Build a PIC controlled DDS VFO, 0 to 6 MHz

Click a picture to zoom

Files contained in MINIDDS.ZIP:

  readme.txt      Read this first!  compplac.pdf    Component placement in PDF format  schema.pdf      Schematic diagram in PDF format  top.ps          PCB top copper layer in Postscript format  bottom.ps       PCB bottom copper layer in Postscript format  ad9832_4.asm    PIC assembly source code  p16f84.inc      Needed for assembly of ad9832_4.asm (for 'F84)  p16c84.inc      As above but for 'C84  vfo5x7f.hex     PIC16F84 program for LCD with 5x7 font  vfo5x10f.hex    PIC16F84 program for LCD with 5x10 font  vfo5x7c.hex     PIC16C84 program for LCD with 5x7 font  vfo5x10c.hex    PIC16C84 program for LCD with 5x10 font  filtresp.pcx    Computed frequency response of lowpass filter

Download MINIDDS.ZIP (186K)

Download MINIDDS.PDF (209K)

If you prefer to control the DDS module from a PC (instead of using a PIC), try this:

Download PCVFO.ZIP (18K)

The zip archive contains a single file, VFO.EXE. It is a DOS program but it runs fine in a Windows 95/98 "DOS bubble" as well (see screenshots above).

Are you looking for a DDS based 136 kHz longwave transmitter exciter?

Have a look at G0MRF's page

Specifications:

Start-up frequency: 137.00000 kHz
Tuning range: 135.70000 to 137.80000 kHz in 0.25 Hz steps
DFCW offset: 0 to 50 Hz adjustable in 0.25 Hz steps
The dial can be locked to prevent inadvertent QSY
Calibration: +/- 200 ppm, stored in EEPROM.
Actual DDS output frequency is 4 * dial frequency

Schematic and source code for the PIC controller is available here:

Download the PIC program lwex.zip

The PIC program is written for the free version of the CC5X C compiler which is available atwww.bknd.com

Click the schematic for a full size version

Almost any 2x16 character LCD module with Hitachi HD44780 controller chip will work.The LCD pin numbers on the schematic are not valid for all LCD modules. Please checkthe actual signal names on your particular LCD module.

The selected DFCW frequency offset will be added to the output frequency when theDFCW input is grounded. This input has a weak pull-up in the PIC.

The encoder inputs also have internal pull-ups in the PIC.

The switches "LOCK", "DFCW" and "CAL" are momentary pushbuttons.

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