Rf into seawater penetration?

[Rubicon]

Hello,

Does anyone have an accurate estimate of how deeply, if at all a
common childs remote controlled toy cars transmission can penetrate
seawater to control the car? A difficult question I admit!

Also:
Are there any RF frequencies that are better at penetrating seawater
than others and if so what are they?

The application is for a 15m max, close range transmitter of some sort
(RF, IR?) to remotely instruct an under water (up to 7meters deep -
tidal) device to activate a solenoid or motor. Most probably it's be a
motor or servo of some sort as solenoids are so expensive and using a
cheap toys components would be an advantage for costs sake.

Bearing in mind the current global situation you can rest assured it's
for nothing sinister but for a device my employer has in mind for
rescuing lost and preventing stolen boating equipment.

Funny that after over three years of constantly hearing every single
step and problem involved in its double hulled home built construction
that's about all I can remenber of his boat apart from the fact it's a
Hartely design. I think? Oh it was suggestred by another that I use an
auger and bit to drill through from the inside below the waterline to
the fiberglass outer layer so that when it got into heavy seas it'd
burst and sink. Ahhh... I can almost see it now...

Cheers,

Andrew.
Remove the ZZ from E-Mail address to contact me.

 

[John Fields]

On Tue, 10 Feb 2004 08:25:09 GMT, zzrubicon@netaccess.co.nz (Rubicon)
wrote:

Hello,

Does anyone have an accurate estimate of how deeply, if at all a
common childs remote controlled toy cars transmission can penetrate
seawater to control the car? A difficult question I admit!

Also:
Are there any RF frequencies that are better at penetrating seawater
than others and if so what are they?

The application is for a 15m max, close range transmitter of some sort
(RF, IR?) to remotely instruct an under water (up to 7meters deep -
tidal) device to activate a solenoid or motor. Most probably it's be a
motor or servo of some sort as solenoids are so expensive and using a
cheap toys components would be an advantage for costs sake.

---
Forget RF and IR, use acoustics.

--
John Fields

 

[Dr. Anton T. Squeegee]

In article <40288b17.5158128@news.netaccess.co.nz>,
zzrubicon@netaccess.co.nz says...

Hello,

Does anyone have an accurate estimate of how deeply, if at all a
common childs remote controlled toy cars transmission can penetrate
seawater to control the car? A difficult question I admit!

<snippety>

Let me put it this way. Ther are good reasons why the Navy uses
VLF transmitters to communicate with their subs. ;-)

Honestly, I'd be surprised if a toy-car transmitter was usable to
more than a foot or so of depth.

Remember what you're dealing with. Seawater is a pretty good
electrical conductor, and the ocean is the world's biggest ground plane.


--
Dr. Anton Squeegee, Director, Dutch Surrealist Plumbing Institute
(Known to some as Bruce Lane, KC7GR)
kyrrin a/t bluefeathertech d-o=t c&o&m
Motorola Radio Programming & Service Available -
http://www.bluefeathertech.com/rf.html
"Quando Omni Flunkus Moritati" (Red Green)

 

[George]

zzrubicon@netaccess.co.nz (Rubicon) wrote in message news:<40288b17.5158128@news.netaccess.co.nz>...

Hello,

Does anyone have an accurate estimate of how deeply, if at all a
common childs remote controlled toy cars transmission can penetrate
seawater to control the car? A difficult question I admit!

Also:
Are there any RF frequencies that are better at penetrating seawater
than others and if so what are they?

The application is for a 15m max, close range transmitter of some sort
(RF, IR?) to remotely instruct an under water (up to 7meters deep -
tidal) device to activate a solenoid or motor. Most probably it's be a
motor or servo of some sort as solenoids are so expensive and using a
cheap toys components would be an advantage for costs sake.

Bearing in mind the current global situation you can rest assured it's
for nothing sinister but for a device my employer has in mind for
rescuing lost and preventing stolen boating equipment.

Funny that after over three years of constantly hearing every single
step and problem involved in its double hulled home built construction
that's about all I can remenber of his boat apart from the fact it's a
Hartely design. I think? Oh it was suggestred by another that I use an
auger and bit to drill through from the inside below the waterline to
the fiberglass outer layer so that when it got into heavy seas it'd
burst and sink. Ahhh... I can almost see it now...

Cheers,

Andrew.
Remove the ZZ from E-Mail address to contact me.

RF or IR won't work through several meters of water. Water is used to
absorb them in labs. I don't know much about antennas but you should
probably consider having an antenna on a float with the signal sent
down a wire to the device below. The only EM radiation I can think
that might penetrate coherently that deep is like blue-green laser.

 

[George]

zzrubicon@netaccess.co.nz (Rubicon) wrote in message news:<40288b17.5158128@news.netaccess.co.nz>...

Hello,

Does anyone have an accurate estimate of how deeply, if at all a
common childs remote controlled toy cars transmission can penetrate
seawater to control the car? A difficult question I admit!

