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Old Nov 07, 2013, 11:20 AM
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Canada, ON, Quinte West
Joined Feb 2009
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The propagation of radio waves through water is not the problem, its the propagation of radio waves through the surface of the water that is a major problem. your range is so limited because you loose a significant amount of the signal and its strength when it bounces off the surface of the water. The ultimate solution would be to have instead of an antenna, a transmitter buoy with an umbilical up to your transmitter in your hands. then the radio wave is being generated under the water already and there is no need to penetrate the waters surface. The same holds true for your submarine, if you mount the antenna on the exterior of the hull, the transmitted waves do not have to enter the air filled compartment of the submarine, which would further reflect the waves. as an experiment, put a transmitter in a water proof bag and use it under water (obviously a cheap transmitter...) I would bet that if the entire antenna were submerged, with no air around it, you would have pretty great signal back and forth. I believe you can get frequency modules, if you run wires from the transmitter to the module under water and generate the frequency there, you would have great success.

But keep in mind this is just a theory.

Good Luck!

Cheers
G-O
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Old Nov 14, 2013, 09:52 PM
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Joined Apr 2012
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It may not be legal, but 72 works underwater fine. When I lived in L.A. a guy I knew out there had a sub he ran in a local park lake using a 72 aircraft radio. No problems. (Hopefully he didn`t shoot anybody down in the area.)
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Old Nov 15, 2013, 10:46 AM
Man from Atlantis
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London
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I don't think it's just the radio bouncing off the water surface, UHF just doesn't propagate through water very well.

I guess it' a bit like wading through water, take it slow, and you get along okay, start trying to run, and you fall flat on your face.
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Old Dec 12, 2013, 10:34 AM
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United States, AZ, Queen Creek
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The lower the frequency, the better the RF penetrates water. The US Navy uses very long waves to communicate with their submarines. I would think 27MHZ would be better than 72
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Old Dec 12, 2013, 02:16 PM
Michigan, USA
Roedj's Avatar
Joined Apr 2008
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Quote:
Originally Posted by Sub culture View Post
I don't think it's just the radio bouncing off the water surface, UHF just doesn't propagate through water very well.

I guess it' a bit like wading through water, take it slow, and you get along okay, start trying to run, and you fall flat on your face.
You're right.

There are three sources of signal strength for RC subs:

1) Transmitter antenna to surface of water (loss in air),
2) Signal going from air to water (surface of the water), and
3) Signal loss through the water.

All three makes it darn near a miracle that this works at all at 75MHz, let alone 2.4GHz - 2400MHz, but the greatest individual loss is #2 - going from air to water.

Dan
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Old Dec 13, 2013, 09:26 PM
NeverAgainVolunteerYourse lf
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Australia, QLD, Regents Park
Joined Mar 2007
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Quote:
Originally Posted by dirtybird View Post
The lower the frequency, the better the RF penetrates water. The US Navy uses very long waves to communicate with their submarines. I would think 27MHZ would be better than 72
The difference is negligable between the various R/C Mhz frequencies.

The Navy uses Khz range signals transmitted at 1 Mega watt or more, , takes 30 seconds for 1 character to be transmitted, though it does have 10000 Klm range basically calls the sub to antenna depth to receive the full message. I visited the trannsmitting station in Exmouth

http://en.wikipedia.org/wiki/Naval_C...Harold_E._Holt

I think this might be somewhat out of the scope of what we want to do LOL
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Old Dec 15, 2013, 12:08 AM
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Joined Mar 2010
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Originally Posted by nick_75au View Post
The difference is negligable between the various R/C Mhz frequencies.

The Navy uses Khz range signals transmitted at 1 Mega watt or more, , takes 30 seconds for 1 character to be transmitted, though it does have 10000 Klm range basically calls the sub to antenna depth to receive the full message. I visited the trannsmitting station in Exmouth

http://en.wikipedia.org/wiki/Naval_C...Harold_E._Holt

I think this might be somewhat out of the scope of what we want to do LOL
Come on mate, don't be defeatist Sure it might be more of a club rather than individual project, but never underestimate the resourcefulness of an RC modeller!
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