7 / 15 watt FM Transmitter PLL stereo digital circuit

A very high quality stereo FM transmitter circuit , thoroughly time tested ,highly reliable, crystal controlled PLL based for zero  frequency drift is reviewed below. The main circuit uses a very popular IC -KT0803L ,to develop two channel stereo audio modulated FM signal from76 MHz to 108 MHz covering the FM band of  88 MHz to 107 MHz feeding  to 3 stage buffering before being fed to the final power amplifier using most commonly used 2SC1971 for 7 watt or MOSFET -RD15HVF1 for 15 watt. But unfortunately most commercially available 2SC1971 or  RD15HVF1 are duplicate. Thus if one ventures trying any circuit with this power Transistor/ MOFET usually are unsuccessful. So I strongly recommend to go for readymade units. Aux audio is directly fed at pin 6 & 7 while for mic input it is amplified by LM358 and then…

Read More

How to get long range from FM transmitter

Antenna is the most important element There are 4 simple types that one can use for the FM transmitter. A—GP (Ground plane), B-Dipole, C- Reflected Folded dipole, D- Folded Dipole, E- Yagi. They are Omnidirectional, bi-directional, uni-directional & heavily directional. Discussed below a few for the amateurs. Complicated parameters like bandwidth. Gain, SWR, etc are all not covered for simplification except the impedance(Z) of the antenna which is important. The best way to increase the range of your FM transmitter is to use a matched antenna as per the impedance without which one gets very little range coverage. The cable, impedance matching, and height at which it is installed are also important. Any obstructions in the line of sight also affect the range. For example, one can get up to 1 to 2  KMs for a one-watt transmitter, 5 to…

Read More