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R/C Submarine modelers

Postby 80-1054718141 » Wed Jun 04, 2003 5:25 am

Well I am a computer man, not an RC man, but was wondering what some more experienced modelers say about transmitting from underwater (thinking about just a pool type thing). I was thinking about using a 2.4ghz WiFi, not someone said thats the natural resonance freq of water. I was wondering how well that would work?

Range is not an issue because this is for my pool only, and I can mount the access point near above on or hanging from the cage. So I would say I need 10ft max.

Also wondering if any kits come with a clear dome where I can mount the camera or would I have to fabricate that myself?
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Postby KOEZE » Wed Jun 04, 2003 5:41 am

Range would be at or around 0 ft. AFAIK 2.4 ghz is the same frequency af amicrowave oven so the only thing you would do is boil water (and not very fast either :laugh: ) You could try a 900 mhz transmitter (lower is better) to improve the range.

I have read a comment somewhere that the only relyable way of transmitting video from a sub is via an antenna at the surface. (Buoy or long antenna sticking out of the water)

EJK
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you get older because you stop playing.
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Postby 80-1054718141 » Thu Jun 05, 2003 8:53 pm

I venture to guess that 5.4ghz won't work either? Hmm guess I will have to look into a lower freq solution.
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Postby Ramius-II » Fri Jun 06, 2003 2:47 pm

Dear PPGMD:
In the 1.2 GHz range with a power of 800 mw you should be good to a depth of 18 inches. This is according to Ramesh who has been experimenting with video. You can get transmitters up to 3 watts and they get expensive (around $500.00 for the transmitter and receiver). A amature radio friend (W1NMZ) does RF work for the military and we have discussed the problems at lenght. 2.4 GHz is the resonant frequency of water and therefore the water will absorb the signal like a sponge. At 2.4 GHz you can achieve a depth of 3". :(
I feel there are two areas that should be addressed, both have to do with the antenna system. An antenna can provide gain like an amplifier and we usually talk in terms of DB (decibel) gain. Antenna's without "tuned" (correct lenght) elements (the driven element and the reflector element) will typically produce negative gain. That is part of the power you put in is waisted. Whip or single wire antenna's are this type. As far as I can see, the best choice for our application is a "coaxial" antenna. The guys with R/C helicopters swear by them as well as the turnstile type.
Next is the receiving antenna where we don't have a "size" limitation. Receiving antenna's at 1.2 GHz are not very large and produce over 10 DB of gain. Since I don't know if this means anything to you, every 3 DB is twice the power. Thus, 2 watts with 3 DB of gain is equivelent to 4 watts and 6 DB would be 8 watts. :D
Hope all this is of some help. :)

Ed (AKA WB6NSN)
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