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Old Jan 20, 2009, 09:06 PM
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2.4Ghz radios? How do you get signal to a sub?!

Hi guys!

I'm one of those migrants from the heli forums. Please don't throw rocks!

I have a sort of... custom submersible plan for some underwater cinematography. This is going to basically be a sort of underwater inspection unit, with remote video capabilities.

What I'm wondering is what kind of radios you guys use and what the range is for them. I'd like to go wireless but I'm not sure if its going to be all that feasable.

Does the air to water transition kill the signal distance? Is the 2.4Ghz spread spectrum a no go? Range? Bueler?

-Tyler
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Old Jan 20, 2009, 09:09 PM
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Do a search around this forum as your question has been asked often.

As you will soon find, lower frequency the better, so 2.4 GHz will probably get you a few inches in fresh water. Other frequencies around the 72/75 MHz range will get you adequate range, depending on where you run your sub and the angle between your transmitter and submarine location in the water.
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Old Jan 20, 2009, 10:14 PM
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Thats right 2.4 will not work at all and is eleagal to boot for serface use.

An old AM raadio I have does beter in depth in water reception than a modern FM PCM radio but very close.
so go with a 75 meg. computer radio like the Futaba 9 CAP just get the reciever and module on 75 meg. or not I use both air and ground,no diference,Im sure you have a good heli radio ,that works just fine.
Most of the normal boat radios dont have computerization and are overpriced.

I have used them all for years now and fly helis also but subs and ROVs are my pastion.

Just remember one very important fact,the chemical make up of the water is critical for radio transmition,the more clorine,sulfur,iron ect the worse and especialy salt ,never run in the ocean or brackish water unless you dont intend on going below the length of an extendid reciever antena! It will not recieve signal.

PCM works very well with the abundant failsafe capabilities,my favorite and well tested format ,rock solid underwater reception.


Dave
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Old Jan 20, 2009, 10:17 PM
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Dave,

This is very useful information for me.

I am planning on SALTWATER.

Generally, what kind of range do you get? Is a lot of the loss due to refraction from the water? Could I drop a radio lead into the water to increase reception?

Thanks for all the help so far. This is greatly influencing my ideas about how to go about completing my task.
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Old Jan 20, 2009, 10:33 PM
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Great, No an antena in the water makes no diference the salt in the ocean is just to abundant for these radios,you would need a tethered control and vedeo system just like ROVs have they have spent millons trying to do the above wirrelesly and not even the military as far as I know have a reliable system .....yet.

Now in fresh water no problem water I get about 25 ft in the spring waters here in Florida the cleanest water in the world ,I can go all the way down in Gennie Springs and still have control about 25 ft. I have not gone deeper except in Lake Tahuo about 65 ft! thats deep for a RC sub and I useda an old Futaba 4 chanel AM radio and a fish finder on a boat.

Needles to say the sub did not implode I still have her,my first.

Refraction ,water quality and radio strenght and type all make a huge difference in RC Subs.

Dave Amur Ship yard
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Old Jan 20, 2009, 11:11 PM
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Great pictures!

I can see the shortcomings of radio signals for the depths. I am wondering if perhaps an infrared or ultrasonic system might work. Clearly beyond my capabilities, but interesting to ponder. The response time would probably be pretty bad.

We'll have to go with a teathered setup for sure. 25ft would probably be the minimum we would require. Sending wireless video would probably prove difficult as well.
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Old Jan 21, 2009, 06:50 AM
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Correct the vedeo signal does not penetrate the water ,salt or fresh.

Dave
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Old Jan 21, 2009, 07:10 AM
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Quote:
Originally Posted by aquadeep
Thats right 2.4 will not work at all and is eleagal to boot for serface use.

An old AM raadio I have does beter in depth in water reception than a modern FM PCM radio but very close.
so go with a 75 meg. computer radio like the Futaba 9 CAP just get the reciever and module on 75 meg. or not I use both air and ground,no diference,Im sure you have a good heli radio ,that works just fine.
Most of the normal boat radios dont have computerization and are overpriced.

I have used them all for years now and fly helis also but subs and ROVs are my pastion.

Just remember one very important fact,the chemical make up of the water is critical for radio transmition,the more clorine,sulfur,iron ect the worse and especialy salt ,never run in the ocean or brackish water unless you dont intend on going below the length of an extendid reciever antena! It will not recieve signal.

PCM works very well with the abundant failsafe capabilities,my favorite and well tested format ,rock solid underwater reception.


Dave
I'm pretty sure 2.4GHz can be lawfully used for all R/C vehicles, surface or aircraft.
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Old Jan 21, 2009, 07:22 AM
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2.4 is legal for ground or air.
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Old Jan 21, 2009, 10:37 AM
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Hi
I have built RoV,s using a standard 40 Mhz radio set with no mods made to the Transmitter.
The receiver has the aerial removed and a wire inside the umbilical cable attached that ends on the surface with a normal aerial soldered on the end.
This has been good to 60 meters in sea water for me.
Basically you are extending the receiver aerial.
I have no idea if your radio would work in this application.

Regards Antony(UK)
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Old Jan 21, 2009, 11:20 AM
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Yes it should work fine will try it! Thank you

I forgot that cars use the 2.4 range,but still the freq. will not penitrate the water well.

Dave
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Old Jan 21, 2009, 11:31 AM
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Quote:
Originally Posted by aquadeep
Thats right 2.4 will not work at all and is eleagal to boot for serface use.

Dave
2.4 GHz is perfectly legal for surface use models, as well as aircreaft - think of it as 27 MHz on steroids. Bachmann (the model railroad company) made the very first Spectrum units for Digital Command Control of model trains. The very first Spektrum units were sold as pistol grip units or modules for pistol grip radios for the rc car crowd back in 2004. Spektrum is a registered trademark of Bachmann.
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Old Jan 22, 2009, 03:51 AM
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Hi Rhetor,

I had to laugh when reading your thread, I am also a heli guy, and I have been doing some aerial photography with my helis, and the next thing I'm looking at doing is making up a rc sub with onboard camera.

I would propose the only way to do so would be to have the receiver aerials (both control and video downlink) run from a buoy that the sub is tethered to. I doubt most underwater inspection/hull inspection etc. jobs would require more than 25ft depth.

Could you share you design? I would be pretty interested to see how others have approached the problem. I have a local hobby shop selling the Thunder Tiger "yellow" subs, I was going to run one of those, minus the body, with thrusters retrofitted for maneuverability.

Anyway, good luck!

Ben
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Old Jan 22, 2009, 06:38 AM
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Hi Ben,

I don't think I can post my design, but I may be able to post pictures when it is completed.

The floating buoy was an idea we had, we are wondering whether or not to just switch to a full teathered system though. I think I would prefer the buoy.

-Tyler
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Old Jan 22, 2009, 08:10 AM
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Hi Rhetor,

With a static diving sub you can always do with an emergency flotation. I was going to make the tether retractable because A) less cable drifting around getting caught on things and B) I may perhaps be feeling too lazy to pull the sub up in the event of a failure.

I was thinking of using high capacity fishing line with the aerials bundled with it.
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