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FM Stereo Test Transmitter

VHF FM and audio test signals

Published in issue 355, June 2006

This small signal generator uses an ingenious technique to generate a sine wave with very low distortion, a mono (L+R) baseband signal and an FM stereo signal.

Components

Resistors

R1 = 1k

R2 = 1M

R3 = 470k

R4 = 180k

R5 = 15k

R6,R27 = 100k

R7 = 39k

R8 = 2k4 (or 2k43 from E96 series)

R9,R10,R25,R26,R28,R29 = 10k

R11 = 5k1 (or 5k11 from E96 series)

R12,R13 = 120k

R14 = 47k

R15 = 1k8

R16, R18 = 22k

R17 = 1k5

R19 = 33

R20 = 2k2

R21 = 4k7

R22 = 68

R23 = 470

R24 = 56

R30 = 5k6

R31 = 330

R32 = 100

R33 = 820

P1 = 25k preset

P2 = 4k7 preset

Capacitors

C1 = 47pF

C2 = 56pF

C3 = 22nF MKT, lead pitch 5mm

C4,C9,C13,C15,C26-C30,C32 = 100nF ceramic, lead pitch 5mm

C5,C10 = 47µF 6V3 tantalum or radial electrolytic

C6,C12 = 68pF

C7 = 4nF7 MKT lead pitch 5mm

C8,C16,C17,C21-C25 = 1nF, lead pitch 5mm

C11 = 4µF7 16V tantalum or radial electrolytic

C14 = 220µF 10V radial

C18 = 18pF

C19 = 100pF

C20 = 22pF PTFE trimmer capacitor

C31 = 4µF7 16V radial

Inductor

L1 = 6 turns 0.8mm ECW or CuAg, internal diameter 5mm

Semiconductors

D1,D2,D5 = 1N4148

D3,D4 = BB405 (alternatives: BB205, BB505, BB208-03)

D6 = LED, red, low current

T1 = BF199

IC1 = 74HC4060

IC2,IC3 = 74HC86

IC4 = TLC277 (TS922IN)

IC5 = 74HC4066

IC6 = 78L05

Miscellaneous:

JP1 = 2-way pinheader w. jumper

S1 = on/off switch (and/or 2-way pinheader w. jumper)

S2 = 1-pole, 3-way switch (and/or 3-way pinheader w. jumper)

S3, S4 = changeover switch (and/or 3-way pinheader w. jumper)

X1 = 9.728MHz quartz crystal, HC-49/U, fundamental frequency, parallel resonance, load capacitance 30 pF, ±10 ppm, (see text)

BT1 = 9V battery with clip-on leads

BNC socket 50 Ohm (optional)

PCB, order code 050268-1