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DEEP WATER: Transmission?

Old 03-02-2004, 10:53 AM
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///samson
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Default DEEP WATER: Transmission?

Does anyone know if UHF/TV signal will transmit through water? or know the science behind it?

I have a wireless camera,,, and I often dream of making my own container to drop it to the bottom of Green Lake - in Green Lake, Wisconsin (237 feet deep at the deepest point).

Thanks in advanced.

Old 03-02-2004, 11:05 AM
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Rj-TailSpin
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Default RE: DEEP WATER: Transmission?

So you think that water is clear enough... hehe. I live 30 minutes from Green Lake. There's no light underwater so you would need an IR camera with IR leds to see anything. Radio waves travel nicely through air... but water mmm I haven't tried that one yet. Let me know when you perform your test and I fly high above and capture you while you stare at a black screen LOL Just kidding. It sounds like a fun project. Let me know when you going down there... no pun intended hehe
Rob
Old 03-02-2004, 11:43 AM
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///samson
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Default RE: DEEP WATER: Transmission?

Hey bud - Well, I have looked into the 'IR' Cams you can get at any Gander Mountain store and local fishing shops,,,,but the quality of the images is rather dull.... So, being a gear head, I want to fabricate my own with Radio Shack LEDs etc!!!

Green lake IS a very very dark down deep. I skin dive in Norwegian Bay to a maximum depth of about 50 feet and everything starts to fade - even the rock bass don't go down that far. Directly out from our place on Sugar loaf sits the 237ft section and we often wonder what would be at that depth. .. . . maybe some of the Ojibwe tossed some relics down there hundreds of years ago....or the famous wooden boat that sank during a storm, but most likely bikini tops, fishing poles, and beer cans rest untouched at that depth. Either way it would be a fun project. [8D]
Old 03-02-2004, 11:58 AM
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Default RE: DEEP WATER: Transmission?

at that depth you would need a pretty strong case as the pressure is extreamly strong that deep. It would take a professional camera that deep. Light doesn't go that far down either. There isn't anything you will see either. At that depth the silt is so thick it covers everything. I used to scuba dive a lot so I understand the pressure part of it.
Old 03-02-2004, 12:18 PM
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///samson
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Default RE: DEEP WATER: Transmission?

Exactly - I've got the pressure covered. By using small PVC tubing injected with silicone glue to remove all available air pockets - thus making it denser than water, I was able to sink it to 200ft with no leaks or ruptures.
Old 03-02-2004, 04:14 PM
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Default RE: DEEP WATER: Transmission?

I would forget about wireless... just run a wire down with an off-shore rig. This way we could putt around to find stuff. Let's not forget the claw to bring objects back up. I have been planning on using my VidFly to capture movies of our jetboat as seen here: http://www.network54.com/Forum/Hide/143168 I just haven't had enough gutz to do it! This Spring, the SpeedSter will be dubbed an Aircraft Carrier-grin. I hope it works! Let me know when you want to dive your PVC invention, I'll bring the floating ground station for viewing!
Rob
Old 03-03-2004, 02:39 AM
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lvspark
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Default RE: DEEP WATER: Transmission?

I've got a water proof camera with IR LED's..... Metal case, o-ring seals, etc... I do not know the depth rating tho?
I'll read up on it and get back to ya.. Sounds like fun!
Old 03-03-2004, 09:29 AM
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///samson
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Default RE: DEEP WATER: Transmission?

I'll def. try a wired camera at some point -- but first I want to know if my 1.2ghz wireless cam will transmit through water (perhaps with a submerged antenna).

Anyone?
Old 03-03-2004, 10:32 AM
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Rj-TailSpin
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Default RE: DEEP WATER: Transmission?

That's a tough one to answer. Frankly, I never thought about it. I do know radio waves travel great on dry, less humid days. When it rains or snows... well established RF links die. I would guess radio waves will not travel well through water without massive power and then they would only travel a short distance. Sub's use ELF which uses extremely low frequencies for underwater communication which travels through the earth back to a little town in Northern Wisconsin. Without it, the subs can not communicate while under water. As a matter of fact, I remember a power outtage occurred in that area and the military couldn't communicate to the subs. Their orders are to assume the US is gone or under attack, and get ready for a fight. Quite a serious situation all because someone knocked down a power pole. I think that weakness has been fixed... at least I hope it has!

