Baron wrote:

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.

That's not true. All the power delivered to an antenna is either
radiated or turned into heat -- antennas have to obey the law of
conservation of energy like everything else. The fraction which is
turned into heat is determined by the loss of the antenna, not its
physical size. Loss does generally increase as the size gets smaller,
but not by any fixed proportion to the size, and many small antennas can
be quite efficient.

Roy Lewallen, W7EL

On Jun 1, 2:48*pm, JIMMIE wrote:
On Jun 1, 11:21*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

Your friend the 555 may be just what you need. I will oscillate up to
around half a megacycle and have harmonics from DC to daylight.

Jimmie

On the other hand an EM antenna may not best suit your job. I would
suggest feeding a buried coil and let this be half of a transformer
coupled to your receiver.

Jimmie

In article ,
Baron wrote:

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.

It might be worth checking out some of the work done by Bonnie Crystal
KQ6XA and her cohorts. They've been able to communicate from the
earth's surface, down into caves (and back up), using LF and HF radio
systems.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Baron wrote:

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.
. . .

Attenuation through the ground depends on the soil conductivity and
dielectric constant, and the frequency. Here's the attenuation in dB/ft
for two ground types and a number of frequencies:

Freq MHz Avg soil(1) Vy good soil(2)
0.01 0.037 0.091
0.1 0.12 0.29
1 0.35 0.90
10 0.66 2.4
100 0.69 3.3
10,000 0.69 3.4

(1) Conductivity = 0.005 S/m, dielectric constant = 13
(2) Conductivity = 0.03 S/m, dielectric constant = 20

So the distance you can communicate depends on these factors as well as
antenna efficiency, power, and receiver sensitivity.

Attenuation in salt water is very much higher, which is why submerged
submarines have to communicate at VLF.

Roy Lewallen, W7EL

Roy Lewallen wrote:
Attenuation through the ground depends on the soil conductivity and
dielectric constant, and the frequency. Here's the attenuation in dB/ft
for two ground types and a number of frequencies:

Freq MHz Avg soil(1) Vy good soil(2)
0.01 0.037 0.091
0.1 0.12 0.29
1 0.35 0.90
10 0.66 2.4
100 0.69 3.3
10,000 0.69 3.4

So if I get this right, a 2.4gHz signal in normal soil would be anttenuated
6.9 db (less than 2 "S units). In very good soil, it would be anttenuated
around 34 db, which would make it difficult to receive.

A Pringles can antenna has a gain of about 18db, that would certainly be
enough for average soil, and might be good enough for very good soil.

It also has the advantage of possibly being a 2 way link.

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.

Baron wrote:
Clint Alexander Inscribed thus:

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

It would be for plotting tunnels from gopher, rabbits, etc. But I
don't want to buy COTS, I want to grab all the components myself, put
the circuits together on a few breadboards and make my own casing for
it.

What's important is finding the simple components needed to implement
this type of operation. I've read into ELTs and MELs (Miner Emergency
Locator) as well, and while I have found a few circuit diagrams, they
did not show what antenna is being used and/or how that was connected
to the circuit.

Here is a good example. If I use this oscillator:
http://yhst-27389313707334.stores.ya...1kto68pro.html
(Voltage adjustable from 1KHz to 68MHz)

If we set this to work off of 1-5KHz:
A) How would I figure out what antenna is needed to send this signal
through 10-20ft of dirt and concrete?
B) Where on a circuit would this antenna be attached? (directly
connected to the oscillator and 9-12V with perhaps a resistor
in-between?)

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 !


for subsurface comms and this sort of application, you typically use a
loop antenna, and accept the terrible efficiency of a physically small
antenna.

Look at the radios used by cavers for communication.

Geoffrey S. Mendelson wrote:
Roy Lewallen wrote:
Attenuation through the ground depends on the soil conductivity and
dielectric constant, and the frequency. Here's the attenuation in dB/ft
for two ground types and a number of frequencies:

Freq MHz Avg soil(1) Vy good soil(2)
0.01 0.037 0.091
0.1 0.12 0.29
1 0.35 0.90
10 0.66 2.4
100 0.69 3.3
10,000 0.69 3.4

So if I get this right, a 2.4gHz signal in normal soil would be anttenuated
6.9 db (less than 2 "S units). In very good soil, it would be anttenuated
around 34 db, which would make it difficult to receive.

