA1530LNP has a noise figure of approximately 0.2dB, which give a noise floor that is 13dB lower compared to a similar gain loop with a noise figure of 3dB.
This antenna together with the ALA1530LN are the only 1m dia. loops in production to use an ultra low noise JFET design. The loop has recently had a significant design change to improve LW/MW and SW reception. The antenna gain is increase by 9dB and the LW and MW signal to noise ratio s/n is up to 10dB higher, with an improved s/n on the HF bands. The LW and MW 3rd order IMD is now approx. 20dB lower when compared to the ALA1530 and the ALA1530S+. This being a combination of altering the gain distribution and the lower IMD of the JFETs. The antenna uses 8 very high gain JFETs in parallel push-pull with a Bipolar transistor cascode stage for extended bandwidth. A very low amplifier noise floor is achieved by dynamically decreasing the JFET Source resistance to a fraction of an Ohm. This is achieved using a proven technique developed in the 1980s by coupling the FET Gate to the source with a phase inverting transformer.

A unique 2 transformer push-pull Norton amplifier with a higher HF gain is now fitted in the antenna interface. MW OIP3 has been increased to +55dBm; thus giving this active antenna one of the highest third order intercept points in its class.

The amplifier is now housed in a separate module, thus isolating the electronics from the mechanical stress caused by wind loading on the loop. The amplifier module can be easily replaced in the unlikely event of a failure, without the customer having purchase a new loop antenna with the associated high shipping costs.
A resettable fuse and a power on LED are now fitted to the antenna interface.

The loop antenna responds primarily to the Magnetic Field and rejects locally radiated Electric-Field noise providing far lower noise reception than active whip/dipole antennas. Compared to active whip/dipole antennas, the loop will reduce locally radiated noise by up to 30dB and mains borne noise by up to 60dB. The ALA 1530LNP has 30dB nulls to further reduce interference.
It is ideal for small gardens, indoors and directional reception using an antenna rotator.

Technical data

Feature Data
Frequency range 50 kHz to 30 MHz
Loop Diameter 1 m
Power consumption 12 volts at 500 mA
Amplifier Intercept point typically (MW Band) OIP2 +90dBm, OIP3 +55dBm
Amplifier Noise Figure Approx. 0.2dB
Output impedance 50 ohms BNC
Max. Field strength 400V/m or 1.0A/m pulse