>On Wed, 4 Mar 1998 21:57:31 -0000 Andy Shaw >writes: >>Hi Folks, >>I'm sure one of you out there will know the answer to this one. >> >>Anyone any idea how well a 1.3GHz radio transmission will penetrate >>fresh >>water. I build model subs and I know that standard 40MHz Radio control >>gear >>works well down to ten feet or so. > Mike Keitz wrote: >I don't think it would work very well. The higher the frequency is, the >more the water will attenuate it. So the navy uses VLF to transmit to >their subs. > >You may be able to control the sub over several hundred feet using some >sort of modulated sonar, but getting a TV image back is almost certainly >going to require a cable. > How about a resonant periscope, 1.3 Ghz is 23cm so a quarter wave will be around 4-5 cm, the water would make a nice ground plane and you could tune for minimum vswr by diving a little. :-) Ray Gardiner (DSP Systems) ray@dsp-systems.com http://www.dsp-systems.com private email to:- ray@netspace.net.au