Bill of Soldersmoke has posted a very neat hack for the BITX40. An outboard analog VFO! It is as simple as it is clean and good. If you happen to be lucky enough to own a nice variable capacitor, this probably the one hack you need to make to your BITX!
So, this is, simply the VFO that he built :
It looks like this
Read more about his hack on soldersmoke blog .