By Phil Rice VK3BHR

No, it doesn't measure your morse! Instead, it is a frequency meter that announces the measured frequency in morse code. It is another version of the Updated DFD published recently. Interested readers are referred to that article for a bit more detail.

How it works:

As with the previous design, it uses a PIC microcomputer to do all the work. The LCD display of the previous version is replaced by a "loudspeaker" connected to pin 18 via a resistor of 470 ohm or more.

Three jumpers connected to pins 6, 7 and 8 allow the selection of 8 different morse speeds, from around 8 wpm to 20+ wpm. The jumper on pin 8 has the greatest effect, the one on pin 6 has the least.

The PIC also has a 9600 baud serial ASCII output from pin 17. Pin 9 can be grounded to turn the morse off, leaving only the serial ASCII output active.

A jumper on pin 2 sets the count resolution, either 3 or 5 digits after the decimal point (1 KHz or 10 Hz resolution)

See the previous article for details of the other jumpers on pins 10, 11, 12 and 13.

The extra transistors on the circuit diagram implement a push button "start" function. At the completion of one measurement, the PIC turns its own power off. This is inherently troublesome as the PIC may change its little mind. The power control circuit prevents this. The whole lot can be deleted and replaced by a single pole switch if you want.

Getting the software:

Click this link for the assembler source code!

The last word:

Thats it! Three frequency meters from the one author may be one too many. I couldn't resist designing one for the CW/QRP/OT brigade. If you want a simple cheap frequency meter then you have to embrace modern technology. You could always make believe the PIC is not a computer, just a fancy frequency meter chip! 73 & happy constructing.