Those dB values are correct for 10 feet of homogeneous soil. Real soil
is stratified, and reflections from layer boundaries could have some
pretty profound effects. 6.9 dB is from 2 to 4 "S-Units" on my Icom,
depending on where on the S meter scale it is.

A Pringles can antenna has a gain of about 18db, that would certainly be
enough for average soil, and might be good enough for very good soil.

Relative to what? According to this site
http://www.turnpoint.net/wireless/has.html, a Pringles can antenna
showed about the same gain as a Lucent omnidirectional antenna. Of
course, an 18 dB error is only a mis-estimation of power density by a
factor of 1,000,000,000,000,000,000. Pah, piddly nit-picking details.
You could make it up by increasing the power by the same factor.

It also has the advantage of possibly being a 2 way link.

A reliable one would take some calculation, planning, and a realistic
idea of antenna performance.

Roy Lewallen, W7EL

For all involved in the thread -- here's a perfect example. Sondes are
locator systems used in many areas (I think) such as pipelines:
http://www.rjmcompany.com/Pipe-cable...0-SuperCAT.htm

These have frequencies of 512hz, 8Khz and 33Khz

I'm searching for any specs now regarding crystal and antenna for both
transmitter and receiver. But I'm certain that the antenna isn't 1000's of
meters long

If I'm reading this right -- I would want to build my own version of the
technology rather than purchase theirs'.

--


//Clint Alexander

"Clint Alexander" wrote in message
news
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

On Jun 3, 12:53*am, "Clint Alexander" wrote:
For all involved in the thread -- here's a perfect example. Sondes are
locator systems used in many areas (I think) such as pipelines:http://www..rjmcompany.com/Pipe-cabl...0-SuperCAT.htm

These have frequencies of 512hz, 8Khz and 33Khz

I'm searching for any specs now regarding crystal and antenna for both
transmitter and receiver. But I'm certain that the antenna isn't 1000's of
meters long

If I'm reading this right -- I would want to build my own version of the
technology rather than purchase theirs'.

--

//Clint Alexander

"Clint Alexander" wrote in message

news


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- Hide quoted text -

- Show quoted text -

I think we need to know a bit more about your application.

I have one of these pipe / cable locators, you need to have a good
idea of the route the pipework its taking and then 'sweep' the
approximate area with the end of the locator. If you don't have a
starting point it's very time consuming to cover a large area.

The avalanche beacon permits initial detection over a much wider area
which considerably speeds up a 'blind' search.

What size transmitter (physical) are you able to use, Max weight,
Battery duration, required detection radius, depth of burial etc.

UKM

The relationship is so close, I would suggest that the Sonde is a perfect
application for my needs.

Like I said previously, I want to build my own version. So we'll assume this
as the target technology leaving me with the question of what antenna would
be needed to perform these operations. I suppose the oscillator is just a
simple crystal or perhaps even voltage controlled (adjustable). I can use a
555 for this....



--


//Clint Alexander

"UKMonitor" wrote in message
...
On Jun 3, 12:53 am, "Clint Alexander" wrote:
For all involved in the thread -- here's a perfect example. Sondes are
locator systems used in many areas (I think) such as
pipelines:http://www.rjmcompany.com/Pipe-cable...0-SuperCAT.htm

These have frequencies of 512hz, 8Khz and 33Khz

I'm searching for any specs now regarding crystal and antenna for both
transmitter and receiver. But I'm certain that the antenna isn't 1000's of
meters long

If I'm reading this right -- I would want to build my own version of the
technology rather than purchase theirs'.

--

//Clint Alexander

"Clint Alexander" wrote in message

news


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- Hide quoted text -

- Show quoted text -

I think we need to know a bit more about your application.

I have one of these pipe / cable locators, you need to have a good
idea of the route the pipework its taking and then 'sweep' the
approximate area with the end of the locator. If you don't have a
starting point it's very time consuming to cover a large area.

The avalanche beacon permits initial detection over a much wider area
which considerably speeds up a 'blind' search.

What size transmitter (physical) are you able to use, Max weight,
Battery duration, required detection radius, depth of burial etc.

UKM