>>  Can I suggest you forget the 555s and simplify the thing completely?
>Use one measuring circuit (such as a 555 or gate-logic RC timer) and
I'm also want to build a R/C transmitter.
The hard part for me is the RF stage. Can someone help me in this (40MHz).
But, if you plan to use a PIC in your design why not use a PIC with A/D
converter ? Much sipmlier design and programming needed.