2014
RF Frequency Counter
I already have two frequency counters. One is a 15MHz ”Advance TC12A” (from the late 60s!) and the other is a 100MHz built into my ”Tektronix 2236”. But they're both big and bulky and sometimes I need a smaller more portable one for use with radios or similar. So, this is a design for a medium-sized TTL semi-portable frequency counter, mainly for radio frequencies. It's still in it's infancy and I have yet to build it but I'm pretty sure it would work in reality. I'm guessing it's capable of counting frequencies up to 45-50Mhz if using 74HC*** logic with good component layout.
It's a simple design that is easy to build and works okay, but it's very inefficient. Instead of utilizing the negative period of the gating (when it's not counting) to latch and reset, I use a decimal counter clocked by the timebase to count, latch, reset and wait. The ideal timing circuitry would be to use one-shots for latch and reset right after the gate period has gone low, thus quadrupling the sampling rate!
I found that by using a simple diode-array (gotta love those!) it's easy to implement decimalpoints and range lights if the gate time selector switch has two stories of contacts, which is nice.
A small frequency counter running on batteries would be really nice, perhaps I'll implement such an addon later.
Timebase |
Gating |
Counter |
Range Indicator |