In the event you determine to substitute transistors with something similar you currently have, it possibly needed alter the collector voltage of Q1 by altering the value of R2 or R3 (because you change transistors, it changes this bias on the base of Q1). A little bit testing and patience might be in order.Īlmost all of the components values aren’t crucial, so you are able to attempt adjusting them to see what occurs. Then, using a non-conductive/non-metallic trimmer tool, fine-tune this capacitor to find the clearest reception. Set your FM radio for a clear, black spot in the lower end of the band (88MHz). The antenna is nothing more than a piece of 12″ wire or a piece of piano wire from 6″ to 12″. C2/C3 are electrolytic or can be tantalum types. C1/C4 and C5/C6 are ceramic capacitors, preferably NPO (low noise) types. To get a bit of tuning out of the coil you could put a 4-40pF trimmer capacitor (optional) parallel over the 1 uH coil, L1. It’s excellent for room monitoring, baby listening, nature exploration, and many others.Ĭ7 = 4-40pF trimmer cap (optional, see text) It possesses a range of approximately 1/4-mile (400 meters) or even more, depending on the line-of-sight, obstructions by big buildings, and so on. This small transmitter is simple to build and its transmissions could be picked up on any common FM radio. Fm broadcaster should be closed in a plastic so it can radiate.This is a mini FM transmitter built and powered using 2 transistors, designed by Tony van Roon. Optimum position is that the C3 allows obtaining a maximum signal when it is fixed on middle race.īecause we are dealing with a UHF transmitter, it is self understood that all components terminals should be as short as possible. If you can not find most, try to move the thread to be connected transistor (lower inductance) or to the edge of plate (higher inductance). Watch the signal received from the transmitter and adjust until C3 is obtained peak. To find the optimum position start by adjusting trimer C3, about the middle range of variation and mount thread connection about half the route that represents inductance. Lower frequencies require higher inductance, so connect it farther to PCB edge. Wire position depends on the frequency transmission. Also, on the front face of the PCB should be placed either a short connection (silver wire) that connects positive supply bar and inductance L1 made directly on the PCB and parallel to it. T1 transistor is mounted on the front of printed circuit board, as indicated by the dotted line on the drawing board.
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