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v8power
Joined: 07 Feb 2002
Posts: 15
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 05 Oct 2003 4:42 Transmitting under water |
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I have been working with transmtter modules that have been working quite well I want to try using them for a under water project. is there any thing that I will need to look at or is it proetty much the same as air transmissions?
Last edited by v8power on 05 Oct 2003 5:18; edited 1 time in total |
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flatulent
Joined: 19 Jul 2002
Posts: 4856
Helped: 292
Location: Middle Earth
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| 05 Oct 2003 4:59 media impedance |
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| Is this radio or sonar? If radio, you will have trouble with the water because the dielectric constant is 81 which reduces the wavelength by 9 times. You will get severe attenuation for long distances or if you want to go from the water to air. Salt water is very conductive and you require kW to MW transmitters with low bit rates (under 1 bit/second).
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v8power
Joined: 07 Feb 2002
Posts: 15
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| 05 Oct 2003 5:17 Re: Transmitting under water |
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I am using the Linx 916 ES transmitters trandmitting at 38400 buad. air distance is about 1000' they are fully potted and sealed.
all I need is about 10' to 15' under water do you think this will happen with no modifications??? at a maximum depth of about 150'
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flatulent
Joined: 19 Jul 2002
Posts: 4856
Helped: 292
Location: Middle Earth
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| 05 Oct 2003 16:57 problems |
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| Try them in a bath tub, then a pond. It is hard to guess your results. You only need 1% of range so it may work.
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mr_ghz
Joined: 01 Apr 2002
Posts: 294
Helped: 2
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| 05 Oct 2003 18:02 Re: Transmitting under water |
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Hi v8power
What is the frequency of your transmitter? Some frequencies are much more attenuated than others. Use low frequencies for under water transmissions.
Bye
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ash
Joined: 25 Dec 2002
Posts: 160
Location: Europe
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| 05 Oct 2003 18:06 |
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| You need fiberoptic communication, otherwise the distance will be extremely reduced.
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D1_DRE
Joined: 26 Apr 2002
Posts: 61
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| 05 Oct 2003 18:22 Re: Transmitting under water |
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| Why working with radio transmitters when u can use ultrasonic modules which work pretty well in water? Unless of course your application specifically requires radio transmitter. Otherwise a combination of both technologies is also feasible
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v8power
Joined: 07 Feb 2002
Posts: 15
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| 06 Oct 2003 0:12 Re: Transmitting under water |
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| 916MHz. I am open to using any thing, the reason I ant to use the transmitters is cause I already use them for a product my comapny makes. so it would be easy. I dont care if the distance is reduces I only need at most 10 feet its for a scuba diving project.
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v8power
Joined: 07 Feb 2002
Posts: 15
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| 06 Oct 2003 0:13 Re: Transmitting under water |
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| D1_DRE wrote: |
| Why working with radio transmitters when u can use ultrasonic modules which work pretty well in water? Unless of course your application specifically requires radio transmitter. Otherwise a combination of both technologies is also feasible |
do you have any links to a --- drop in module??? for ultra sonic
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mr_ghz
Joined: 01 Apr 2002
Posts: 294
Helped: 2
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| 06 Oct 2003 19:33 Re: Transmitting under water |
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Hi v8power
I don't think that you'll have good link quality at 900MHz. If you need radio communication try frequencies in KW bands as 27MHz or lower. Using ultrasonic seems to me a good idea.
Bye
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ash
Joined: 25 Dec 2002
Posts: 160
Location: Europe
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| 06 Oct 2003 20:42 |
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High frequency ultrasonic communication in water has very very bad effects on habitat. Fiberoptics, yes they're expensive but how much is earth? For clear world what will you spend? Try low frequency ultrasonic or fiberoptic communication.
Regards.
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