Robert Rolf wrote:
>>>>If we ran a wire from the transmitter antenna through an air line that
>>>>has to go to the underwater unit and connected it to the receiver
>>>>antenna, would that work?
>>
>>
>> You'd actually have to attenuate the signal significantly, and it
>> would be best to use shielded cable, but YES, this will work.
>
> Actually, it would depend on the kind of water (fresh vs salt),
> and on the radio frequency in use.
> Salt water, and high frequency (2.4Ghz is now used in many sets)
> and you won't get far, even with a wire. I doubt that you can do
> 300M even at 72Mhz (common R/C band in the US) with just a bare wire.
> The loading from salt water is HUGE.
>
> I would suggest using COAX so that you have a controlled impedance path
> to the receiver, and then yes, it will work. But I agree that you will
> probably need an antenuator to not overload the RX.
> If you need it thin, RG174 coax is about 1/8" diameter and not too lossy
> at 72Mhz.

If the OP is willing to run coax... why bother with RF at all? Why not run a 
well insulated cable with however many pairs the OP needs to control this 
thing?

Perhaps we need to better understand the application?

Vitaliy 

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