http://www.rhelectronics.net/store/frequency-counter-diy-kit-module.html
The electrical circuit based on PIC16F628A microprocessor and 1/64 configured MB506 Prescaler. For better accuracy and stability, the MCU clocked by active 4.000MHz oscillator.
Prescaler block has about 50 ohm input impedance and two protection diodes for high frequency. MB506 divide input frequency by 64 and then trigger the MCU to count square wave signal. After the MCU complete count procedure, the processor will multiplies the number back by 64 to allow real frequency be displayed on LCD. In this way you can measure HF and VHF radio waves signals.
To measure signals under 10MHz, or audio frequency range, you can use "LF" input that drive input transistor amplifier stage directly. Be sure your signal has enough amplitude to trigger T2, usually its about 1V peak to peak signal.
Microcontroller program written in mikrobasic compiler. The kit has open source code for education purpose. Because the code size is less than 2K you can use Mikroe Demo Basic Compiler for PIC to modify the program. The kit sold with pre-programmed PIC and the software is compatible with both packages, economy and full.
