RF through water question

[Ron H.]

What are the design issues involved with passing medium wave ( 10s of MHz )
higher power ( KWatts) RF through a water jacket. Assume "tap" water and of
course non conductive non ferrous housing material.

Ron H.

 

[Scott Stephens]

Ron H. wrote:

What are the design issues involved with passing medium wave ( 10s of MHz )
higher power ( KWatts) RF through a water jacket. Assume "tap" water and of
course non conductive non ferrous housing material.

Ron H.

Checkout: http://www.qsl.net/vk5br/UwaterComms.htm

--
Scott

**********************************

DIY Piezo-Gyro, PCB Drill Bot & More Soon!

http://home.comcast.net/~scottxs/

**********************************

 

On Tue, 11 May 2004 10:59:28 -0500, "Ron H." <ronharshbarger@mmm.com> wrote:

What are the design issues involved with passing medium wave ( 10s of MHz )
higher power ( KWatts) RF through a water jacket. Assume "tap" water and of
course non conductive non ferrous housing material.

Ron H.

Um.. unless your water is de-ionized or distilled, you don't pass RF through it.
It gets absorbed and turned into heat just like in a microwave oven. Tap water
is not de-ionized.

 

[John Popelish]

"Ron H." wrote:

What are the design issues involved with passing medium wave ( 10s of MHz )
higher power ( KWatts) RF through a water jacket. Assume "tap" water and of
course non conductive non ferrous housing material.

Ron H.

At a frequency somewhere around 1 gigahertz, water (even pure water)
changes from a dielectric to a lossy dielectric. At frequencies well
below 1 gigahertz, water should perform much like any other high
dielectric constant material, with loss depending mainly on the
conductivity and thus the ionic contaminants.

See:
http://www.lsbu.ac.uk/water/microwave.html
--
John Popelish

 

[Tim Auton]

crusty@usa.net wrote:

On Tue, 11 May 2004 10:59:28 -0500, "Ron H." <ronharshbarger@mmm.com> wrote:

What are the design issues involved with passing medium wave ( 10s of MHz )
higher power ( KWatts) RF through a water jacket. Assume "tap" water and of
course non conductive non ferrous housing material.

Um.. unless your water is de-ionized or distilled, you don't pass RF through it.

How do you think they talk to submarines? (the answer is: slowly!) You
can pass RF through water (even sea water), but unless it's very low
frequency (or extremely low - ELF) it doesn't get very far. You'd get
serious attenuation with 10s of MHz.


Tim
--
Love is a travelator.

 

[Winfield Hill]

Tim Auton wrote...

How do you think they talk to submarines? (the answer is: slowly!) You
can pass RF through water (even sea water), but unless it's very low
frequency (or extremely low - ELF) it doesn't get very far. You'd get
serious attenuation with 10s of MHz.

For the most part, with acoustic signaling. And sub-20kHz ELF,
but only if the sub is near the surface and trailing an antenna.

Thanks,
- Win

(email: use hill_at_rowland-dot-org for now)

 

[Repeating Rifle]

in article c7qt90$mej$1@tuvok3.mmm.com, Ron H. at ronharshbarger@mmm.com
wrote on 5/11/04 8:59 AM:

What are the design issues involved with passing medium wave ( 10s of MHz )
higher power ( KWatts) RF through a water jacket. Assume "tap" water and of
course non conductive non ferrous housing material.

Ron H.



Read and understand one of my favorite texts or one of its successors: Ramo

and Whinnery, "Fields and Waves in Modern Radio." Learn how to calculate
skin depth. Look up appropriate values for conductivity and dielectric
constant. End up by doing the calculations. They are easy using a modern
scientific calculator.

Otherwise, send me a check for $200, and we can negotiate what you get for
that.

Bill

 

[maxfoo]

On Tue, 11 May 2004 23:03:45 +0100, Tim Auton
<tim.auton@uton.[groupSexWithoutTheY]> wrote:

crusty@usa.net wrote:
On Tue, 11 May 2004 10:59:28 -0500, "Ron H." <ronharshbarger@mmm.com> wrote:

What are the design issues involved with passing medium wave ( 10s of MHz )
higher power ( KWatts) RF through a water jacket. Assume "tap" water and of
course non conductive non ferrous housing material.

Um.. unless your water is de-ionized or distilled, you don't pass RF through it.

How do you think they talk to submarines? (the answer is: slowly!) You
can pass RF through water (even sea water), but unless it's very low
frequency (or extremely low - ELF) it doesn't get very far. You'd get
serious attenuation with 10s of MHz.


Tim

like this...

http://www.darpa.mil/ato/programs/bcaa.htm




Remove "HeadFromButt", before replying by email.

 

[Tim Auton]

Winfield Hill <Winfield_member@newsguy.com> wrote:

Tim Auton wrote...

How do you think they talk to submarines? (the answer is: slowly!) You
can pass RF through water (even sea water), but unless it's very low
frequency (or extremely low - ELF) it doesn't get very far. You'd get
serious attenuation with 10s of MHz.

