02 February 2014

Building a Bench Frequency Counter

Ok, so here's a radio post.. well sort of.

I have been servicing my old Ham Radio gear and found I really needed a Frequency Counter to help me sort out drift problems with the VFOs.  Anybody who reads the RSGB publication Radcom, will know EI9GQ's articles Homebrew.   One of these was a frequency counter based on a pretty simple PIC circuit - so I decided to give it a go.

The hardest part in the end was getting the PIC programming software (pikdev.free.fr) running on my Ubuntu PC and talking correctly to the serial interface for the programmer.  But after some great help from a kind Frenchman, I did get that part working - all a bit strange to start with as I haven't worked with a PIC before.

The picture below shows the completed counter circuit connected in this case to a test crystal oscillator. (So thanks also to EI9GQ for those great articles.)

The next problem was getting the counter calibrated. Following EI9GQ's suggestion, my aim was to use the Russian frequency standard transmissions on 9.996MHz as my reference, and then sync the test oscillator to that.  With no general coverage receiver to hand, I used a combination of WEBSDR and a simple computer spectrum analyser to identify the Russian transmission and sync up the test oscillator. I think I managed to get it to with about 20Hz or so, which is not a bad start.

Just need to get it boxed now....


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