Here is the latest and greatly improved TX200 VFO/VCO FM transmitter. The most versatile transmitter to date that can be turned into high fidelity stereo PLL based 200mW FM transmitter. It is a perfect circuit for transmitting your music around the house and yard. TX200 uses only two coils; one in the oscillator and the other one in the 200mW VHF amplifier so it should be fairly easy for anyone to build.
It also includes built-in pre-emphasis and C5 for enhanced sound quality. While assembling the transmitter care must be taken to make sure that C1 is directly connected to L1 and C9 to L2. These caps eliminate the distortions form the DC supply and improve the sound quality greatly. 9V voltage supply is also very important because it provides the exact amount of current to Q1 to produce loud and clear sound quality.
TX200 comes with built-in LED based power meter. This is a very helpful tool that will tell you if your transmitter’s oscillator is working properly. If RF signal is transmitted the LED will illuminate. Besides that, it will also give you a quick visual way to check how much power is being transmitted. I highly recommend that you have the transmitter and power meter on the same PCB. If you like to experiment a lot, you will appreciate this inexpensive but externally helpful addition.
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