For the most part, with acoustic signaling. And sub-20kHz ELF,
but only if the sub is near the surface and trailing an antenna.

AFAIK VLF (3-20kHz) is only used near the surface with a trailing
antenna, but the latest ELF systems have neither requirement. What I
can find on the ELF system in use by the US (76Hz) suggests they can
receive ELF at operational speed and depth, which doesn't suggest
"near the surface" to me. It's all relative of course and hard figures
are hard to come by (hardly surprising!), but I've seen 2-300m
mentioned. AIUI they use on/in-hull antennas (presumably SQUID based)
instead of trailing wire antennas for ELF too.

OK, perhaps it's not how they /usually/ talk to submarines though


Tim
--
Love is a travelator.

 

[Winfield Hill]

Tim Auton <tim.auton@uton.[groupSexWithoutTheY]> wrote...

What I can find on the ELF system in use by the US (76Hz)
suggests they can receive ELF at operational speed and depth...

Wow, 76Hz? And this stuff is being discussed in public?

Thanks,
- Win

(email: use hill_at_rowland-dot-org for now)

 

[Tim Auton]

Winfield Hill <Winfield_member@newsguy.com> wrote:

> wrote...

What I can find on the ELF system in use by the US (76Hz)
suggests they can receive ELF at operational speed and depth...

Wow, 76Hz? And this stuff is being discussed in public?

76Hz indeed. Wavelengths of thousands of km. Antenna *feedlines* tens
of km long. It's fascinating stuff. If it's meant to be a secret
they're not doing a very good job of keeping it

Do a search, there's info out there on the 'net ('ELF submarine'
should get you started). Here's some info on the Russian equivalent
system (Zevs) that gives a pretty good overview.

http://web.tiscali.it/vlfradio/zevs/zevs.htm


Tim
--
Love is a travelator.

 

[The other John Smith]

"Winfield Hill" <Winfield_member@newsguy.com> wrote in message
news:c7rsjb027tj@drn.newsguy.com...

> wrote...

What I can find on the ELF system in use by the US (76Hz)
suggests they can receive ELF at operational speed and depth...

Wow, 76Hz? And this stuff is being discussed in public?

Thanks,
- Win

(email: use hill_at_rowland-dot-org for now)

Yes. About 10 or so years ago, when I worked for a company who made variable
speed motor controllers, an engineer with Continental Electronics called and
asked about our 250 kW inverters. During the question/answer process, it
came out that he wanted an output of about 250 kW with frequency variation
of something less than 60 Hz to near 100 Hz to communicate with submarines.
Huh? I said, you can't pass any information with a carrier at that
frequency. He said it all depends on how it's modulated and how much time
you take to decode it. That shut me up.

I'll never forget that phone call.

John

 

[bushbadee]

Messages can be transmitted by morse code at those frequencies.
But we have better methods now of communicating with Subs under the water.
It is called Blue light which penitrates sea water to pretty good depths.
They do not talk about it much but if you can talk to a sub with blue light,
then you should be able to detect bounce back and locate subs under the
ocean.
I forget for the momment the names of those lasers.

I once worked on a laser of that type and the voltage was so high that it
made it's way around about 4 feet of Plexiglass insulator to spark. Left a
carbon streak on the Plexiglass and it had to be replaced.



"The other John Smith" <jocjo-john@yooha.com> wrote in message
news:fRhoc.17005$V97.15931@newsread1.news.pas.earthlink.net...

"Winfield Hill" <Winfield_member@newsguy.com> wrote in message
news:c7rsjb027tj@drn.newsguy.com...
Tim Auton <tim.auton@uton.[groupSexWithoutTheY]> wrote...

What I can find on the ELF system in use by the US (76Hz)
suggests they can receive ELF at operational speed and depth...

Wow, 76Hz? And this stuff is being discussed in public?

Thanks,
- Win

(email: use hill_at_rowland-dot-org for now)



Yes. About 10 or so years ago, when I worked for a company who made
variable
speed motor controllers, an engineer with Continental Electronics called
and
asked about our 250 kW inverters. During the question/answer process, it
came out that he wanted an output of about 250 kW with frequency variation
of something less than 60 Hz to near 100 Hz to communicate with
submarines.
Huh? I said, you can't pass any information with a carrier at that
frequency. He said it all depends on how it's modulated and how much time
you take to decode it. That shut me up.

I'll never forget that phone call.

John

 

[Max Hauser]

"Repeating Rifle" in news:BCC6A5B1.173B6%SalmonEgg@sbcglobal.net...:

Read and understand one of my favorite texts or one of its
successors: Ramo and Whinnery, "Fields and Waves in Modern Radio."
Learn how to calculate skin depth. Look up appropriate values for
conductivity and dielectric constant. End up by doing the calculations.
They are easy using a modern scientific calculator.

Or if you are really, really desperate, search Usenet archives for the
phrase "skin depth" in the year 1987.

