Radio circuit diagrams electronics projects for radio transmitter, radio receiver circuit, rf amplifiers, rf boosters and some other related RF circuits like: fm antenna booster, microwave transmitter and wireless modules.
A very nice simple and useful circuit diagram of an FM transmitter is sown in this schematic . This fm transmitter circuit is very simple and it has a acceptable transmission . The signal transited from this fm transmitter circuit can be received at almost 300 meters in open air The circuit require a 3volts operating voltage and can be tuned anywhere in the FM band.
You can use this rf transmitter circuit to transmit signal from your house to garden or from room to room . To listen the signal you can use any radio (portable or not ) that can work on FM band .
The coil should be about 3mm in diameter and 5 turns. The wire is tinned copper wire, 0.61 mm in diameter.
After the coil in soldered into place spread the coils apart about 0.5 to 1mm so that they are not touching. If you don’t have a trim cap you can use a fixed value capacitor and you can vary the TX frequency by adjusting the spacing of the coils or placing a small piece of ferrite inside the coil , but the better way to change the transmission frequency is to use a variable capacitor .
Connect a half or quarter wavelength antenna (length of wire) to the aerial point. At an FM frequency of 100 MHz these lengths are 150 cm and 75 cm respectively.
The calibration of this rf transmitter circuit is very simple and you need just to place a radio at some distance from the transmitter and set it somewhere about 89-90MHZ( chose the transmission frequency ) and after that vary the transmitter oscillator frequency , by modifying the value of the capacitor . The transmission frequency is set to the desired frequency just when you can hear the transmitted signal.
A very simple electronic phone fm transmitter can be constructed using this circuit diagram . This FM transmitter circuit can be attached in series to one of your phone lines to transmit the received signal on the FM band . When you pick up the phone , signal is present on the line the circuit will transmit the conversation on a short distance. This phone fm transmitter circuit will not need any power supply or battery , because this circuit use the signal from the phone line for power .
No aerial is needed - it feeds back the RF signal into the phone line which radiates it in the FM band. The frequency of transmission can be adjusted by the trimcap.
To set the desired operating frequency of this phone fm transmitter circuit you can take your phone off the hook and turn on an FM radio at about 93 MHz and tune the circuit into transmission . After that , take a portable FM receiver and search the signal from the phone line.
Usually this type of circuit should be calibrated , but it works fine without any calibration .
The T1 transistor can be BC547 or BC548 and the T2 transistor can be ZTX320 or similar type .
All diodes used in this fm transmitter project are 1N4148 type and the C8 capacitor is a 5-20pF trimcap (variable capacitor ) .
>For this transmitter you need to construct the inductors so : L1 has 6 turns enamelled Cu wire , L2 has 8 turns enamelled Cu wire and L3 has 6 turn tinned Cu wire .
A very simple and useful antenna amplifier can be constructed using this circuit diagram . This antenna amplifier is very useful for 35kHz-150Mhz frequency band . This antenna amplifier circuit is based on transistors and has a low 3 dB non-linearity and a high gain of 43 dB . The input and output impedance for this rf amplifier is 75 ohms . The L1 and L2 radio frequency coils are constructed from a 0.25 mm CuEm wire , with a 5 mm diameter . Both coils require 10 number of turns .
All used transistors are of the same type and can be BF183, BF200 or other similar type . The total consumption of this rf amplifier is very low , the circuit will need only 20 mA .
This rf amplifier circuit needs to be powered from a 12.5 volts DC power supply circuit .