2 Transistor FM TransmitterI accept acclimated a brace of BC548 transistors in this circuit. Although not carefully RF transistors, they still accord acceptable results. I accept acclimated an ECM Mic admit from Maplin Electronics, adjustment cipher FS43W. It is a two terminal ECM, but accustomed activating mic inserts can additionally be used, artlessly omit the advanced 10k resistor. The braid L1 was afresh from Maplin, allotment no.
UF68Y and consists of 7 turns on a division inch artificial above with a affability slug. The affability bang is adapted to tune the transmitter. Actual ambit on my ancestor acquainted from 70MHz to about 120MHz. The aeriform is a few inches of wire. Lengths of wire greater than 2 anxiety may clammy oscillations and not acquiesce the ambit to work. Although RF circuits are best complete on a PCB, you can get abroad with veroboard, accumulate all leads short, and breach advance at adapted points.
One final point, don't authority the ambit in your duke and try to speak. Body capacitance is agnate to a 200pF capacitor shunted to earth, damping all oscillations. I accept had some aboriginal duke acquaintance of this problem. The abundance of cadence can be begin from the approach section,and an archetype now appears in the Ambit Analysis section.
