Low Cost Multifunctional Frequency Counter


We are introducing a low cost multifunctional seven digit LCD frequency counter, for your HAM radio shack. This frequency counter is designed in such a way that it can be used for direct frequency measurement or with any of the commercial / home made radio/transceiver as a digital frequency display. The power consumption of the counter is very low. It could be operated with even an ordinary 9V battery for a long period.

This frequency counter contains only a few components. The brain of the unit is a PIC 16F84 micro-controller. The LCD display used is a state of the art, commonly available 16 characters dot matrix in one line unit. The other main attractive feature is the use of a single transistor as the input amplifier, which will give a sensitivity of less than 150 m.V with a very high bandwidth. With this, the counter is useful for the measurement of a wide variety of input wave forms without loosing the accuracy. The counter is capable of measuring frequency up to 35MHz in normal condition and is suitable up to 3.5GHz with pre-scalar.


  • 10 Hz frequency resolution.
  • Direct frequency measurement.
  • Seven offset channels selectable with a push button.
  • Each offset channel got 3 options (VFO + IF) , (VFO IF), ( IF - VFO ) selectable with a three position switch.
    • Eg.1 Suppose IF is 9MHz (9MHz SSB filter using with home made TRX) and VFO is 2 MHz you have to select the third option (IF-VFO) ie (9 2) = 7 for 40 mtr operation.
    • Eg.2 Suppose IF is 9MHz and VFO is 5MHz you have to select the first option VFO+IF ie 9 + 5 = 14 for 20 mtr operation With this offset channel selection option you can simply input the VFO frequency to the counter with out any conventional mixing for displaying the operating frequency.
  • In each of the above offset channel option, it is possible to select USB/LSB displayed as N / R (Normal / Reverse) selectable with another 2 position slide switch.

Any IF frequency can be programmed into the available seven channels, as per the requirement of the user . We have pre-programmed the most commonly used frequencies such as 9, 1.6, 10, and 4 Mhz.




PCB Design and Lay out

Bottom View (Size 80mmX52mm)     Component side view

Circuit of Frequency counter
Download the circuit diagrum

Hex file for programming PIC16F84A can be download from Downloads [1] in this site

PIC16F628A Version

This is another version of frequency counter using PIC16F628A instead of PIC16F84A written by VU3CNS using the same circuit shown above. 10 IF offsets and 1 direct counting options are included. You can select a Gate period of 1 Sec or 125mS with 1 Hz or 10Hz accuracy respectively. Download hex, source (asm) files and circuit from [2].

The components used in this circuit are easily available in the electronic market. This circuit can be assembled for less than Rs.500/-.

We wish you good luck in this new project and happy home brewing. This frequency counter will be a great asset for your HAM Radio shack. If you require any assistance while assembling the unit ,you can get clarifications from VU2XTO, VU2RYL or VU2ITI. Your suggestions and comments on this project may be put to the Forum on this web.


[1] Hex file for programming PIC16F84A
[2] Hex, Source (asm), and Circuit for PIC16F628A Version

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