I agree that he can get more voltage swing from a collector tank. I also did a little research on short wire antennas, and found that they look like small capacitances, which means that more tank voltage means more radiated power (true in any case, but really important for short antennas).audioguru said:MStechca's transmitter has its tank as its emitter to ground resistor. Therefore the antenna can't have a voltage swing that is much higher than the supply voltage which results in a high RF power output as occurs when the antenna is connected to the transistor's collector.
Also, the tank is trying to be a high impedance parallel-tuned circuit, but it is in a low impedance emitter circuit so the frequency stability of the oscillator is probably very poor.
I have been simulating a (center) tapped inductor in the tank (in the collector circuit), and can get, as you would expect, more voltage across the tank than is possible with an untapped inductor. A side benefit seems to be lower harmonic generation. It appears the inductors can be either mutually coupled or not. If they are not, you need the same total inductance. If they are coupled, the self-inductance can be less, because the coupling adds to the inductance.
I don't think this will work for a properly tuned antenna, because it will look like a low resistance load, killing the Q of the tank.