In order for radio transmissions to carry a modulated video signal... a good bit of data or bandwidth is required. Radio encoding and decoding depends on timing. When air is saturated, radio waves travel slower. This change in propagational speed corrupts the ability to decode the video signal. The speed at which a radio waves travels through a media is called the velocity constant. In water, the timing would be all messed up because the devices are made to work with the velocity constant of radio waves traveling through air.

I guess, I worked through this one. The answer is NO, wireless video transmitters will not work under water. That doesn't mean you shouldn't give it a try-grin. I would have the wired rig available because I think the wireless testing will be short lived.

Wire idea??? mmmm A wire which will handle power and video, and still be able to sink. Perhaps you should purchase a wooden spool of wire and put a handle on it to reel it up. Remember, electrical signals travel on the skin of the wire and they to will be affected by water. The velocity constant and the impedance of the wire will change if it gets wet. Phone companies deal with this problem constantly. The wire will need to be water tight. This might not be easy with the water pressure at 200 plus feet down.

I believe it can be done with a hard-wired camera. However, most underwater cameras you buy on the market, only go 25' and some more. Perhaps it's not easy to do. Nevertheless, I think it sounds like a fun project nonetheless!

Rob
Old 03-03-2004, 03:11 PM
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///samson
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Default RE: DEEP WATER: Transmission?

My first concern with an extra long wire was loss of clarity due to the decrease in a healthy current over the long distance. I want to use a 'mini-camera' with lead (or UHF transmission) back up to the surface of the water to connect to a recording device - simply because you can make a very water tight container a lot easier for a smaller device. However, it might make more sense to encase my Canon Elura pictured below - and run a lead to either a laptop or simpe LCD. That way the camera can record on-spot images with complete clarity - and the transmission would be (hopefully) just clear enough to swing/navigate it on the bottom of the lake.

You're totally right about tranmission through water. It makes complete sense now. I might just make a wire-less boat camera like they had on the old 'Flipper' shows -- so they could watch what was below the boat.


But am I right though??? Doesn't looking at the bottom of a 237ft deep lake just sound like a mini mission to Mars?

Old 03-03-2004, 03:58 PM
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Default RE: DEEP WATER: Transmission?

Until YESTERDAY, the Mars mission has consisted of press reports of how far the rover rolled, when it stoped, when it moved an appliance, when it napped... I was so sick of the press releases which could quite easily been the same if the rovers were here on earth... And, I am so sick of listening to the garbage of "what song" the rover woke to!!! It might be tradition, but it keep internal please! I wrote them a nasty email last week to tell them to start giving us some real science instead of all this junk! 800million and it rolls, naps, etc... I think they might have listened to me because yesterday was the first concrete mention of any science findings. I want the science!!!

Yes, viewing the bottom of the lake would be great! Just think what treasures might be down there! I think it would be fun. 235' isn't very long for a feed line. What might work is use a straight wire as antenna and connect the TX and RX to it. I would have to think about this alittle, but it would allow for the RF to propagate on the wire. A fixed length of wire could be used as the media. There are cables for every application. If you have deep pockets... no problem finding a solution!

Rob
Old 03-03-2004, 04:29 PM
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Strykaas
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Default RE: DEEP WATER: Transmission?

That's a very interesting project.

I would start by taking photographs ! It's easy to implement a mechanical mechanism to take the photograph. It could be based on a timer.

However, you do not know how your camera will land ! So installing 6 cameras viewing in each direction and triggered at the same time.

The main pb is : how to handle pressure ? How much pressure ? about 80 bars [X(] [X(] [X(] ....

I fear the bottom part of the lake is VERY dirty [:'(] ...
Old 03-03-2004, 08:10 PM
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Default RE: DEEP WATER: Transmission?

