Fm Transmitter Hunt aka Fox Hunt

      Fox hunt aka fm transmitter hunt is game where the mission is to find the fm transmitters which hidden from the players. The principle used here is the fm transmitters are hidden and they will transmit a melody continuously. The players are provided with fm receivers consisting of Directional ( yagi uda) antennas. By using these directional antennas the locations of the hidden transmitters can be found. There will be more than 4 or 5 transmitters, those who found the maximum number of transmitters will win the competition.

Transmitter section

Description

Here is a simple melody generator circuit you can make using an IC, it is combined with a fm modulator.The  UM66 series are CMOS IC’s  designed for using in calling bell, phone and toys. It has a built in ROM programmed for playing music. The device has very low power consumption.Thanks for the CMOS technology.The melody will be available at pin3 of UM66 and here it is amplified by using Q1 to drive the speaker.Resistor R1 limits the base current of Q1 within the safe values.Capacitor C1 is meant for noise suppression.

       Circuit showing a fm transmitter.Here i have used a bc494 high frequency transistor for making this circuit .The fm modulator is changing the frequency of carrier signal according to the strength of information signal


Component Required

1. Resistor   :39k.100R
2. Capacitor  :10MF,2.2PF,4.7PF-2,102PF,103PF, 0.1uf,
3. Transistor: BC 494, HE8050S
4. Inductor :22nH
5. IC : um66

 Receiver Section

 

Description

                  Circuit showing a fm radio receiver .Here i have used ic cxa1619bs for making this circuit.Construct this circuit on a good pcb and give me your comment. The yagi uda antenna will provide high directivity.Part list and applications are showing below


Part List

Component No:    Value    Usage
R1    220R    Noise Reduction
R2    150R    Crystal Grounding
R3    330R  
R4    330R  
R5    330R,1/2 W      Current Limiting
C1    22pF    Oscillation
C2    22pF    Oscillation
C3    22pF    Oscillation
C4    203pF  
C5    102pF  
C6    4.7MF    Noise Grounding
C7    47pF    Feedback
C8    203pF    Noise Grounding
C9    100MF    Decoupling
C10    4.7pF    Voice Noise Grounding
C11    104pF    Audio Coupling
L1    22nH,3T    Oscillation
L2    22nH,4T    Oscillation
L3    22nH,5T    Oscillation
X1    4.7MHz    IF Frequency Generator
X2    2.7MHz    Mixer Frequency Generator
VC1    27pF Gang    Tuning
U1    CXA1619BS     Main IC

Antenna Design

 FOX HUNT competition in our college