I was in need of a frequency counter while trying to work on an analog VFO circuit, so decided to make one. There are 3 types of inputs, a TTL, RF, and microwave prescaler which should work up to 2.4 GHz. Each input has a schmidt trigger going into a binary ripple counter. In addition, the RF input has an amplifier at the input for low level signals and a selectable high impedance or 50 ohm input.
A rotary encoder selects between the various inputs.
I really like the look of the 7-segment displays, so this project was a good excuse to use them.
One major weakness of this design is that I didn't use a precision frequency reference. Optimally, this should be a precise clock, preferably temperature controlled. Perhaps for my next iteration, I'll include a provision for using an external 10 Mhz reference.