chemelec cd4046
thx alot IanP
Added after 4 hours 43 minutes:
Sorry guys
but now my instractor said
"no use of any chips you can use colbet or hartly tuned circuits "
but the problem of these circuits is the coil
we need coil of 70 mH
because the varying capasitors in the market are between 10&40 PF
so if there is no way to design this VCO without chips or op-amp's
i will make coil with large inductance
so any one know how to calculate the inductance using iron core
what i know is the inductance is a function of
No of turns,wire length,............etc