RE: [PSUBS-MAILIST] Undersea communications & retractable buoy

[Alex <spm2@nomad.ignorelist.com>]

For listening only you could get away with a ferride rod antenna couldn't you.
I knew someone who built radios for communication to people inside caves. The
main problem was of course fitting an antenna in. Then the other thing was
that inside the cave the radio frequency was pretty quiet making it easy to
listen, but on the surface there was a lot of noise on the frequency so that
the guy in the cave needed a lot of transmitter power to reach the surface. I
think they used something in the 50 - 100Khz frequency range.

Alex

On 30-Oct-2009 Jay K. Jeffries wrote:
> Alex,
> A UQC uses ultrasound on a carrier and single side-band for efficiency.
> 
> 1.9 MHz has limited penetration into the water column and Extreme Low
> Frequency (ELF) due to its very low frequency (used by the Navy) can carry
> very little data (typically 3-letter codes) and has to have VERY long
> antennas driven by a lot of power to reach submarines (so the submarine has
> to deploy a VERY long antenna also).
> R/Jay
> KF4DBI
> 
> -----Original Message-----
> From: owner-personal_submersibles@psubs.org
> [mailto:owner-personal_submersibles@psubs.org] On Behalf Of Alex
> Sent: Thursday, October 29, 2009 11:33 PM
> To: personal_submersibles@psubs.org
> Subject: RE: [PSUBS-MAILIST] Undersea communications & retractable buoy
> 
> I was thinking: You know there are the hydrophones that work quite well for
> communicating. I was just reading about them working to 500ft depth, but I
> suppose with a lot of background noise and stuff it could be a problem.
> 
> What if, you were to use amplitude modulated ultrasound to communicate? You
> could have a 50khz carrier and that would eliminate the interference
> problem!
> 
> Also, how well do regular radios work for this purpose? How well would the
> 160m
> (1.9MHz) HAM band work for this? If you were to bring a pocket AM radio down
> in the sub with you and have it inside the transparent dome how far down
> could you go and have it still work? You know those "atomic clocks" set
> themselves by picking up the 60khz signal from Colorado I think it is, how
> far under could you use one of those?
> 
> The military uses something like 15khz to transmit globally to the their
> submerged submarines.
> 
> 
> 
> 
> 
> 
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-- 
Mailed with XFmail on 30-Oct-2009.
God saved Noah, but Noah had to build an ark!



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