Direct Conversion HF Transceiver - VK3AJG
After about a 15 year absense from amatuer radio, I decided it was time to get back into it. 
This time I won't buy any commercial gear, and will make it all myself.
Most of the back end design for this transceiver was taken from the, "NO-TUNE SSB/CW Transceiver"
by Matjaz Vidmar, S53MV.  This project is also in the 2005 RSGB Handbook.

This project is a work in-progress.  It was originally going to be only a single band transceiver,
hence the single vco.  But somewhere along the way I decided to make it multi band (80/40/20)
and add a pll synthesizer.

NOTE: This is a work in-progress, not all circuits have been tested, and
             diagrams may not be correct at this time.  Updated schematics
             will be posted when everything is working.

                   block diagram
Block Diagram
Status as at 25/05/2006:  I now have the VCO working, and am surprised how stable it is when
running uncontrolled. After checking the demodulator board and IF amp board was working,
I connected the mixer board, and was surprised to hear signals on 80m, with only a clip lead
connected to the mixer input. 
The Digital Display board is also working ok, but I need to replace the display driver resistors with
lower values (as the LED's were a bit dim in daylight) before fitting it back in the unit.
Audio quality of received stations is nothing short of excellent.
demodulator.png  The Demodulator board       camera.gif

if-amplifier.png  The IF Amplifier board         camera.gif

modulator.png  The Modulator board

mixer.png  The Mixer board  (old design)                                     new mixer  (new mixer design)

VCO-Multiband.png  New Multiband (80/40/20) VCO design                       vco.png  The VCO board (old design)          

s-meter.png  S-Meter board

f-counter.png  Frequency counter board          photo

Synthesizer-main.png  PLL synthesizer  (without extension memory board)


                      Extension memory board for synthesizer


bandpass.png  80/40/20m Rx/Tx Bandpass filter

control.png  Control board (dial i/face, band switch, tx/rx, etc.)

power-filter.png  DC Power Filter


                      Shaft Encoder for PLL       shaft encoder


                      PA Stage


                      Low Pass TX Filters


   rig bottom viewDemodulator, Modulator, IF Amp & Control borards.

Last Update:  25/05/2006