With this three stage transistor transmitter we can create and broadcast our mini radio station. We using S9018 transistor because it can handle very high frequencies, up to and including the VHF band. The first transistor on the left is a microphone audio amplifier for modulation. The gain can be adjusted with the potentiometer. The second transistor is the oscillator with a range of 80 to 103 MHz. The frequency can be changed with the upper coil 4T5 by pulling it slightly apart. The signal from the oscillator is very small, so that still needs to be amplified. The right most transistor is therefore an RF amplifier. This amplifies the signal from the oscillator to feed to the antenna. This transistor also immediately provides more stability, because the oscillator is not directly connected to the antenna.
Build Accurate LC Meter and start making your own coils and inductors. This LC Meter allows to measure incredibly small inductances making it perfect tool for making all types of RF coils. LC Meter can measure inductances starting from 10nH - 1000nH, 1uH - 1000uH, 1mH - 100mH and capacitances from 0.1pF up to 900nF. The circuit includes an auto ranging and reset function to make sure the readings are as accurate as possible ... [more]