I want to make a simple transmitter to use as a locator beacon. But the
source would be in the ground (anywhere between 3 - 10ft). The receiver
would need to locate it, much like a metal detector would except it would be
a small hand-held "wand" with a LCD giving the direction and signal
strength.

I'm not sure of the signaling to use therefore I'm not sure of the antenna
required. But, it would need it to follow part 15 of the FCC
rules/regulations (none hazardous and allows required interference).

I am completely new at this sort of technology. I have created circuits
before using L555 timer, 4046Phase Loop, etc. But I've never went farther
than building simple demonstration circuits. I wondered if there was anyone
on this list that may be able to shed some light on what I would need and/or
how I would use them (a schematical description), or even point me to the
"yellow brick road".


Thanks!
--
//Clint Alexander

Clint Alexander wrote:
I want to make a simple transmitter to use as a locator beacon. But the
source would be in the ground (anywhere between 3 - 10ft). The receiver
would need to locate it, much like a metal detector would except it would be
a small hand-held "wand" with a LCD giving the direction and signal
strength.

Try burying a WiFi dongle and see what you get. 2.4gHz has the advantages
of being COTS (commercial off the shelf technology), easy to build
directional antennas, cheap and easily adapated to digital technology.

It also has the advantage of being legal in almost (if not) every country
in the world.

I'm not sure it will reach through 3-10 feet of dirt, but I expect that
anything much above 15khz will have that problem.

Geoff.


--
Geoffrey S. Mendelson, Jerusalem, Israel N3OWJ/4X1GM
New word I coined 12/13/09, "Sub-Wikipedia" adj, describing knowledge or
understanding, as in he has a sub-wikipedia understanding of the situation.
i.e possessing less facts or information than can be found in the Wikipedia.

On Jun 1, 4:44*pm, "Geoffrey S. Mendelson"
wrote:
Clint Alexander wrote:
I want to make a simple transmitter to use as a locator beacon. But the
source would be in the ground (anywhere between 3 - 10ft). The receiver
would need to locate it, much like a metal detector would except it would be
a small hand-held "wand" with a LCD giving the direction and signal
strength.

Try burying a WiFi dongle and see what you get. 2.4gHz has the advantages
of being COTS (commercial off the shelf technology), easy to build
directional antennas, cheap and easily adapated to digital technology.

It also has the advantage of being legal in almost (if not) every country
in the world.

I'm not sure it will reach through 3-10 feet of dirt, but I expect that
anything much above 15khz will have that problem.

Geoff.

--
Geoffrey S. Mendelson, Jerusalem, Israel *N3OWJ/4X1GM
New word I coined 12/13/09, "Sub-Wikipedia" adj, describing knowledge or
understanding, as in he has a sub-wikipedia understanding of the situation.

On Jun 1, 5:22*pm, UKMonitor wrote:
On Jun 1, 4:44*pm, "Geoffrey S. Mendelson"
wrote:





Clint Alexander wrote:
I want to make a simple transmitter to use as a locator beacon. But the
source would be in the ground (anywhere between 3 - 10ft). The receiver
would need to locate it, much like a metal detector would except it would be
a small hand-held "wand" with a LCD giving the direction and signal
strength.

Try burying a WiFi dongle and see what you get. 2.4gHz has the advantages
of being COTS (commercial off the shelf technology), easy to build
directional antennas, cheap and easily adapated to digital technology.

It also has the advantage of being legal in almost (if not) every country
in the world.

I'm not sure it will reach through 3-10 feet of dirt, but I expect that
anything much above 15khz will have that problem.

Geoff.

--
Geoffrey S. Mendelson, Jerusalem, Israel *N3OWJ/4X1GM
New word I coined 12/13/09, "Sub-Wikipedia" adj, describing knowledge or
understanding, as in he has a sub-wikipedia understanding of the situation.
i.e possessing less facts or information than can be found in the Wikipedia.

Try googling Avalanche / beacon / tranceiver / 457KHz

http://pistehors.com/backcountry/wik...e-Transceivers

UKM- Hide quoted text -

- Show quoted text -

Also Loc8tor

http://www.loc8tor.co.uk/Store/

UKM

UKMonitor wrote:
http://www.loc8tor.co.uk/Store/

I don't know what you are hiding, but some of the ELT (Emergency locator
transmitters) are tracked by satellite, and if you set one off sirens
go off in control centers.

Great if you are trying to get rescued, a disaster if you want to find
your "stash".

Geoff.

--
Geoffrey S. Mendelson, Jerusalem, Israel N3OWJ/4X1GM
New word I coined 12/13/09, "Sub-Wikipedia" adj, describing knowledge or
understanding, as in he has a sub-wikipedia understanding of the situation.
i.e possessing less facts or information than can be found in the Wikipedia.

On Jun 1, 10:21 am, "Clint Alexander" wrote:
I want to make a simple transmitter to use as a locator beacon. But the
source would be in the ground (anywhere between 3 - 10ft). The receiver
would need to locate it, much like a metal detector would except it would be
a small hand-held "wand" with a LCD giving the direction and signal
strength.

I'm not sure of the signaling to use therefore I'm not sure of the antenna
required. But, it would need it to follow part 15 of the FCC
rules/regulations (none hazardous and allows required interference).

I am completely new at this sort of technology. I have created circuits
before using L555 timer, 4046Phase Loop, etc. But I've never went farther
than building simple demonstration circuits. I wondered if there was anyone
on this list that may be able to shed some light on what I would need and/or
how I would use them (a schematical description), or even point me to the
"yellow brick road".

