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1977 DOD 250

February 05, 2017

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Layout & PCB Transfer

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How to Build a Fox Hunt Transmitter

It is a very Simple Build a Fox Hunt Transmitter. This 2 meter 144 MHz fox hunt transmitter is used in amateur competitions where a hidden transmitter is to be “hunted” using mostly home brewed receivers and antennas. The foxhunt electronic circuit is the transmitter. It radiates a high quality signal without unwanted harmonics. Transistor T1 and the crystal together make the oscillator that generates a 36MHz signal. The unwanted 12MHz basic frequency of the oscillator is suppressed by the filter circuit made of L1, C3, C2. The L2/C4 circuit is set to the fourth harmonic or 144 MHz. The signal goes to the dual-gate-FET driver stage before finally radiating through the transmitting antenna. The output power is from 10…40mW. The radiated signal is also modulated by the gate circuit made of U1, U2, U3, U4. Gate U1 is a low frequency oscillator which generates a signal from 0.1 to 0.5Hz. This signal modulates the transmitter through the transistor T3. Fox Hunt Transmitter Circuit D iagram ...

Explanation of Operating Controls of CRO

Operating Controls of CRO The front panel diagram of a general purpose CRO is shown in the below fig. the panel controls are listed below. 1. Intensity (Brill): It controls the trace luminance. 2. Focus: It controls electron beam focus. 3. Astig: It controls defocussing that occurs due to astigmatism located on the front panel. 4. Tracerot: Trace rotation about the horizontal axis is possible by this potentiometer. Pic 1. Front Panel of CRO 5. Coupling (AC-DC-GND): It decides the mode of input coupling i.e. whether the input to the vertical amplifier is to be AC coupled, DC coupled or GND. 6. Volts/DIV: It controls vertical deflection co-efficient. 7. Position: it shifts the display vertically. 8. ...

Build a Ramp Generator Circuit using 555 Timer IC

We know that if a capacitor is charged from a voltage source through a resistor, an exponential waveform is produced while charging of a capacitor from a constant current source produces a ramp. This is the idea behind the circuit. The circuit of a ramp generator using timer 555 is shown in figure. Here the resistor of previous circuits is replaced by a PNP transistor that produces a constant charging current. Ramp Generator Circuit-using 555 Timer IC Charging current produced by PNP constant current source is i C = Vcc-V E / R E where V E = R 2 / (R1 + R2) * V CC + V BE When a trigger starts the monostable multivibrator timer 555 as shown in figure, the PNP current source forces a constant charging into the capacitor C. The voltage across the capacitor is, therefore, a ramp as illustrated in the figure. The slope of the ramp is given as Slope, s = I/C

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1977 DOD 250

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