Automatic direction-finding antenna pinpoints rogue transmissions

Now available from Link Microtek is an automatic direction-finding (DF) antenna that allows the source of unauthorised or interfering transmissions to be located rapidly and accurately, even in urban areas where signal reflections can make this a challenging task.

Recent drone activity at Gatwick and Heathrow airports has served to highlight the disruption that can be caused when illicit transmissions continue unchecked, and the new ADFA 1 antenna could be used as part of a solution to help security and communications professionals deal with such situations as quickly as possible.

The device is also suits telecommunication or defence applications.

Manufactured by Narda Safety Test Solutions, the ADFA 1 antenna covers the frequency range 200MHz to 2.7GHz and is designed for use with the company’s SignalShark portable real-time spectrum analyser.

There is no need for a laptop computer. By means of a strong magnetic mount, the antenna can be attached to the roof of any normal vehicle to enable a series of random bearings to be taken in the suspected area.

Each bearing cycle achieves a typical accuracy of 1 degree and takes 1.2 milliseconds, thereby ensuring reliable measurements even for pulsed signals or transmissions of very short duration.

The results can be displayed by SignalShark numerically or with live visualisation of the transmitter location in the form of a heat map. In addition, the ADFA 1 determines the elevation angle of the signal bearing, allowing the location of the source to be narrowed down to an individual floor level.

Users of the new antenna can also observe the broadband spectrum at the same time as determining the signal bearing, which enables them to continue tracking a source that suddenly changes channel.

At the heart of the ADFA 1 is an array of nine antenna elements around an omnidirectional reference element, optimally arranged to achieve reliable measurement results.

The antenna works on the principle of measuring the phase difference between the nine elements and the central reference.

As well as the vehicle mounting kit, there is an optional tripod with quick-release coupling and level indicators, which allows easy set-up of the antenna for DF measurements to trace interference from a semi-fixed location, as is commonly required in military applications.

Housed in a radome measuring 480 (D) x 219 (H) mm, the ADFA 1 antenna weighs 5.6kg and is sealed to IP55 standard to prevent the ingress of moisture and dust.

It has an operating temperature range of -40 to +65 degrees C and when mounted on a vehicle roof can withstand wind speeds of up to 130km/h.

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