There you may read (with growing awe, if you know the subject) one Commander
Brett Maraldo describing speaker cables of mercury-filled tubing, and an
ensuing Grand Debate -- as popular then as now -- on skin depth in
conductors: one camp insisting that depth of penetration is the electrical
wavelength at frequency, and the other group countering that it's the (!)
acoustical wavelength instead.

(At that time, and also in a follow-up, I too cited Ramo and Whinnery. For
what good it did, but maybe it did, who can say?)

Max

 

[Max Hauser]

"The other John Smith" in message
news:fRhoc.17005$V97.15931@newsread1.news.pas.earthlink.net...

During the question/answer process, it came out that he wanted
an output of about 250 kW with frequency variation of
something less than 60 Hz to near 100 Hz to communicate with
submarines. Huh? I said, you can't pass any information with a
carrier at that frequency. He said it all depends on how it's
modulated and how much time you take to decode it.

You're damn right it does. (The intuitive notion of a tight relationship
between bit rate and analog bandwidth disappears like parted waters if you
study communication theory -- you can have data rates far greater or far
less than bandwidths, in exchange for requirements for SNR or other
constraints.) But the subject tends to the counterintuitive, so it
collects notions and suppositions and opinions. (Like various other areas
of electronics.) This by the way is partly the domain of the newsgroup
comp.dsp .

 

[Repeating Rifle]

in article c7rsjb027tj@drn.newsguy.com, Winfield Hill at
Winfield_member@newsguy.com wrote on 5/11/04 5:54 PM:

> wrote...

What I can find on the ELF system in use by the US (76Hz)
suggests they can receive ELF at operational speed and depth...

Wow, 76Hz? And this stuff is being discussed in public?

Thanks,
- Win

(email: use hill_at_rowland-dot-org for now)

There is not much secret to it. The physics is well known and not
complicated. The trick will be to implement a working system. That is not
easy. There will be no way to prevent interception. I am sure that any
potential adversary is listening now. The key will be encryption and hiding
that there may have been successful communication.

Bill

 

[Repeating Rifle]

in article 10a3gi85h0aum79@corp.supernews.com, Max Hauser at
maxREMOVE@THIStdl.com wrote on 5/11/04 11:20 PM:

There you may read (with growing awe, if you know the subject) one Commander
Brett Maraldo describing speaker cables of mercury-filled tubing, and an
ensuing Grand Debate -- as popular then as now -- on skin depth in
conductors: one camp insisting that depth of penetration is the electrical
wavelength at frequency, and the other group countering that it's the (!)
acoustical wavelength instead.

I sometimes wonder about the sanity of some audiophiles. Although many do
indeed know what they are talking about, others are like Art Bell. What else
would explain the love affair with tube ampifiers, monster litz cables,
vinyl records over compact disks, and my favorite, a green marker to green
up the area around a CD spindle hole? To tell the truth, I have not heard
much about that last on letely. Is it still in vogue?

Bill

 

[Winfield Hill]

Tim Auton <tim.auton@uton.[groupSexWithoutTheY]> wrote...

Do a search, there's info out there on the 'net ('ELF submarine'
should get you started). Here's some info on the Russian equivalent
system (Zevs) that gives a pretty good overview.

http://web.tiscali.it/vlfradio/zevs/zevs.htm

Fascinating. Here're a few quotes from that site:

Why use ELF? "In the middle of the Atlantic ocean, with a salinity
of 3.2%, a VLF signal will penetrate down to a depth of 10-20
meter, barely periscope-depth for a modern large scale submarine."

"At the Zevs' military operating frequency (82Hz), the wavelength
more than 1/4 of the earth's diameter."

"frequency shift observed, in the narrow range 81Hz to 83.3Hz...
The carrier shift of only 2.3Hz makes up the difference in a mark
and a space of the MSK signal. ... The ELF carrier frequency is
shifted from the normal carrier frequency of 82Hz, down to 81.6Hz
and up to 82.7Hz, prior to this message. This is most likely the
'message waiting' call function of the Russian ZEVS transmitter."

"The coded message sent is a repeated, error correcting code. The
bit rate is a few bits per minute, repeated until enough data..."

Thanks,
- Win

(email: use hill_at_rowland-dot-org for now)

 

[Keith Wootten]

In message <c7t1i902kvo@drn.newsguy.com>, Winfield Hill
<Winfield_member@newsguy.com> writes

[snipped]

"The coded message sent is a repeated, error correcting code. The
bit rate is a few bits per minute, repeated until enough data..."

I bet they're mightily pissed off by HTML messages.

Cheers
--
Keith Wootten

 

[Winfield Hill]

Keith Wootten wrote...

Winfield Hill writes

"The coded message sent is a repeated, error correcting code. The
bit rate is a few bits per minute, repeated until enough data..."

I bet they're mightily pissed off by HTML messages.

Yes, and no binary attachements allowed.

Thanks,
- Win

(email: use hill_at_rowland-dot-org for now)