PLL FM Transmitter 5W – Pira CZ

PLL FM Transmitter 5WThe FM transmitter circuit includes RDS/SCA input and Audio/MPX input with optional preemphasis. This PLL transmitter can be used with or without stereo encoder. Tuning range over the FM band is provided by two buttons that control dual-speed PLL. The transmitter can work also without the LCD display.

PLL FM Transmitter Schematic

Download Parts List here.

Printed Circuit Board (PCB)

PLL FM Transmitter PCB Bottom

PLL FM Transmitter PCB Top

You may choose between single-sided PCB (only bottom layer) and double-sided PCB (+ ground layer on the top). The difference is in output power. The double-sided PCB gives higher output power (this fact is not so interesting in rf issue).

PLL FM Transmitter 5W 2SC1971

Control Software for U3
The software for U3 is provided for download here: plltsa.zip (version 1.3). Please read included license text first.Suitable free PIC programmer is for example here: http://www.members.aon.at/electronics/pic/picpgm. Actually Pira CZ does not provide the PIC programming or complete kit sale for this device. Software modifications included: pll64.hex – 6.4 MHz crystal, pll32.hex – 3.2 MHz crystal, pll.asm – for any changes. Fuses: WDT: Enabled, OSC: INTRC-I/O, MCLRE: I/O.

Use the buttons to set the frequency. After a few seconds of idle the frequency is tuned and stored to EEPROM (icon of diskette). Finally the buttons are locked (icon of key) to avoid unwanted frequency changes. Unlock by pressing any button for a longer time.

The display and LED indicate PLL in-lock state. This state is also provided at pin 1 of U3. It can be used for control of additional power amplifier. When in-lock state is indicated, the PLL is switched to low speed for maximally flat low audio frequencies response.

Source: Pira CZ 5W PLL FM Transmitter