
FHT-1 • 12
uses the same pin configuration as one. When installing be careful not to
bend the solder pins, and make sure to push the switch flat to the board.
30. Install C41, 10 uF electrolytic. Watch that polarity!
31. Install R31, 1K ohm (brown-black-red). Notice that this is another
“stand up” resistor.
32. Install C48, 150 pF disc capacitor (marked 150 or 151).
33. Install C40, .01 disc capacitor (marked .01 or 103 or 10nF).
34. Install small signal diode D5, 1N4148 (opaque orange/red with black
band). Diodes are polarized, so be sure to orient the part correctly! See
the parts layout diagram for correct placement.
35. In the same manner install diode D2 - remember that polarity!
Whew! Time to take a breather. We’ve just completed the entire
microcontroller section of the transmitter. Now is a good time to recheck your
work paying careful attention to parts orientation, Also, look over the solder
side of the PC board for any solder bridges or splashes. “Touch up“ any
connections which are less than perfect.
Now we’re going to begin building the 144 MHz transmitter section of the
unit. While you shouldn't be afraid of this, please try to remember that at
VHF frequencies component lead length can be the difference between a
working unit and a marginally performing one. Follow the instructions
carefully and your unit will perform admirably with no trouble. Be sure to fit all
components as close as mechanically possible to the PC board for best
results.
36. Install R14, 10K ohm (brown-black-orange).
37. Form and install jumper JMP4.
38. Install C35, .1 uf (marked .1 or 104).
39. Install R13, 5K stand up trimmer pot. This is the modulation
adjustment control.
40. Install R47, 4.7K (yellow-violet-red).
41. Install R12, 1K ohm (brown-black-red).
42. Install Y1, crystal. This is the "heart" of the FM transmitter,
producing the initial signal which is multiplied and amplified up to the
final transmitted signal.
43. Install D1, FS4059 varactor diode (small black body with yellow
band). Varactor diodes act as voltage variable capacitors. In this case,
D1's capacitance is varied by the amplified voltage from the
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