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From: chidsey@smoke.brl.mil (Irving Chidsey)
Newsgroups: sci.military
Subject: Re: Sub communications Correction
Message-ID: <1990Jun6.133015.2661@cbnews.att.com>
Date: 6 Jun 90 13:30:15 GMT
References: <15387@cbnews.ATT.COM> <15456@cbnews.ATT.COM> <15508@cbnews.ATT.COM> <16050@cbnews.ATT.COM>
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From: Irving Chidsey <chidsey@smoke.brl.mil>

In article <16050@cbnews.ATT.COM> moscom!de@cs.rochester.edu (Dave Esan) writes:
<
<From: moscom!de@cs.rochester.edu (Dave Esan)
<
<In article <15508@cbnews.ATT.COM> terryr@ogicse.ogi.edu (Terry Rooker) writes:
<>From: terryr@ogicse.ogi.edu (Terry Rooker)
<>In article <15456@cbnews.ATT.COM> terryr@ogicse.ogi.edu (Terry Rooker) writes:
<>>I don't know what the sub communication myth is.  Any elementary
<>>science text will tell you radio waves to penetrate water very well.
<> That should be radio waves do NOT penetrate water!
<
<Many years ago I read an account of a WWII submarine commander and his exploits
<in the Pacific.  It was interesting reading, although both the title and the 
<author's name escape me at the moment.  He served with Mush Morton, and Dick
<O'Kane, and was commander of the Wahoo (which sank the most tonnage of any US
<sub in the war) at the War's end.
<
<In any case, at one point in the war he was assigned to a sub under 
<construction at a port in one of the Great Lakes.  During its trials, he
<realized that there are several differences between salt and fresh water,
<one of which is that you can use the radio in fresh water, but not is sea
<water.  
<-- 
< -->     David Esan      {rutgers, ames, harvard}!rochester!moscom!de

	Electromagnetic waves do not penetrate very far into conductors,
but they do penetrate a little in the process of reflecting off the 'surface'.
The actual penetration is about 1/4 wavelength as measured in the conductor.
The intensity of the wave, falls off exponentialy, so a strong signal may
well be measurable at slightly greater depths.

	This is the main reason for the very low frequency: to make the
wavelength in the water long enough so that the sub can still make out the 
signal when it is out of sight.  Unfortunately, the signal bandwidth is severely
limited.

								Irv

-- 
I do not have signature authority.  I am not authorized to sign anything.
I am not authorized to commit the BRL, the DOA, the DOD, or the US Government
to anything, not even by implication.
			Irving L. Chidsey  <chidsey@brl.mil>