The temperature stability of the Bitx version 3 board can be improved with a very simple modification. Replacing the 9 volt zener diode in the vfo circuit with a 3 terminal regulator. You can see a video documenting the stability test at Temperature stability test
The picture below shows the details.
After removing the 100 ohm resistor, carefully drill a small hole between the "0" and the "E". This will be furnish the ground to the regulator chip.
Scrape off the solder resist around the new hole and tin the bare copper with solder. Turn the board over and install a 78L08 or 78L09 with the flat towards the top of the board as shown in the top picture.
Remove R35 and D8. Install a 78L08 or 78L09 as shown in the picture below only solder yours. I left mine un soldered so I could have it lifted for better access in the picture. The flat goes toward the top of the board. The center lead of the regulator goes to the anode of D8. If you want to test it, measure between the empty hole left from the buttonhook of R35 and ground. If you use a 78L08, you may have to re-tweak your frequency slightly.
Thats all there is to it.