5W PLL FM Transmitter (PIC16F627A)

Posted on Jul 4, 2012

The transmitter includes RDS/SCA input and Audio/MPX input with optional preemphasis. It can be used with or without stereo encoder. Tuning over the FM band is provided by two buttons that control dual-speed PLL. The transmitter can work also without the LCD display. Some experience with building devices of this kind are highly recommended. After complete parts placement: Check that there are no shorts bridging adjacent tracks or pads. Check electrolytic capacitors polarity and semiconductor parts orientation. Make any duty load and connect it temporarily to the antenna connector. Use for example 2 or 3 bulbs (24V/170mA or 24V/3W) in parallel.

5W PLL FM Transmitter (PIC16F627A)
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For 0.05 MHz tuning step a 3.2 MHz crystal is required. In other case a 6.4 MHz crystal will make good work (tuning step 0.1 MHz). Any other crystal cannot be used. Wind all coils (except the L2) by a 0.8 mm wire. The Y1 package must be tied to ground! Make sure the Q3 terminals are as short as possible (about 2-3 mm above board). The 2N3553 case/heatsink can't be tied to ground! Be careful when soldering smd capacitors! To make the TR1 transformer, use specified number of turns on primary side and one turn on secondary side. The secondary wire should be quite thick but the primary can be as thin as you want. Wind on a 2-hole ferrite (material 61 or N1). Q1 - BF240 Q2 - BFG135 (BFG235) Q3 - 2SC1971 (2N3553) + heatsink Q4 - BC547B D1 - SB260 (1N5822, 1N581x) D2, D3 - BBY40 (BBY31) D4 - LED 5mm U1 - 78L09 U2 - TSA5511 (TSA5512, SDA3202) in DIL socket U3 - PIC16F627A in DIL socket (programmed) U4 - 78L05 R1, R2, R11, R17, R20 - 10k R3, R21 - 270R R4, R10 - 4k7 R5, R7, R12, R13, R16 - 680R R6, R14 - 18k R8 - 47R (33R if Q2 is BFG235) R9 - 18R R15 - 33k R18 - 3k3 R19 - 100k smd 1206 R22 - 91R R23 - trimmer 5k mini C1, C4, C9, C12, C13, C14, C15, C30, C31, C32, C33, C35 - 10n smd 1206 (C) C2, C20 - 15p (C) C3 - 10p (C) (15p if the PCB is single-sided) C5, C22 - 330p (C) C6, C28, C29, C34 - 100u/10V (E) C7, C26 - 10u/35V (E) C8, C17 - 22p (C) C10, C16, C23, C24 - 47p (C) C11,...

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