Instruction manual

SM100 • 13
 31. Install Q5, FET marked 2N5485 or MPF102. Make sure that the flat
side is facing C13.
 32. Install C10, .1 uF capacitor (marked .1 or 104).
 33. Install D6, a varactor diode. It looks just like a transistor with only
two leads, and is marked MVAM108. A varactor diode acts as a voltage
controlled variable capacitor. By increasing or decreasing the DC
voltage into the varactor, we can tune the circuit to the desired
frequency.
 34. Install C8, a 10 uF electrolytic capacitor. Remember that the lead
closest to the black stripe is the (-) lead. This lead should be towards
the outside of the board when properly installed.
 35. Install R10, 100K ohm resistor (brown-black-yellow).
 36. Install R13, 1K ohm resistor (brown-black-red.) This resistor must
be mounted standing up. To do this, first insert one of the leads all of
the way into the hole marked with a circle on the parts layout diagram.
Next, bend down the other leg and insert it into the other hole. You
should bend it down so the resistor is still standing, but there is no
excess wire standing above the circuit.
 37. Install R12, 100K ohm resistor (brown-black-yellow).
 38. Install Q4, an NPN transistor marked 2N3904. Q4 and Q5 amplify
the incoming signal so there is a minimum signal loss going to the
receiver.
 39. Install R15, 470 ohm resistor (yellow-violet-brown).
 40. Install C6, .1 uF capacitor (marked .1 or 104). C6 is also used to
filter off noise.
 41. Install R9, 10K ohm resistor (brown-black-orange). Be sure that it is
mounted standing up like a soldier standing at attention (or our college
intern student being questioned about various lunchtime desserts!).
 42. Install C7, .01 uF disc capacitor (marked .01 or 103). C7 and C8
are used to keep the voltage oscillator from oscillating.
 43. Install R14, 75 ohm resistor (violet-green-black).
 44. Install Q3, NPN transistor marked 2N3904. This transistor is used
as a 12 volt regulator. By keeping a constant 12V on the base, we know
that the emitter voltage will always be 11.3V! Don’t forget to use the
correct polarity. The flat side should face L2.
 45. Install D5, 1N4148 diode (glass body with a black band). D5 is used
to protect the circuit against current in the wrong direction.