Another cool microcontroller project from jesper. Counter measurer using microcontroller AT 90S2313, you can use ATtiny 2313 to replace it. It could be a simple digital counter count up at 35-40Mhz. The software written in C code.
"It uses only 4 chips - 3 HC TTL's and an Atmel At90S2313 microcontroller. It has a 5 digit LED display plus one used as a band indicator. Even with the LED display, the current consumption is less than 50 mA. It counts up to at least 52 MHz. I couldn't find any signal source in the lab that could supply more than 52 MHz, so it may go a bit higher, but the fClock(typ) for the HC590 is about 35-40 MHz, so you shouldn't really count (no pun intended) on more."View Schematic and download source code for counter measurer.