Ramsey Electronics FT146 - Manual (Page 11)

FT146 • 11
❒ 41. Install R7, 470 ohm (yellow-violet-brown).
❒ 42. Identify Q1, a 2N3904 NPN transistor (marked 2N3904). Install Q1,
observing correct placement of the flat side.
❒ 43. Install Q2, another 2N3904 NPN transistor (marked 2N3904).Observe
correct placement of the flat side.
❒ 44. Install C27, 15 pf disc capacitor (marked 15 or 15K).
❒ 45. Install trimmer capacitor, C43 (black body with orange top). This
trimmer is used for setting the FT146 exactly on frequency.
❒ 46. 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. Notice that there are two holes "kitty-corner" around Y1. These
holes are used to supply power to the optional crystal oven; they are not
used in the standard FT146 kit.
❒ 47. Install D3, zener diode (gray body with black band). A zener diode
functions as a voltage regulator since it has the property of holding the
voltage across it constant. In this case we wish to hold the voltage to the
crystal oscillator steady to keep us on frequency, even with a poorly
regulated disc capacitor power supply.
❒ 48. Install R28, 100 ohm (brown-black-brown).
❒ 49. Install R1, 1K ohm (brown-black-red).
❒ 50. Install JMP3, another wire jumper.
❒ 51. Install C3, .01 uf (marked .01 or 103 or 10 nf).
❒ 52. Install C9, .1 uf disc capacitor (marked .1 or 104).
❒ 53. Install C23, .001 uf disc capacitor (marked .001, 1 nf or 102).
❒ 54. Install C44, .001 uf disc capacitor (marked .001, 1 nf or 102).
❒ 55. Install C8, .001 uf disc capacitor (marked .001, 1 nf or 102).
❒ 56. Install C5, .01 uf disc capacitor (marked .01 or 10 nf or 103).
This completes assembly of the crystal oscillator section of our FM transmitter.
If so inclined, we could connect up some power and actually "fire-up" the PC
board so far. We'd only be producing a signal at 1/9 of the carrier frequency
though, since we've yet to build the multiplier stages.
❒ 57. Install R3, 47K ohm (yellow-violet-orange).
❒ 58. Install Q3, 2SC2498 or 2SC2570A NPN VHF transistor (marked C2498
or 2570A). Position the flat side as shown on the parts layout.
❒ 59. Install C28, 39 pf disc capacitor (marked 39 or 39K).