ok, many thanks for the nice idea, i can do the capacitor splitting, but i've put for test the 2 resistors at the COIL sides, as in the last corrected diagram attached, and the circuit go on to transmit and receive fine.
I've put for now a R1of 6,8M and R2 of 10M, and i have about 3Vpp on R2. The big problem of this is that i didn't unsdertand why that values give me the 3Vpp.
Btw, if you thing the capacitor voltage divider is better, i sure use that strategy.
thanks
angelo