In Reply to: low frequency rf power amp posted by Joel on 04/27/03 at 10:00 PM:
What are you using for a reciever? That will determine how much power you need. The big problem will be getting power radiated at such a low frequency. A quarter wavelenght at 30kHz is 40,000 meters so your antenna will be a very short one even if you make it 10 meters long. Almost any transistor could transmit 10 meters if the frequency was higher. The US navy transmits to submarines using low frequency but the antenna covers many acres and I suspect the power is in the megawatts.
You could make it work with a very sensitive receiver: use an AM radio with a low power oscillator nearby at 600 Khz. You should be able to pick up the 30kHz transmitter at 570 kHz and 630 kHz.
Any TO-220 NPN will work at that frequency. For the antenna, try a large (physically large) inductor with a flat plate on top (several square feet) and a similar plate on the bottom. Compute the capacitance of the two plates and the inductance needed to resonate.
I will be interested in knowing how it works!