This is my old blog, not updated anymore.
I got design and pcb layout from F6BQU for making Automatic Picture Transmission receiver. You can visit his web page for more details http://lpistor.chez-alice.fr/meteo2.htm. Further, added PLL MC 145152, NE 567 & PIC16f628 to it . Wrote small program for PIC16F628 according to my need. Frequency is set by diodes, Pic16f628 selects CH and scans it by bringing it to logic zero. On every channel it waits for about 2 sec and looks for 2400hz tone, tone detection is done by NE567. If tone is detected then PIC locks the CH for 15 mins, it sounds buzzer alerting that wx sat has arrived (as the speaker is off). Next PIC activates small relay for about 1 sec, this relay is configured to desktop pwr sw, which is configured for waking up from hibernation in windows xp . At the end of 15 min again the relay is activated for 1 sec puting back desktop in hibernation and scanning rusumes again. Wxtoimg program is always running and waiting to decode. Open squelch scanning is done so that even weakest signal is detected, atleast 2 min before the actual wxtoimg program starts(above 10 degreee elevation). This 1-2 min give sufficient time to start / wakeup PC . This trick worked very nicely, it saved lot of energy consumed by desktop pc. I have upgraded to Intel atom Desktop computer. Even low power computer as the CPU is just 3 watts. Most parts of this project were obtained from juck rf boards.
SCHEMATIC (F6BQU)
In my project I am not using doppler correction section.
