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Jan 06, 2016, 09:18 PM
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Question

Can 2.4 Fly Sky signals penetrate deep enough at a distance of 50 ' ?


Another modeler says no.

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Jan 06, 2016, 09:49 PM
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I'm pretty sure everybody will say NO.
Jan 06, 2016, 09:55 PM
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ausf's Avatar
My 2.4 Spektrum consistently lost signal as soon as it went underwater, no matter how close to the dock.

I tested it in a bucket, receiver in one hand, Tx in the other and it blacked out about 3 inches down.
Jan 06, 2016, 10:24 PM
KC8WPF
CG Bob's Avatar
The very first link in the "START HERE" sticky at the top of this discussion board is : 2.4 underwater.
Jan 07, 2016, 08:42 AM
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Thanks submariners.
No higher than my old 70 meg gang will be used.

Rich
Jan 07, 2016, 09:36 AM
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One solution for the problem of not having many 75 MHz radios available is to look at radio's on Ebay. There are a ton of them available at 72 MHz and a few on 75 MHz. The 72 MHz units are not legal in the U.S. for surface use, but they can be sent to Radio South to be retuned to 75 MHz. It's a little convoluted, but is a workable way to get radios that will function underwater.
As several folks have already stated, 2.4 is most definitely of zero use on anything that isn't on the surface.

Chuck
Jan 07, 2016, 10:05 AM
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We could just go to under 100 K hz modulated signals for all the channels. Skip using R F entirely.

Noise travels great under water.
Jan 07, 2016, 02:05 PM
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Quote:
Originally Posted by cyclops2
We could just go to under 100 K hz modulated signals for all the channels. Skip using R F entirely.

Noise travels great under water.
I maintained a LORAN system that transmitted at 100 KHz. Going there would present problems with your Tx antenna. The one I used was 400 foot tall while the Coast Guard systems were typically 625 foot.
Jan 07, 2016, 02:27 PM
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You guys are TOUGH !!

Lets just use a sound transducer......SONAR. Heck. We are submarine captains. Pizoelectric transducers suspended in the water would do fine. Leave out all the R F stuff.

NO licenses needed. Very low power also.
Jan 07, 2016, 07:11 PM
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Quote:
Originally Posted by cyclops2
You guys are TOUGH !!

Lets just use a sound transducer......SONAR. Heck. We are submarine captains. Pizoelectric transducers suspended in the water would do fine. Leave out all the R F stuff.

NO licenses needed. Very low power also.
LOL, i am thinking of this scene and Sean Connery calmly giving your RC sub the command to dive with "one ping only"

With voice recognition software, we can just tell our subs what to do. Devise some kind of underwater bullhorn.



"One Ping Only" (0 min 23 sec)
Jan 07, 2016, 08:34 PM
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ausf's Avatar
Sound travels 4 times faster underwater than in air. Further too.

It moves so fast, your brain can't tell direction like it can on the surface. If you've ever been diving, you'll hear a constant white noise, which is actually everything from close sealife to ship traffic miles away.

If there was a way to direct via voice command, water would be a perfect vehicle for it.
Jan 08, 2016, 08:19 AM
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We have ZEE technology. But there may not be a payback in a lifetime.
Jan 08, 2016, 10:07 AM
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Quote:
Originally Posted by cyclops2
You guys are TOUGH !!

Lets just use a sound transducer......SONAR. Heck. We are submarine captains. Pizoelectric transducers suspended in the water would do fine. Leave out all the R F stuff.

NO licenses needed. Very low power also.
Problem is, the lower the frequency (and sound is nothing more than a frequency our ears can detect) the lower the data rate. IOW, at the freqs of sound, you might get better results just shouting at the thing.

The Navy had a system (maybe still do) for communicating with submerged subs called ELF or Extremely Low Frequency. It transmitted at something like 100 Hz if I remember correctly. They would use a 1500 mile length of electrical high tension power line as an antenna and it would literally thump the ground. But data rate was measured in bits per minute. And it took so long to get a message through, they used three letter codes to identify pre-defined messages for the sub. Even so, it could take 15 minutes for one of those codes.

So, by the time you get the message to your sub to look out for that rock on the bottom................................
Jan 08, 2016, 10:18 AM
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All old really old guys !!!


Remember the PW PR Galloping Ghost controls ? Today it is very simple & accurate to transmit sound waves in water that way. 2 or 3 tones equals 4 or 6 channels of control. 15, 20 or 30 kilocycles.


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