Disclaimer: The circuits enclosed are for experimental purposes only. They are not intended for illegal use. When you apply their use in an illegal application you subject yourself to a shitpot - and world of shit if you are caught. Please check the Local, State and Federal laws including the FCC rules and regulations to determine what you can and cannot do.
Component Sizes: The artwork is drawn for 1/4 watt resistors. Keep the resistors and capacitors to 5%. 1% are expensive and 10/20% components are useless. 5% will keep the circuits and each part within its working range. Any size components can be used - just bend the leads to fit the holes.
Capacitors: All small capacitors are of the ceramic type 2.5 MM. The electrolytic are marked with a +  and are 2.5 MM in size. The adjustable ones are TZ03 5.1 MM Trimmers. If the holes don't line up on the boards for whatever size you are using, just bend the leads to fit. Use Low Voltage Types.
Surface Mount: Althought virtually all of the artwork is TTH ( Thru The Hole ) boards in these circuits, For years I have used the same TTH artwork for surface mount. Here is how I do it. I simply reduce the size of the solder side of the board to 1/2 or smaller until a standard surface mount resistor will connect between two of the holes on one of the resistor slots. Generally everything else will fit. I then solder the SMD parts directly to the solder side of the board.
Stripboard Layouts: You can use regular perfboard that has no solder side ( Holes Only ). Simply use the "Screen Layout" supplied, push the components through and solder the leads to each other.
Microphone Element: Any small electret element.
RF Coils: All rf coils in these circuits are between 3/16 to 1/4" in diameter of between 3 to 6 turns using standard magnet wire between 18 to 23 AWG. The determining factor of what frequency the transmitter will operate at is based on the parallel combination of the coil ( Usually called L1, etc. ) and the capacitor in whats called the tank circuit. As a general rule, the more turns, the lower the frequency - and the less turns the higher the frequency. All coils are airwound using a drill bit of 3/16" or 1/4." Generally the coil is a fixed amount of turns and the capacitor is adjustable. If the capacitor in the tank circuit is a fixed one - just spread or compress the turns and it has the same effect.
Transistors: Although the circuits enclosed are specific in the transistors they specify, it has been my experience that most any quality NPN - VHF transistor will work in these small transmitters. That is based on experience. The factor that really determines if they work or not is usually the feedback capacitor that is connected from the emitter to the collector of the rf section - usually between 3 to 10 PF. That capacitor causes instability in the transistor and causes it to oscillate so if you don't use the specific transistor the circuit requires, try going lower or higher on that particular capacitor to get the transistor to oscillate.
Fleeting Thoughts: Having specilized in the generation and transmission of radio frequency energy over the past 60 years, I can pretty well look at a circuit and tell if it is going to work or not. From what I see in the circuits I have picked for this website, they all work. If your circuit does not work it is usually the result of a wrong component, bad component or a part in the wrong place, or an improper feedback capacitor from the base to the emitter of the final rf. All of the circuits listed have a link enclosed that will direct you to the original website where the circuit has been posted for all of the circuit specifics and details so go there - rather than email me for any details.

I put a great deal of time building this site based on hundreds of emails from folks that found me on my regular website Bugplan.Com looking for these types of simple transmitter circuits. I did the work and it is presented in these pages. If you need Professional Circuits, please click into the Blue Link ( Bugplan.Com ) directly above this line.

Enjoy, John.
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