The schematic
Any tubes..any transformers that comes from an old radio can be used in this transmitter..its not critical.
The coil can be made by any wire..no need for litze...a calculator (
http://www.pronine.ca/coilcal.htm ) allow you to make the coil as you like...the feed back is one forth of the turns. I am not saying this is the ultimate transmitter...however the sound is great...depending of the OPT (T1). Don't worry about the OPT impedance as its not connectet to a loudspeaker...however you can connect a loudspeaker as a controle monitor..but use a resistor least 27 ohm or its going to be loud.
Range...some hundred meters...definitely not legal.
Voltage before 'L3' approx 200V...just like an *old radio*...ATT. R13 180ohm or less,C11-12...2,2nF 600V
The magic eye and the mic is only an option....over-modulaton causes sparks in the tuning-capacitor...just like a real transmitter.
In spite of its simplicity it makes no noticeable FM modulation...