Thursday, 24 April 2014

35 MHz frequency counter from India

One of the most useful tools for a radio operator is a frequency counter. With PIC's available these days it is not that difficult to build one yourself. The counter presented here makes use of a 1x16 character display HD44780. 
Those displays are for sale for appr. $2.50 at eBay. A PIC 16F628A, a 4 MHz xtal and some discrete components is all you further need.




The design comes all the way from India: http://www.hamradio.in/circuits/freq_counter_lcd.php
The HEX-code for the PIC is shown at the bottom of the webpage. The design allows you to set a lot of different IF frequencies (including IF = 0 Hz).




I was really surprised to see that the counter could measure frequencies much higher than 35 MHz. In this case a frequency in the 4 meter band (70 MHz) is shown.  



Note: According to Rinus Jansen from Kent Electronics the higher max. input frequency can be explained by the fact that a -628A pic instead of the old -84 pic is used.

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