hi
I have just found this article here,but maybe it's to late.looking at the schematic diagram it used T1 transformer it's design for a 50 ohm output,with 1 to 2 turns ratio .so the reflected impedance is 12,5 ohms.
The way I think the primary inductance and C4 must have the value to be resonat at the frequency it is operated .
Even it 's a broadband transmitter ,it has it limitation ,moving to medium wave,I believed You must change the Inductance value of T1 with a bigger Ferrite maybe and change the value of C so the reactance of C is 12,5 ohm at the frequency it used ,and also the reactance of the inductance.
If You used it in the medium wave transmitter,that used a fixed frequency .Something comes into my mind ,Why don't we used and parallel resonant circuit,with uses air wound coils,
since the Inductance is Small ,we can used a small coil,and C in parallel with it,
That resonate at the Frequency .
Is it a possibilitly?
Just a though