From what I have learned with the 1.2ghz stuff I seriously doubt it would transmit thru a wet sponge let alone almost 40 fathoms of water.[sm=drowning.gif]
ORIGINAL: ///samson

I'll def. try a wired camera at some point -- but first I want to know if my 1.2ghz wireless cam will transmit through water (perhaps with a submerged antenna).

Anyone?
Old 03-09-2004, 01:30 PM
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Default RE: DEEP WATER: Transmission?

Radio waves as you're familiar with does travel on water but the attenuation is so hard that it is dead an inch away from the tx.
The only way to transmitt under water is by very long wave lengh, like ultrasound or very low radio frequencies. The problem is to modulate a high frequency information (Video=4Mhz) into a low frequency carrier (ultrasound=40Khz).
The tech to do it don't seems to be open for regular users like us, as far as I know.

Nilo
Old 03-10-2004, 12:51 PM
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phantom4099
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Default RE: DEEP WATER: Transmission?

I have one of those cheap ebay cameras, and I placed one in the sink (in a few plastic bags) and had the reciever near by. It did not seem to have much of a problem with a few inches of water, so it might work if you place the anntane close by. I may have to try this again with my clear pelician case in the bath tub (I won't be in there at the same time).

Wyatt W.
Old 03-11-2004, 12:34 PM
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Default RE: DEEP WATER: Transmission?

I checked the cameras i have and they are rated for 90' but I would guess they could go deeper??? [link=http://www.csi-speco.com/cart/products/downloads/default.asp?durl=%2Fcart%2Fproducts%2Fdownloads%2F hirezImage%2FCVC%2D325W%2EJPG]picture of cam[/link]

I think using a wired cam would no be a bad idea, because you could also use the wire for control and retrieval ...

Do you have UUV?
Old 03-12-2004, 01:34 PM
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billmi
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Default RE: DEEP WATER: Transmission?

Radio waves propagate very poorly through water.

That's why ROVs and underwater communication equipment are set up to communicate through cables our acoustic signals.

If you're going to seal the camera, eliminating all voids with silicone, you might want to just pick up a cheap camera for the job - a black and white (if you're illuminating with IR this is your best bet) microcamera can be had for about $30, for a bit more you can get one with an array of IR LEDs on the same board. mpja.com carries lots of surplus microcameras and the like - this camera would do the trick well:

http://www.mpja.com/productview.asp?product=11691+ST

If you can build a good housing you can save a bit of money over commercial products like this:
http://www.jwfishers.com/dv1.htm

Even land based, you're better with a cable than RF if you want to get the cleanest signal you can. Even worrying about signal propagation through coper - the resistance on a couple hundred foot run, is competing with the waveform resolution lost when encoding over a carrier signal, and further when you take into account interference.

-Bill
Old 03-23-2004, 10:28 AM
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Timberviking
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Default RE: DEEP WATER: Transmission?

80 Bar????? The pressure at 200 ft is no where near 80 Bar (1160 PSI)! The pressure at 200 feet is 8X that of atmosphere, or 8 Bar (116 PSI). Pressure at depth increases by 1 ATM for every 33 feet. Makes a big difference. Samsons pressure vessel should work just fine. He will need a minimum of 3/8 thick polycarbonate for his lens, I'm using 1/2, but my viewing port is 4 1/2 inches.

-Matt
Old 03-23-2004, 11:11 AM
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///samson
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Default RE: DEEP WATER: Transmission?

MATT - good to see you make it over here to this board. How's the project coming along?

I have a new camera on the way from E-bay : http://cgi.ebay.com/ws/eBayISAPI.dll...category=48629 (add ebay . com where the *** are)

As far as I'm concerned, it should do the job just fine - and a little leakage would be OK since it is "water proof" already. The problem I have come across is sealing the lense tight enough,,,, gobs and gobs of sylicon glue won't do the trick. I'm HOPING this camera when it comes is small enough that I won't need a large surface area for the plexi. I'll toss up pictures soon. I hope to have something put together to test in Green Lake this weekend.

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