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Can you please explain the working of modern electric ADF recievers

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    $\begingroup$ Have you seen this excellent answer on how ADF antennas work? $\endgroup$
    – Bianfable
    Dec 5 '21 at 11:32
  • $\begingroup$ @Bianfable i've seen this. this does not explain the working of the electric adf receiver as well. i want to know how it processes the signals $\endgroup$ Dec 5 '21 at 13:15
  • $\begingroup$ @mins what i'm really trying to ask is that when the ADF receives the signal, how would the ADF components process this signal electrically to find NULL - Since there is NO antennae that is able to Rotate physically in space? $\endgroup$ Dec 5 '21 at 14:37
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    $\begingroup$ At some point a question crosses the threshold from aviation to electrical engineering theory. If the first linked question doesn’t explain the working of an ADF well enough then we are knocking on that door…. (What are you looking for, a functional breakdown of components on the circuit board?!) $\endgroup$ Dec 5 '21 at 17:21
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A modern ADF antenna is made either of 4 individual antennas or off two crossed loops.

ADF antenna, 4 elements

ADF array, source

The signal strength is the same on all elements, however the distance between elements introduces a delay, which translates into a phase difference on antennas.

The principle is based on comparing the phase on two diametrically opposite elements (or in a loop).

With 2 pairs the system is able to determine the U and V amplitudes of a vector. By combining U and V it is possible to determine the direction of arrival. The accuracy is a few degrees, depending on the size of the array.

Sensing the phase difference

Sensing the phase difference (the dark green sine is the phase of the top-left element

This principle is not new, but is now very simple due to modern comparison techniques. It is known as Watson-Watt direction finder:

enter image description here

Original Watson-Watt direction finder using a Lissajous pattern, source

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