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nerosrevenge said:BC109C Transistor I was able to get BC107b.
4.7pF Capacitor. No luck got a 4pF and a 5pF. Will either do?
A BC107 will be fine, a BC109 is simply a higher gain, lower noise version, intended for high quality microphone and tape preamplifiers.
The capacitor isn't at all critical, I've often made bugs like this and simply twisted two pieces of insulated wire together for the feedback capacitor - about half an inch long, if you wanted to know.
Also I want to add an on/off toggle switch and an LED to indicate switch position. Green being on. I assume I will have to use a resistor ahead of the LED as a 9v battery will likely pop it. Here's the problem, I don't know the rating of the LED. I am pretty sure I need that to calculate the resistor I require correct? Any suggestions (short of going back to the store and looking it up among the several hundred LED's they have)? :shock:
I also got a proto board to make sure it all works.
LED current limiting resistors are easy, it's just ohms law - V=I*R. Rearrange it to give R=V/I, and fill in the blanks. You have a 9V battery, and the LED drops about 2V (2 is a nice easy figure!), so the voltage dropped across the resistor is 7V. Then decide on your current, it's a compromise between brightness and current consumption - lets say 10mA.
So we have 7/0.01 ohms, or 7/10 kohms - so 680 ohms would do nicely, but so would anywhere near - 560, 470, 820, 1K - it's not at all critical.
A proto-board probably isn't a good idea, this is a VHF oscillator, the stray capacitance in a proto-board could well upset things enough to stop it working at all - or at least shift it outside the VHF radio band.
I do have another question though. How do I tune the transmiting frequency of the circuit?
Simply move the windings of the coil apart or together, it's a lot easier to do than it sounds.