In Reply to: 8-channel RF transmitter-receiver posted by janet on 02/07/03 at 11:44 AM:
The U.S. Navy communicates with submarines using very low frequency RF signals, about 10kHz. I don't know how much power you would need, and if the transmitting antenna were in the water results might be better. It would be more straight forward to have a surface float with wire connection to the submersable and an antenna in the air. In any case, I recomment using subcarriers to carry the up, down, right, left, forward, and reverse data. With a carrier of 10kHz you could have subcarriers at 100, 150, 200, 250, 300, 350, 400, and 450 Hz. A phase lock loop filter will seperate the subcarriers and pulse width modulation of the subcarrier can be used for control.
If you use the float idea with the antenna in air, you could use a CB radio transmitter on one of the radio control channels. Capture of the signal will be easier because the modulation is a small part of the frequency spectrum. You will have to purchase a radio control transmitter or modify a voice CB transmitter because the regular voice transmitters skip over the R/C channels. The channel frequencies are listed at the FCC website.