200mW FM Transmitter

This FM transmitter is the 1st and 2nd Stage to the overall 3 stage 7 Watt FM Transmitter. This is the HPSO (Higher Power Suggestion Only) that I have spoken about on the 30mW FM Transmitter webpage. I have broken down the stages as to give one a little more lee-way into deciding which output wattage one would prefer...30mW? 200mW? or the 7 Watt? If you have never made a LPFM Transmitter before, I suggest you read my article on the 30mW unit.. just click here

1 Electret Microphone	12 PNP MPS2907 Transistor
2 1uF Electrolytic Capacitor	13 1uF Electrolytic Capacitor
3 4.7k Resistor	14 5-30pF Variable Capacitor
4 22K Resistor	15 L1- See text below
5 47k Resistor	16 IN914 Diode
6 NPN MPS3904 Transistor	17 5.6pF Disk Capacitor
7 1.2k Resistor	18 100 Ohm Resistor
8 5.6K Resistor	19 NPN MPS2222A Transistor
9 .001uF Disk Capacitor	20 5-30pF Variable Capacitor
10 1uF Electrolytic Capacitor	21 .001uF Disk Capacitor
11 4.7K Resistor	22 22 Ohm Resistor

L1 and L2 are made exactly the same. Using a 5/16 of an inch standard threaded bolt, take un-insulated 18 gauge solid copper wire and wrap three turns around it. Then back off the bolt and add a one turn tap. L1 one turn tap is from the diode. L2 one turn tap is from the collector of the MPS2222A Transistor. For a detailed description on how I made my 'tapped' air-core coils, please click here.

Looking back on this project, I do believe I had tried 9 to 15 volts from a power supply with good results. At 12 volts, this little jem should be around 200mW's of output power. If you are like me and have no test equipment, other than a homemade watt meter and a DVM, you can locate the main transmitting frequency by just using a typical AM/FM radio and switch it to FM...then go all the way to the lowest frequency...all the way to the left of the radio dial...which is around 87 Mhz...that is where I have adjusted the coils for. You will have to experiment with this as the transmitter will not only put out the main oscillating frequency, but also harmonics...get together with a friend and have him gradually walk away (with AM/FM radio in hand), until he cant' hear you anymore. He should get a few city blocks away...if you are on the 'main' transmitting frequency...if not, he won't get too far at all.

For other explanations or advice on concerned areas, do drop me a line at...