A very useful device and easy to build is this frequency meter/digital scale developed by IK3OIL. The project is well known, it has been posted many years on various sites and publications by homebrew amateur radios. So, no need to comment much about it. Circuit diagram, PCB as well as many construction details you can find in the original document on this link.
I remind here some of the main characteristics of the device:
- maximum input frequency is 50MHz;
- it uses a PIC16F84 microcontroller and a 1X16 LCD display;
- input amplifier stage with 2N2369. I used 2N2221 and works very well;
- 9V battery supply, with 15mA current consumption (without display backlight);
- two programmable buttons for IF set, in three modes VFO+IF, VFO-IF and IF-VFO;
- a prescaler can be connected to the device etc.
The PVC box that I used is called KM-56. You can find it in most of the electronic equipment stores like TME, Farnell etc. The entire assembly was perfectly fitted into this little box. For the front panel I used a very handy and easy method. I draw the panel in Autocad, then printed at 1:1 scale and laminated with transparent plastic cover. The result was a nice looking frequency meter!
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