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Mini-Emițător FM #1: Parts List

This document provides a parts list and instructions for constructing a miniature FM transmitter that can transmit up to 1/4 mile. It consists of common electronic components including resistors, capacitors, transistors, an inductor, and requires a power source. The instructions explain how to assemble the components on a small circuit board or breadboard, how to tune the transmitter frequency using a trimmer capacitor, and tips for locating the transmitted signal on an FM radio.

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vladareanucatalindan
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67 views2 pages

Mini-Emițător FM #1: Parts List

This document provides a parts list and instructions for constructing a miniature FM transmitter that can transmit up to 1/4 mile. It consists of common electronic components including resistors, capacitors, transistors, an inductor, and requires a power source. The instructions explain how to assemble the components on a small circuit board or breadboard, how to tune the transmitter frequency using a trimmer capacitor, and tips for locating the transmitted signal on an FM radio.

Uploaded by

vladareanucatalindan
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as ODT, PDF, TXT or read online on Scribd
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Mini-Emitor FM #1

Parts List
R1,R4,R6 = 10K C1,C2 = 0.1uF Q1,Q2 = 2N3904
R2 = 1M C3 = 0.01uF L1 = 0.1uH
R3 = 100K C4 = 4-40pF
R5 = 100 ohm C5 = 4.7pF
R7 = 1K

Construction
This miniature transmitter is easy to construct and its transmissions can be picked up on
any standard FM radio.
It has a range of up to 1/4-mile (400 meters) or more, depending on the line-of-sight,
obstructions by large buildings,
etc. It is great for room monitoring, baby listening, nature research, etc.
L1 is 8 to 10 turns of 22 gauge hookup wire close wound around a non-conductive 1/4-
inch diamter form, such as a pencil.
C4 is a small, screw-adjustable, trimmer capacitor.
Set your FM radio for a clear, black space in the lower end of the band (88MHz). Then, with
a non-metallic/non-conductive
trimmer tool, adjust this capacitor for the clearest reception. A little experimenting and
patience may be in order.
Most of the parts values are not critical, so you can try adjusting them to see what
happens.
If you decide to substitute transistors with something similar you already have, it maybe
necessary adjust the collector
voltage of Q1 by changing the value of R2 or R3 (because you change transistors, it
changes this bias on the base of Q1).
It should be about 1/2 the supply voltage (about 4 or 5v).

Notes
The default for the capacitors type is ceramic, preferably the npo 1% (low noise) type or
equivalent. But basically
nothing critical here.
Use any capacitor you have laying around, but NO electrolytic or tantalum caps.
Only if you intend to use this circuit outside the home you may want to select more
temperature stable capacitors.
To find the signal on your receiver, make sure there is a signal coming into the
microphone, otherwise the circuit wont
work. I use an old mechanical alarm clock (you know, with those two large bells on it). I put
this clock by the
microphone which picks up the loud tick-tock. Im sure you get the idea Or you can just
lightly tap the microphone
while searching for the location of the signal on your receiver.

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