Archive for the ‘RF and Video’ Category
Radio Frequency (RF) Watt Meter
For RF (radio frequency) transmitter experiment, watt meter is useful for optimizing the transmitter circuit. A simple RF watt meter circuit is shown in the schematic diagram below. Because circuit is not frequency sensitive, calibration is accurate on all HF bands. The sensitivity is affected by meter movement, number of turns in primary coil, and …[Read More]
10W 2 Meters RF Power Amplifier
When operating from 12.5 V auto battery, single TRW PT5757 transistor provides 10 W output. L1 is 4 tums No. 20 enamel and L2 is 10 tums No.20. Both, L1 and L2 has 3/32inch inner diameter. T1 is 4:1 transmission-line transformer made from 3-inch length of twisted-pair No. 20 enamel. This circuit can be used …[Read More]
This is a Low Distortion Crystal Oscillator circuit. This circuit generate a sinewave that has low phase noise and distortion. This circuit can be used to perform a crystal with less than 1mV dissipated in crystal. The crystal is used to filter the signal current. If the impedance loads is low, the JFET will drive …[Read More]
Voltage Controlled Oscillator with Varactor
This is a Voltage Controlled Oscillator (VCO) circuit. This circuit is based on Hartley oscillator. The frequency depend on the value of C1 and L1. The oscillation-frequency will change as the change of the capacitance in the varactor BB132 by The Vtuning voltage. The maximum frequency that can be changed is determined by th value …[Read More]
60-120MHz FM Receiver with AFC
We can say in simple words that AFC will lock the receiver to any valid RF signal. Below, we can see a basic block diagram of an receiver. The VCO is mixed with the RF signal which enter the mixer (yellow). The VCO can be a coil and a tunable capacitor. To bring out the …[Read More]
TC9400 VFC for PLL FM Demodulation
FM demodulation can be done with phase locked loop (PLL), and this method is common in high-end communication system. This system uses TC9400 that has high linearity. Using TC9400, the performance of phase-locked loop will increases greatly. That will give very precise tracking of Vout with respect to Fin. Here is the block diagram of …[Read More]
2 Transistors Mini MW Transmitter
This is a Mini MW (Medium Wave) Transmitter circuit. This circuit consist of combination of transistors SA103 and SA101. Those transistors is used as oscillator and modulation signal amplifier. Here is the schematic diagram of the circuit: The transistor is of germanium type, but I think you can replace it with silicon type from the …[Read More]
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