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Underwater tv



 
 
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  #1  
Old January 4th 17, 02:07 PM posted to uk.tech.digital-tv
Brian Gaff
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Posts: 6,570
Default Underwater tv

I was just thinking. If you wanted to transmit tv to an underwater habitat,
how could you do it? Presumably light can only go so far under water and
radio even less far.
Also I wonder what the speed of light is under water. as I suppose if you
measure it there its the same but it obviously refracts light so has, one
assumes to be different to free air.

Brian

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  #2  
Old January 4th 17, 04:49 PM posted to uk.tech.digital-tv
R. Mark Clayton[_2_]
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Posts: 436
Default Underwater tv

On Wednesday, 4 January 2017 15:07:13 UTC, Brian Gaff wrote:
I was just thinking. If you wanted to transmit tv to an underwater habitat,
how could you do it?


Wire or fibre, possible light.

Presumably light can only go so far under water and
radio even less far.
Also I wonder what the speed of light is under water.


About two thirds that in a vacuum / free air. Ditto copper.

Slower in diamond.

as I suppose if you
measure it there its the same but it obviously refracts light so has, one
assumes to be different to free air.

Brian

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  #4  
Old January 4th 17, 07:41 PM posted to uk.tech.digital-tv
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Posts: 174
Default Underwater tv

On Wednesday, 4 January 2017 15:07:13 UTC, Brian Gaff wrote:
I was just thinking. If you wanted to transmit tv to an underwater habitat,
how could you do it?


Trained dolphins carrying USB sticks?

Presumably by submarines you mean nuclear-powered ones, as any others would have to get close enough to the surface occasionally to recharge their batteries from engines and could do a download of a day's content.

Permanent underwater habitats would probably have electricity distribution, so could have cable TV and send an antenna buoy up to the surface periodically.

Owain

  #5  
Old January 4th 17, 09:10 PM posted to uk.tech.digital-tv
Benderthe.evilrobot
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Posts: 148
Default Underwater tv


They tend to go bang if they get wet.

Although a 12V portable I was working on once; proceeded to inductively heat
a puddle of water around the base of the horizontal output transformer.

The water actually started to boil.

  #6  
Old January 4th 17, 10:04 PM posted to uk.tech.digital-tv
Bill Wright[_3_]
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Posts: 1,676
Default Underwater tv

On 04/01/2017 17:49, R. Mark Clayton wrote:

Also I wonder what the speed of light is under water.


About two thirds that in a vacuum / free air. Ditto copper.


Since EM waves/particles travel in a vacuum it appears that don't need a
medium. Why then would they be slower in a medium, and stopped by some
media?

Bill

  #7  
Old January 5th 17, 06:42 AM posted to uk.tech.digital-tv
Brian Gaff
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Posts: 6,570
Default Underwater tv

Well using your logic, then any mountain that got in the way of a tv signal
should not matter.

I seem to recall that there are now human made materials with a negative
refractive index which seems counter intuitive.

And further on in this thread all those who want to operate tv under water
might wish to know that you can, apparently take the I phone7 down to 1
metre while its working without any problems as there are no longer any
holes in tha case for plugs to fit.
Does anyone recall that miracle stuff on Tomorros world where they showed
you could run a normal electric drill under water if you sprayed it in?
I never expected that to be saleable as you would probably have hod to keep
on doing it over and over to remain even semi safe. Of course the scceptics
amongst us suspected the water was distilled and non conductive in any
case.
Brian

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"Bill Wright" wrote in message
news
On 04/01/2017 17:49, R. Mark Clayton wrote:

Also I wonder what the speed of light is under water.


About two thirds that in a vacuum / free air. Ditto copper.


Since EM waves/particles travel in a vacuum it appears that don't need a
medium. Why then would they be slower in a medium, and stopped by some
media?

Bill



  #8  
Old January 5th 17, 06:44 AM posted to uk.tech.digital-tv
Brian Gaff
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Posts: 6,570
Default Underwater tv

Not recommended. tjhe little chinaman in the manual with the frown an
umbrella and a tv should point you this way I feel.

Brian

--
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This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
"Benderthe.evilrobot" wrote in message
...

They tend to go bang if they get wet.

Although a 12V portable I was working on once; proceeded to inductively
heat a puddle of water around the base of the horizontal output
transformer.

The water actually started to boil.



  #9  
Old January 5th 17, 08:17 AM posted to uk.tech.digital-tv
Norman Wells[_6_]
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Posts: 852
Default Underwater tv

"Bob Latham" wrote in message
...
In article ,
R. Mark Clayton wrote:
On Wednesday, 4 January 2017 15:07:13 UTC, Brian Gaff wrote:
I was just thinking. If you wanted to transmit tv to an underwater habitat,
how could you do it?


Wire or fibre, possible light.


Presumably light can only go so far under water and
radio even less far.
Also I wonder what the speed of light is under water.


About two thirds that in a vacuum / free air. Ditto copper.


Slower in diamond.


I don't understand. I thought Einstein had taught us that the speed of
light was a constant, always the same for all observers everywhere?


Then it wouldn't get bent by a prism.

It's constant 'in a vacuum' which is how it's properly expressed.

  #10  
Old January 5th 17, 10:58 AM posted to uk.tech.digital-tv
Davey
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Posts: 2,178
Default Underwater tv

On Thu, 5 Jan 2017 07:42:39 -0000
"Brian Gaff" wrote:

Well using your logic, then any mountain that got in the way of a tv
signal should not matter.

I seem to recall that there are now human made materials with a
negative refractive index which seems counter intuitive.

And further on in this thread all those who want to operate tv under
water might wish to know that you can, apparently take the I phone7
down to 1 metre while its working without any problems as there are
no longer any holes in tha case for plugs to fit.
Does anyone recall that miracle stuff on Tomorros world where they
showed you could run a normal electric drill under water if you
sprayed it in? I never expected that to be saleable as you would
probably have hod to keep on doing it over and over to remain even
semi safe. Of course the scceptics amongst us suspected the water
was distilled and non conductive in any case.
Brian


Once while I was working, we had a pump pit flood with water. The
pumps that were running kept running and were fine, the ones that
weren't running had to be dried out and some had to be rewound.

--
Davey.
 




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