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.

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.

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

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