Category «RF and Video»

Simple 9V Wireless Microphone FM Transmitter

This FM transmitter circuit can be used as a wireless microphone,  can be received by an ordinary 88- to 108-MHz FM broadcast receiver. For the power supply, this transmitter circuit is powered by a 9 V battery. To comply with the radiation limit of FCC rules, keep the antenna length under 12 inches. L1 is …

Fast Amplifier Circuit with DC Stabilization

This amplifier circuit combines the LT1010 and a fast discrete stage with an LT1008 based dc stabilizing loop. A differential stage which is single-ends into the LT1010 is formed by Q1 and Q2.  An output of 1 V pk-pk into a typical 75-Ω video load is delivered by the circuit.  With gain = 2, the …

Sferic Signal Simulator

Sferic signal simulator is used to produce an impulse  signal which simulates the waveform of a sferic, a radio atmospheric signals produced by a lightning strike. In time domain, the waveform of a sferic signal is a single high amplitude spike. When this pulse is analyzed in frequency domain, it will show a wide band …

Audio Power Amplifier for AM Radio

This is an AM radio power amplifier circuit. What is different with other general amplifier is that this circuit has a low-pass filter (passive type), built using R1C1 to limit the input-output frequency response. Additionally, a ferroxcube K5-001-001/3B with 3 turns of wire is used as ferrite bead  at output filter. All components should be …

Active Antenna With Gain (Booster)

This is an active antenna circuit with gain. This circuit is used to bost the signal. This circuit is made from a few transistors and other components. This circuit can provide RF gain of about12 to 18 dB. This circuit uses Q2 as a voltage amplifier. the RF signal direct-coupled from Q1’s Source terminal to …

Monitoring Off-Air Condition

The circuit of off-air monitor for SSB transmitter can be built by using combination of detector product with the crystal oscillator. This circuit is used for testing the audio at one point within band. The quality of audio will still constant, if loading and tuning of SSB transmitter are same over rest of band. The …

Simple SWR Meter Bridge

Standing wave ratio(SWR) is a ratio of amplitude of partial standing wave at maximum to amplitude at minimum. Using a Simple Swr Bridge circuit, a SWR can be measured. This circuit give a balanced VSWR meter perfectly, so adjustment is not required. This circuit can be made from a coupler which  formed by a 6.5-inch …