Also:
Are there any RF frequencies that are better at penetrating seawater
than others and if so what are they?

The application is for a 15m max, close range transmitter of some sort
(RF, IR?) to remotely instruct an under water (up to 7meters deep -
tidal) device to activate a solenoid or motor. Most probably it's be a
motor or servo of some sort as solenoids are so expensive and using a
cheap toys components would be an advantage for costs sake.

Bearing in mind the current global situation you can rest assured it's
for nothing sinister but for a device my employer has in mind for
rescuing lost and preventing stolen boating equipment.

Funny that after over three years of constantly hearing every single
step and problem involved in its double hulled home built construction
that's about all I can remenber of his boat apart from the fact it's a
Hartely design. I think? Oh it was suggestred by another that I use an
auger and bit to drill through from the inside below the waterline to
the fiberglass outer layer so that when it got into heavy seas it'd
burst and sink. Ahhh... I can almost see it now...

Cheers,

Andrew.
Remove the ZZ from E-Mail address to contact me.

Oh yeah, and the fact that it's seawater increases the absorption
rate. The absorption rate is proportional to conductivity which is
proportional to the amount of ions in the water.

 

[Dr Engelbert Buxbaum]

Rubicon wrote:

Does anyone have an accurate estimate of how deeply, if at all a
common childs remote controlled toy cars transmission can penetrate
seawater to control the car? A difficult question I admit!

Very low frequency (approx 10 kHz) waves are routinely used for contact
to submarines, but the antennas are rather big.

I do however remember reading a paper on a communication device used for
cave rescue, called the mole-phone. Apparently it relies on the magnetic
rather than the electrical component of the field and hence works
several hundred meters through rocks. Conceivably this should also work
under water.

 

[Eric R Snow]

On Tue, 10 Feb 2004 09:27:01 +0100, Dr Engelbert Buxbaum
<engelbert_buxbaum@hotmail.com> wrote:

Rubicon wrote:

Does anyone have an accurate estimate of how deeply, if at all a
common childs remote controlled toy cars transmission can penetrate
seawater to control the car? A difficult question I admit!

Very low frequency (approx 10 kHz) waves are routinely used for contact
to submarines, but the antennas are rather big.

I do however remember reading a paper on a communication device used for
cave rescue, called the mole-phone. Apparently it relies on the magnetic
rather than the electrical component of the field and hence works
several hundred meters through rocks. Conceivably this should also work
under water.
I was just reading, a month or so ago, in Nuts & Volts about a system

that uses inductance as the transmitting medium. The article described
a setup where the transmitting antenna was a wire loop surrounding a
room. Then a coil was used to pick up, through inductance, the signal.
The pickup used in the article was one from Radio Shack that is
normally used as a phone pickup. The kind that uses suction to stick
to the phone, The article mentioned this type of system for
communication with cavers. Maybe that's what a "mole phone" is. But I
know hardly anything about electronics and have no idea if this would
work very well through salt or fresh water. I do remember reading that
the sound quality was good enough for voice but lacking for music. As
a scuba diver I can attest to how well sound travels through water. It
seems that an ultrasonic transducer mounted to the inside wall of a
stainless steel enclosure would work well. I'm sure false triggering
could be avoided the same way IR remotes work. The signal is modulated
at a certain frequency so the reciever pays attention to that. Maybe
the transducer could just be pulsed on and off at a certain frequency
to achieve the same thing.
ERS

 

[Rubicon]

Hello.

Yes... I thought as much after so many sub movies over the years
however as they go much deeper than the approx 7m depth intended I
wasn't completely sure about the penetration of "regular" RF into
seawater.
A search before posting here resulted in Navy related documents and
hi-tech articles Thanks for eliminating that avenue.

The small bouy with an antenna would be easier for a "rank" amateur
like me to rig up but it's not what he wants.

Ultrasound is what I originallly thought of and it looks like the way
to go. The schematics I've seen so far on the net are ultrasound
switches and prone to naturally produced activation. Does anyone know
where to find a modulated ultrasound switch schematic?

In addition I'm wondering if the transmitter and receiver work well in
water resistant enclosures? Are there any special housing requirements
here?

Thanks for all your help.

Andrew.




I had also for some reason thought of a pulsed strobe triggering a
sensor but that seems a little





On Mon, 9 Feb 2004 07:22:08 -0800, Dr. Anton T. Squeegee
<SpammersArePondScum@dev.null> wrote:

In article <40288b17.5158128@news.netaccess.co.nz>,
zzrubicon@netaccess.co.nz says...

Hello,

Does anyone have an accurate estimate of how deeply, if at all a
common childs remote controlled toy cars transmission can penetrate
seawater to control the car? A difficult question I admit!

snippety

Let me put it this way. Ther are good reasons why the Navy uses
VLF transmitters to communicate with their subs. ;-)

Honestly, I'd be surprised if a toy-car transmitter was usable to
more than a foot or so of depth.

