I've got a reasonably decent record with my homebrew builds. Most of the things I've built have worked....sooner or later. However, I've probably built 6 or 7 cheapo frequency counters over the years and NONE of them have worked for me, despite the fact that (1) they're good circuits that I know to have worked for others and (2) they're really very simple circuits. I've taken into account the capacitance of the counter leads, "damping" effects, etc., and I have tried picking up the signal with coils or via direct contact at the oscillator output. Doesn't matter. I just can't get these little guys to work. In my own defense, I built the Oak Hills Research DD-1 counter and it works okay. It certainly wasn't cheap though. Unfortunately I need more than one counter and can't resist the allure of these cheapo counters on Ebay. I should resist though. I cannot make 'em work. Sigh.