So,

Batteries for the filament aren't needed anymore for the new MOPA, the master oscillator and power amplifier. The whole circuit board can be placed in the casing of the original scratch built tube radio.

I didn't see this before but it was worth to try. There are tubes that need 12.6 V filament tension, so, when supplying my convertor with 12 VDC why not use such a radiotube , double triode, with that kind of filament for 12 VDC??

On the photograph is shown all what is needed to make the carriër wave, only needed a 12 V battery to supply and the transistor tone generator (,or two of these).
All small components are mounted on bottom site of the board, capacitors, chokes, resistors.
The efficiëncy of the converter is +80 %, so for 10 mA at 100 VDC a current of 100 mA of the battery is needed, added the current needed for heating of the tube,(filament) 150 mA, makes 250 mA, the grid modulation of the PA (?) is efficiënt and together with the tone generator another 10 mA is needed, makes total 260 mA. at 12 VDC.

BTW this tube was not designed for supply by a battery but for me it does a good job! It looks like 100 VDC is enough for the needed output power but, If I want I can go to 300VDC with this tube.

TF.