Had a couple of hours spare and decided to chuck this frequency counter together. [Pictures below]. I got it off an amateur based in India, Sunil Lakhani VU3SUA, on eBay. Sunil did also sell the BITX20 transceiver kits as well. Unfortunately he is no longer a registered user of eBay.
However, it now looks like Sunil VU3SUA is selling over the net. I found his website after searching for BITX20. The link for the frequency counter kit (sold as a digital dial) is here. The max frequency input is 40MHz.. It uses a pre-programmed PIC16F628A and the frequency counter module will be added to the BITX20, when I finally get round to building it 🙂
Derek M0XDC. Email firstname.lastname@example.org