Underwater
 

Quite possible, however, 13 Kc and 18 Kc fall into the VLF range. The
original poster mentioned ELF. ELF is down in the "cycles", we didn't
have "kilos" at our ELF transmitters ;)

Scott
N0EDV

Fred W4JLE wrote:
As I remember, we used 18 Kc and 13 Kc. We didn't have hertz in those days
:)

We were able to copy Jim Creek when submerged in the Red Sea. Jim Creek had
13 miles of wire suspended between two mountains in what was probably the
worlds biggest capacitance hat.

All CW , because even a 150 cycle shift for rtty would have thrown the tank
circuit out of resonance. Now no one would be able to copy it...


"Roy Lewallen" wrote in message
...

Asimov wrote:

Thanks for the info. I had read that submarines communicated in a
band of a few 10's of Hz because of the problems with water. As for
the polar molecules aligning themselves, this implies it takes some
time to achieve. Thus there is a resonnant point in this and if there
is resonnance then there might be anti-resonnance too. Might you know
where this natural molecular resonnance is? Might this be the standard
microwave oven frequency?

Sorry, I don't know. If any of the readers of this newsgroup do, I'd
really appreciate your enlightening us.

Roy Lewallen, W7EL

Underwater
 

One could couple into a crystal oscillator NAA's signal and then listen 15
kHz to the side of the oscillator's frequency for great CW practice. BIG
signal. 73 Mac N8TT

--
J. Mc Laughlin; Michigan U.S.A.
Home:
"Fred W4JLE" wrote in message
...
As I remember, we used 18 Kc and 13 Kc. We didn't have hertz in those days
:)

We were able to copy Jim Creek when submerged in the Red Sea. Jim Creek
had
13 miles of wire suspended between two mountains in what was probably the
worlds biggest capacitance hat.

All CW , because even a 150 cycle shift for rtty would have thrown the
tank
circuit out of resonance. Now no one would be able to copy it...

Underwater
 

Scott wrote:
Slight correction...our (U.S.) subs using ELF worked at about 50-80 Hz.
I worked at one of the land-based transmitters for 5 years.

Scott


Tim Wescott wrote:

Asimov wrote:

Hi,

I was thinking about why radio wave communications are not generally
used underwater. Basically I'm asking what are the quantitative
components of the underwater medium that makes it impractical except
for perhaps very short ranges. Things like attenuation, impedance,
etc... Does any one here know these details or have them handy?

A*s*i*m*o*v

... Acme Corp: Unlimited credit for disadvantaged coyotes.

The conductivity of water causes great attenuation at all but very low
frequencies. Think "skin effect".

That having been said, the US Navy (and probably all other folks with
subs) use extremely low frequency RF (30kHz IIRC) to communicate with
strategic nuclear subs.

Boy I'm glad for that "IIRC" I put in there. Thanks.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Underwater
 

No problem! The Navy kept fairly quiet about their ELF communications.
They shut down the ELF transmitters a little over a year ago. Wonder
what they're using as a replacement? They were doing experiments with a
satellite based green laser I had heard (while I was still working at
Project ELF)...The ELF signal used MSK modulation (Minimum Shift
Keying), which is similar to RTTY, only the shift between Mark and Space
was 4 or 8 Hz, depending on rate of transmission. Took 5 minutes to
send 3 alpha characters...most hams wouldn't have the patience to copy
at that speed ;)



Scott



Tim Wescott wrote:

Scott wrote:

Slight correction...our (U.S.) subs using ELF worked at about 50-80
Hz. I worked at one of the land-based transmitters for 5 years.

Scott


Tim Wescott wrote:

Asimov wrote:

Hi,

I was thinking about why radio wave communications are not generally
used underwater. Basically I'm asking what are the quantitative
components of the underwater medium that makes it impractical except
for perhaps very short ranges. Things like attenuation, impedance,
etc... Does any one here know these details or have them handy?

A*s*i*m*o*v

... Acme Corp: Unlimited credit for disadvantaged coyotes.

The conductivity of water causes great attenuation at all but very
low frequencies. Think "skin effect".

That having been said, the US Navy (and probably all other folks with
subs) use extremely low frequency RF (30kHz IIRC) to communicate with
strategic nuclear subs.

Boy I'm glad for that "IIRC" I put in there. Thanks.