Thanks!
--
//Clint Alexander

Andy writes: I messed with a transmitter used to map out caves and
tunnels a while back and think that would fit your bill. I don't
remember the details
but I think it ran around 100 Khz or so, and the antenna was just a
coil
of wire about a foot in diameter, using magnetic near field coupling.
Power was only a few watts and the range was hundreds of feet.

If you google things like "cave mapping" , " spelunking
transmitters",
and keywords like that, you may have a lead to follow.

Good luck,

Andy W4OAH

On Jun 2, 12:35*am, AndyS wrote:
On Jun 1, 10:21 am, "Clint Alexander" wrote:





I want to make a simple transmitter to use as a locator beacon. But the
source would be in the ground (anywhere between 3 - 10ft). The receiver
would need to locate it, much like a metal detector would except it would be
a small hand-held "wand" with a LCD giving the direction and signal
strength.

I'm not sure of the signaling to use therefore I'm not sure of the antenna
required. But, it would need it to follow part 15 of the FCC
rules/regulations (none hazardous and allows required interference).

I am completely new at this sort of technology. I have created circuits
before using L555 timer, 4046Phase Loop, etc. But I've never went farther
than building simple demonstration circuits. I wondered if there was anyone
on this list that may be able to shed some light on what I would need and/or
how I would use them (a schematical description), or even point me to the
"yellow brick road".

Thanks!
--
//Clint Alexander
Andy writes: * *I messed with a transmitter used to map out caves and

tunnels a while back and think that would fit your bill. *I don't
remember the details
but I think it ran around 100 Khz or so, and the antenna was just a
coil
of wire about a foot in diameter, using magnetic near field coupling.
Power was only a few watts and the range was hundreds of feet.

* *If you google things like "cave mapping" *, " spelunking
transmitters",
and keywords like that, you may have a lead to follow.

* * * * * * Good luck,

* * * * * * *Andy W4OAH- Hide quoted text -

- Show quoted text -

At 457KHz they use ferrite rod antennas

I think if you are building your own system you need a crystal locked
transmitter and a very narrow bandwidth ( DSP filters ? ) receiver in
order to obtain the best range and rejection of unwanted noise and out
of band signals.

Some design notes can be found here.

http://www.ece.uvic.ca/~mblarows/ELE...ort%202-r1.pdf

http://www.backcountryaccess.com/eng...Future_000.pdf

Google or search US patent websites for 457KHZ transmitter antenna.

UKM

UKM

Clint Alexander Inscribed thus:

Consider just how big the antenna might have to be at those
frequencies. 300,000,000 divided by F in Hz = length in meters.
Using your 5Khz (300,000,000/5000) = 60,000 meters !



That's true. Okay -- I obviously would need a lower frequency

Lower frequencies mean longer antenna. :-(
Also since 5Khz is in the audio range of frequencies you might be better
off with a coil based microphone.

to penetrate ground; what would be a workable solution?

I think you need to do some more research. Its easier not to re-invent
the wheel.

What if I took 10ft of antennae and just coiled it so it didn't take
up so much space?

If you take any antenna and reduce its physical size you will also
reduce the amount of energy that it can radiate for any given input. I
forget the rule of thumb, but it goes something like inverse square.
Half the radiation quarter of the distance.


Thanks for all the info!

--
Best Regards:
Baron.

Lower frequencies mean longer antenna. :-(

Typo/Brain-fart -- I meant "higher" frequency


I think you need to do some more research. Its easier not to re-invent
the wheel.

I certainly do not wish to reinvent the wheel, but, I would like to carve
and sand my own wheel, though -- for commercial reasons.


I'm looking for the most lowest level of development that one could start
with given a humble work environment.

--


//Clint Alexander

"Baron" wrote in message
...
Clint Alexander Inscribed thus:

Consider just how big the antenna might have to be at those
frequencies. 300,000,000 divided by F in Hz = length in meters.
Using your 5Khz (300,000,000/5000) = 60,000 meters !



That's true. Okay -- I obviously would need a lower frequency

Lower frequencies mean longer antenna. :-(
Also since 5Khz is in the audio range of frequencies you might be better
off with a coil based microphone.

to penetrate ground; what would be a workable solution?

I think you need to do some more research. Its easier not to re-invent
the wheel.

What if I took 10ft of antennae and just coiled it so it didn't take
up so much space?

If you take any antenna and reduce its physical size you will also
reduce the amount of energy that it can radiate for any given input. I
forget the rule of thumb, but it goes something like inverse square.
Half the radiation quarter of the distance.


Thanks for all the info!

--
Best Regards:
Baron.

Clint Alexander Inscribed thus:


Lower frequencies mean longer antenna. :-(

Typo/Brain-fart -- I meant "higher" frequency


We all have them. :-)


I think you need to do some more research. Its easier not to
re-invent the wheel.

I certainly do not wish to reinvent the wheel, but, I would like to
carve and sand my own wheel, though -- for commercial reasons.


I've no problem with that ! But you do need to look at what work has
already been done by other people and try to understand what problems
they have had to overcome in order to achieve their goal. Then analyse
what you need to do to achieve your goal.


I'm looking for the most lowest level of development that one could
start with given a humble work environment.


Most entrepreneurs start of with an idea and develop it with very little
resources. But you have to ask the right questions and more important
understand the answers.

Radio propagation through the earth is one of the most challenging
problems you could attempt to solve. You seem to be concentrating on
very low frequencies, fine if you can tolerate very very slow data
flows. I'm sure there are frequencies that will propagate through the
earth fairly easily, but getting to a point where a usable signal
occurs with reliable results isn't easy.

Maybe more information about what you are trying to achieve would help
to point you in a better direction.


--
Best Regards:
Baron.