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Old Nov 07, 2013, 11:20 AM
Guard-Officer is offline
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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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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.)
Old Nov 15, 2013, 10:46 AM
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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.
Old Dec 12, 2013, 10:34 AM
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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
Old Dec 12, 2013, 02:16 PM
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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
Old Dec 13, 2013, 09:26 PM
nick_75au is online now
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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
Old Dec 15, 2013, 12:08 AM
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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!
Old Sep 16, 2015, 08:16 PM
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2.4GHz Submarine; Salt Water


One solution is to use a tether to a bouy.

A thin coax cable leading the 2.4GHz signal up to a bouy which would house the normal antenna in an elevated waterproof column (PVC for example).
Match the cable and antenna inpeadances correctly and you're good.

Then the transmitter and reciever wouldn't know the difference.

For depths greater than 10ft, a signal booster would be needed.

Can anyone say FPV ROV!?
Old Sep 16, 2015, 08:46 PM
sunworksco is offline
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It is possible to add a 75MHz transceiver to the radio....
Old Sep 18, 2015, 05:27 AM
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Yo


Just run at a foot deep ,

use a 1 foot long antenna, that loses signal when you dive the antenna all the way under ,

and fail safes

to surface the boat
Old May 31, 2016, 01:55 AM
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would 2.4 ghz work if the Reciever antennae was extended so that it could be attached to a bobber, the Antennae would unravel as the sub dived and the bobber with the attennae sticking out the top of it above the surface would remain on the surface?
Old May 31, 2016, 09:21 AM
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You can't extend a 2.4 antenna. That short stub (or two) is tuned to the Rx. You'd have to have the entire RX in the bobber and feed to servo leads down from that, not practical for obvious reasons.
Old May 31, 2016, 11:13 AM
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Submarines, etc.
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Originally Posted by Kenwhite23 View Post
would 2.4 ghz work if the Reciever antennae was extended so that it could be attached to a bobber, the Antennae would unravel as the sub dived and the bobber with the attennae sticking out the top of it above the surface would remain on the surface?

the EFFECTIVE part of a 2.4ghz antenna is the short 1.25" portion at the tip that isn't insulated.

the easiest and cheapest way to get your antenna up out of the submarine would be to buy a "specialty" antenna made for carbon fiber model airplanes... something like this:

https://alofthobbies.com/600mm-recei...nna-frsky.html

and extend the antenna out the top of the sub far enough that it can reach the surface... use a 1/8" plastic tube like the old r/c cars

this is basically what the "olden" 75mhz radio operators did when they ran their submarines in salt water. nothing penetrates salt water, so... make the antenna long enough to reach the surface when you are submerged, and then you continue to have reception. at the loss of scale appearance, or, more importantly, the inability to dive deeper than the length of your antenna.
Last edited by tsenecal; May 31, 2016 at 11:50 AM.
Old Jul 30, 2016, 01:34 AM
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is a problem the tx for subs, futaba as far i know is the only who is making radio than can works in subs, but the problem is that is only 4 channels, the only way is that those who know about radio and electronics gather and develop a "diy" radio, i had researched a litte and theres some ic like lm1871 and lm1872 , but its channel fixed, so its a problem anyway, also i found this page that had the circuit of an old radio
http://www.norcim-rc.club/Radio3.htm

the only problem is that i dont know to much of radio im good only with digital electronics, and the people that i know they understand radio they dont explain to me too much, i feal that is kinda complicated to understand circuit, and the other problem is that uses rf chokes toko with a numeration that no longer exist, so i couldnt know what modern replacement could be
Old Jul 31, 2016, 05:46 PM
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This topic come up every couple of years and is chewed over again and again.
The gents that discovered/developed/engineered model subs several decades ago pointed out then, and it is still true today, that if one wants to run subs ( UAV's and tethered craft exclude) then one needs to use the lowest frequency radio, available on the market. That does not mean it has to be fancy, nor a computer radio.
If one looks hard enough one can find 27 mhz and 75 mhz radios, new and used.
2.4ghz DOES NOT,WILL NOT, WORK. If one can not or will not pay for a 27 or 75 mhz radio, than one can not afford to run subs.


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