Remember what you're dealing with. Seawater is a pretty good
electrical conductor, and the ocean is the world's biggest ground plane.


--
Dr. Anton Squeegee, Director, Dutch Surrealist Plumbing Institute
(Known to some as Bruce Lane, KC7GR)
kyrrin a/t bluefeathertech d-o=t c&o&m
Motorola Radio Programming & Service Available -
http://www.bluefeathertech.com/rf.html
"Quando Omni Flunkus Moritati" (Red Green)

Remove the ZZ from E-Mail address to contact me.

 

[Rubicon]

Sorry, missed this part.

I had also for some reason thought of a pulsed strobe triggering a
.sensor but that seems a little

Awkward?!

Andrew.



On Wed, 11 Feb 2004 05:13:30 GMT, zzrubicon@netaccess.co.nz (Rubicon)
wrote:

Hello.

Yes... I thought as much after so many sub movies over the years
however as they go much deeper than the approx 7m depth intended I
wasn't completely sure about the penetration of "regular" RF into
seawater.
A search before posting here resulted in Navy related documents and
hi-tech articles Thanks for eliminating that avenue.

The small bouy with an antenna would be easier for a "rank" amateur
like me to rig up but it's not what he wants.

Ultrasound is what I originallly thought of and it looks like the way
to go. The schematics I've seen so far on the net are ultrasound
switches and prone to naturally produced activation. Does anyone know
where to find a modulated ultrasound switch schematic?

In addition I'm wondering if the transmitter and receiver work well in
water resistant enclosures? Are there any special housing requirements
here?

Thanks for all your help.

Andrew.




I had also for some reason thought of a pulsed strobe triggering a
sensor but that seems a little





On Mon, 9 Feb 2004 07:22:08 -0800, Dr. Anton T. Squeegee
SpammersArePondScum@dev.null> wrote:

In article <40288b17.5158128@news.netaccess.co.nz>,
zzrubicon@netaccess.co.nz says...

Hello,

Does anyone have an accurate estimate of how deeply, if at all a
common childs remote controlled toy cars transmission can penetrate
seawater to control the car? A difficult question I admit!

snippety

Let me put it this way. Ther are good reasons why the Navy uses
VLF transmitters to communicate with their subs. ;-)

Honestly, I'd be surprised if a toy-car transmitter was usable to
more than a foot or so of depth.

Remember what you're dealing with. Seawater is a pretty good
electrical conductor, and the ocean is the world's biggest ground plane.


--
Dr. Anton Squeegee, Director, Dutch Surrealist Plumbing Institute
(Known to some as Bruce Lane, KC7GR)
kyrrin a/t bluefeathertech d-o=t c&o&m
Motorola Radio Programming & Service Available -
http://www.bluefeathertech.com/rf.html
"Quando Omni Flunkus Moritati" (Red Green)

Remove the ZZ from E-Mail address to contact me.

Remove the ZZ from E-Mail address to contact me.

 

[Rubicon]

Thankyou all for your help.

Andrew.



On Tue, 10 Feb 2004 07:08:20 -0800, Eric R Snow <etpm@whidbey.com>
wrote:

On Tue, 10 Feb 2004 09:27:01 +0100, Dr Engelbert Buxbaum
engelbert_buxbaum@hotmail.com> wrote:

Rubicon wrote:

Does anyone have an accurate estimate of how deeply, if at all a
common childs remote controlled toy cars transmission can penetrate
seawater to control the car? A difficult question I admit!

Very low frequency (approx 10 kHz) waves are routinely used for contact
to submarines, but the antennas are rather big.

I do however remember reading a paper on a communication device used for
cave rescue, called the mole-phone. Apparently it relies on the magnetic
rather than the electrical component of the field and hence works
several hundred meters through rocks. Conceivably this should also work
under water.
I was just reading, a month or so ago, in Nuts & Volts about a system
that uses inductance as the transmitting medium. The article described
a setup where the transmitting antenna was a wire loop surrounding a
room. Then a coil was used to pick up, through inductance, the signal.
The pickup used in the article was one from Radio Shack that is
normally used as a phone pickup. The kind that uses suction to stick
to the phone, The article mentioned this type of system for
communication with cavers. Maybe that's what a "mole phone" is. But I
know hardly anything about electronics and have no idea if this would
work very well through salt or fresh water. I do remember reading that
the sound quality was good enough for voice but lacking for music. As
a scuba diver I can attest to how well sound travels through water. It
seems that an ultrasonic transducer mounted to the inside wall of a
stainless steel enclosure would work well. I'm sure false triggering
could be avoided the same way IR remotes work. The signal is modulated
at a certain frequency so the reciever pays attention to that. Maybe
the transducer could just be pulsed on and off at a certain frequency
to achieve the same thing.
ERS

Remove the ZZ from E-Mail address to contact me.