The functioning of all is provided by a microcontroller from MICROCHIP "PIC16F84" which provides support for buttons, LCD 2 lines of 16 characters and the circuit pll "SAA1057. The VCO is entrusted to the transistor Q8 associate of his two diodes varicaps "BB109, a floor buffer Q7 separates the VHF signal obtained in two ways, on the one hand to Q9 to enslave loop phase and on the other hand to the Q5 and Q6 together which takes care to amplify the signal before attacking Q11, a "BFR96" which plays the role of HF switch via a timer "NE555" which receives information from the push and "SAA1057" ensuring HF cutoff in the event of failure of a locking or unlocking of the pll.

This circuit is ideal for adding a low cost frequency display to a function generator or other design. I doubt if it is possible to get a cheaper design using off the shelf components!. In fact, I challenge anyone to make a cheaper design using garden variety components!. The upper frequency limit is dependent upon the upper limit of the 74HC390 chips which is roughly 40MHz.

This board is a RDS coder using an ATMEL AVR ATmega32. This board can be controled by a RS232 link, USB interface or SPI. TA data is displayed wiyth a LED and can be controled by : - Hardware input - RS232 - USB - SPI (not yet implemented)

Filter used for eliminate unwanted harmonic frequency at second and third. Notch filter, Band Pass Filter (BPF), and High Pass Filter (HPF) sometime combined in constructing LPF design. Schematic below for FM Broadcast Lowpass Filter 88-108 MHz. It has been tested with a good result. Note : Make the coils at 74 nH and trim them to adjust exact value.

Control up to three devices from a PC with FT232 IC (USB to Serial UART) from Future Technology Devices International FTDI. Circuit is simple and does not require external microcontroller or any type of firmware programming. PC control software written in VB6 is included.

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