TV Transmitter with Audio
The Audio section
(1)Coil: The most difficult point is the coil. You can use any type of coil as long as it fits the inductance. But the size of coil for 4.5 MHz is quite large if you use usual type of coils. Here I will use Ferrite Troidal core that is made by Amidon Associates.
Wind 0.2 ECW (enamel-coated wire) around the “FT-50-43” (Amidon) in 24 turns.
You can use popular ones such as 2SC2001, 2SC1815, 2SC1907, etc. But you must keep the pins (E, C, B).
How to adjust:
Connecting the prove of the frequency counter at “#to the audio-in”. Then adjust “Trimer cap. (80PF)” as the frequency counter shows exactly 4.5MHz. Sometimes, you have to add some capacitors (depending 100-1000PF) at the “E(mitter)” position of the transistor in order to adjust the frequency.