ADF or AUTOMATIC DIRECTION FINDER is one of the BASIC navigation machines which works based on the waves at low and medium frequencies. The biggest advantage of these frequencies is having storing GROUND WAVE and can be received over long distances and at low altitudes. ADF main components include: ADF ANTENNA, ADF INDICATOR, and ADF RECEIVER. A brief description about each one has come in below.

ADF ANTENNA: in general, A ADF system works with two LOOP SENSE antennas which different antennas can be used in this section depending on the accuracy required. LOOP antenna, is a dish shape antenna is located under the fuselage and is made of coils and its main function is to detect aircraft direction. SENSE antenna, is a wire-like antenna which is usually located below or on the plane and completes LOOP antenna performance.

ADF INDICATOR: The main ground station which ADF works with is NDB. NDB waves publish in all directions as NONE DIRECTIONAL.

ADF RECEIVER: RADIO PANEL is located at plane which the pilot can adjust his desired ground stations. This device has a RANGE SELECTOR receiver which should be placed in a position where the desired frequency stays on desired RANGE. MAIN SELECTOR button has 5 modes.

Performance theory of the Recipients:

Auto navigation systems, ADF, are a navigation low frequency system. The main part of a radio receiver is included the frequency 190KHZ-1750KHZ and fixed loop antenna. Posted narrowband signal detection is in this frequency range and the detection of the transmitter direction is in the horizontal plane.

According to working the receiver in three different frequency bands, a different capacitor should be parallel in each band with the input antenna to adjust the resonant frequency of the antenna ring. In addition, these electronic devices which mentioned must be changed according in each band. Tuning capacitors and selecting the appropriate circuit for each band embedded in receiver and is controlling by signals which are sending from the user from the controller section. In addition to ADF, the receiver has two working modes, including ANT mode LOOP mode. Users can choice their desired mode from the controller section.

Performance of the proposed sensor system:

As Electromechanical systems of current receiver has reduced system performance in terms of size, weight, maintenance and accuracy of performance, and increases construction costs and  the development of electronic instrumentation compared to the existing systems, the proposal design is based on electronic devices. In addition, due to the advantages of digital implementation in terms of accuracy, cost and ease of manufacturing, processing and detection of mixed signals, the choice of frequencies and the angle transmitter calculating is implemented by the digital transmitter. The signals which were received by orthogonal loop antennas are strengthening at first using RF amplifier using the same lot. As the frequency range of the receiver, there is a possibility of using perfect operational amplifiers for making wave amplifier using the same lot. If necessary, the variable attenuators can be used after amplifiers to compensate probable lot difference in amplifiers. The received signals from Loop antennas enter shown hybrid networks after being amplification. The network is designed so that the input signal is coupled to port A and port C, D signals with equal amplitude and phase difference of 90 degrees. In other words, the signals which coupled to the ports C, D, respectively, must have a zero and 90 degree phase difference. Similarly, signals which have coupled from B input ports to C, D output ports respectively, should have a phase difference of 90 degrees and zero degrees. This hybrid network can be implemented using passive components such as transformers or ActiveX components including operating amplifiers.