PreamplifierCircuit DCF77


Posted on Feb 5, 2014

DCF77 Preamplifier Circuit DiagramA popular project among microcontroller aficionados is to build a radio-controlled clock. Tiny receiver boards are available, with a pre-adjusted ferrite antenna, that receive and demodulate the DCF77 time signal broadcast from Mainf lingen in Germany. DCF77 has a range of about 1, 000 miles. All the microcontrolle


 PreamplifierCircuit DCF77
Click here to download the full size of the above Circuit.

r need do is decode the signal and output the results on a display. The reception quality achieved by these ready-made boards tends to be proportional to their price. In areas of marginal reception a higher quality receiver is needed, and a small selective preamplifier stage will usually improve the situation further. The original ferrite antenna is desoldered from the receiver module and connected to the input of the preamplifier. This input consists of a source follower (T1) which has very little damping effect on the resonant circuit. A bipolar transistor (T2) provides a gain of around 5 dB. The output signal is coupled to the antenna input of the DCF77 module via a transformer. DCF77 Preamplifier Circuit Diagram The secondary of the transformer, in conjunction with capacitors C4 and C5, forms a resonant circuit which must be adjusted so that it is centered on the carrier frequency. An oscilloscope is needed for this adjustment, and a signal generator, set to generate a 77. 5 kHz sine wave, is also very useful. This signal is fed, at an amplitude of a few milli-volts, into the antenna input. With the oscilloscope connected across C4 and C5 to monitor the signal on the output resonant circuit, trimmer C5 is adjusted until maximum amplitude is observed. It is essential that the transformer used is suitable for constructing a resonant circuit at the carrier frequency. Our proto-type used a FT50-77 core from Amidon on which...




Leave Comment

characters left:

Related Circuits

  • New Circuits

    .

     


    Popular Circuits

    Sealed Lead-Acid Charger
    Strobo triggering schematics
    Wideband radiation monitor
    100Mhz-vhf-crystal-oscillator
    switch mode power supply design of current load sense circuit
    AVR
    Battery charging indicator circuit
    400mA Micropower Synchronous Step-Up DC/DC Converter with Output Disconnect
    Electronic mousetrap power-saving circuit
    Multi-point circuit diagram of a remote control switch
    Detected line current Phase protective circuit 2
    Agricultural harvester warehouse full schematic reminder



    Top