This superbly constructed and highly versatile little frequency counter was created by Finish Radio Amateur Matti Niskanen using a Cumbria Designs Minicounter. Matti describes his project and it's possible future evolution below;

Concept

"The outer dimensions of the counter are h=49mm, b=112mm and d=68mm. To support use with a wide range of input levels, I have used a frequency compensated 6 step attenuator and protecting diodes at the input. To extend the frequency range I have bought a prescaler SMD-chip that will work at up to 3 GHz (scaling factor 64, input 50 ohms). I've not yet decided whether to use this but if I do, the empty printed circuit board next to the GHz input connector is reserved for the prescaler stage. The prescaler device is very small and there is plenty of space for it. The BNC connector shown in the photograph is not intended for GHz use, but for my applications which are unlikely to exceed 500 MHz it is suitable. A front panel switch is used to select the input connector and associated scaling factor (B=64).

Also included in the box is an accurate 56 MHz xtal oscillator which serves as a convenient frequency marker or calibration source for the Minicounter. It's also handy just to check that everything is functioning OK."

Battery Power

"For portable use the counter can be powered from an internal 9 volt battery. To conserve battery power, there is a switch in the back of the instrument which turns off the back light and XTAL-osc but leaves counter and led light in the front on. For normal operation I use an auxiliary power adapter because the current demand with back light on and XTAL-osc on is 130 mA altogether. A front panel 3-position switch chooses which power source is in use. My power adapter gives 14.5 volts @ 130 mA and the regulator run so warm that I thought it was better to conduct the heat to the cover. The prescaler will need additional 25 mA if I will add it some day."

Professional Front Panel

"Nowadays I use Microsoft Power Point to make the front plates. Some of the newer CAD programs available these days might be more useful, but I'm used to using PP and it produces excellent results. As a matter of fact I have found the designing and making the front plate very satisfying and nice part of the enclosure building. It is so easy to make almost professional outlooks. I tried two different colour schemes; blue and green. I settled for the blue scheme which I prefer to the green.

The process needs a very good colour printer to produce acceptable results. First I design the layout and make several tests with ordinary black and white printer untill I'll get all the elements right. The colours I fix on the PC screen. Then I use the color laser printer and print a sheet of a special sticky paper which has ordinary copy surface on the other side and an adhesive surface on the other. I'll stick it on the front plate and then put on it a clear plastic film which also is sticky on the other side. It protects the printed surface from dirt and handling. It forms a kind of 'sandwich' construction. Both materials are available at local copy shops."

Images

(Click to expand)

Fig.1 Front panel

Fig.2 Rear panel

Fig.3 Front view, cover removed

Fig.4 Rear view, cover removed

Fig.5 Exploded view