--0__=85256A85004B5B848f9e8a93df938690918c85256A85004B5B84 Content-type: text/plain; charset=us-ascii In college I built a sub using depth finder transducers to communicate acoustically... we never found the limit of the range (pond was too little). We at least had 500'. Will this approach work for you? As for RF, one must remember that the wavelength changes as you travel through different mediums. So it will be necessary to adjust receiver antenna length. The other factor is that water 12" thick (ie human body model) attenuates 400mhz by 20db. Not sure of the frequency effect, but would expect about 10dB attenuation per foot of water at 100mhz (a guess). Knowing this you can calculate xmtr power based on a particular receiver/antenna sensitivity. Also, magnetic fields are uneffected by water... you may have better luck (less attenuation) dealing with the magnetic field component instead of primarily the electric field component. Scott O'Reilly John E NORC To: PICLIST@MITVMA.MIT.EDU Subject: Re: [EE]: Underwater RF Sent by: pic microcontroller discussion list 07/09/01 05:54 PM Please respond to pic microcontroller discussion list RC Subs are good to about 10 feet in really clean water. I'd like to go deeper than that. Thanks John -----Original Message----- From: Scott F. Touchton [mailto:Scott.Touchton@US.JDSUNIPHASE.COM] Sent: Monday, July 09, 2001 2:39 PM To: PICLIST@MITVMA.MIT.EDU Subject: Re: [EE]: Underwater RF Check out radio controlled subs... they seem to get a hundred feet or more with about 100mW @ 75mhz (out, not down!) ; ) Scott F. Touchton 1550 Engineering Manager JDS Uniphase O'Reilly John E NORC To: PICLIST@MITVMA.MIT.EDU Subject: [EE]: Underwater RF Sent by: pic microcontroller discussion list 07/09/01 05:35 PM Please respond to pic microcontroller discussion list Has anyone ever tried transmitting from above water to underwater and vice versa? I am thinking of using 2m amateur transceivers on either end, and I'm wondering what kind of range I can get with a couple of watts. Also, if I put one half of the antenna (either ground or radiator) in the water, will that make a difference? TIA John -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body -- http://www.piclist.com#nomail Going offline? 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