ELF radio needs more watts than MW radio?

[Benj]

On Aug 2, 4:24 am, Wim Lewis <w...@hhhh.org> wrote:

In article <haurl5-jtg....@mail.specsol.com>, <j...@specsol.spam.sux.com> wrote:
In sci.physics kronec...@yahoo.co.uk wrote:
You have never heard of the inverse square law obviously. High
frequencies are line of site only and can go long distances
because you pump out more power. You need to compare apples with
apples.

The inverse square law applies to isotropic radiators. No real world
RF antenna is an isotropic radiator.

The inverse square law applies to anisotropic radiators, too.

I know this is a Radium thread so I hesitate....but you guys are
REALLY in need of a radio engineer!

Yes, the inverse square law applies to anisotropic radiators as well
IN THE FAR FIELD REGION!

In the "near field" or what some here have suggested is the "faster
than light" region it doesn't apply.

VLF transmissions tend to bend around the earth which is one reason
they are useful for long distances and found exclusive use in the
early days of radio. Higher frequencies (so-called "short wave" ) were
discovered to bounce off the ionosphere (more or less) and thus
achieved popularity later for long distance transmission using that
bounce. Higher frequencies are not reflected back so longer distances
are harder to achieve. But this does now mean that over the horizon
transmissions are not possible. The high frequency waves tend to be
scattered by diffraction sending energy down below the horizon. This
is the way that certain over the horizon radars (DEW line) work. But
since most of the energy is NOT scattered, HUGE amounts of power are
needed.

So.... What if we had just ONE photon at a frequency of ONE Hz, how
much carrier power would be needed? Would it be less than the DEW
radar? What if that one photon were single sideband?

 

[John Larkin]

On Sat, 2 Aug 2008 02:08:03 -0700 (PDT), Benj <bjacoby@iwaynet.net>
wrote:

On Aug 2, 4:24 am, Wim Lewis <w...@hhhh.org> wrote:
In article <haurl5-jtg....@mail.specsol.com>, <j...@specsol.spam.sux.com> wrote:
In sci.physics kronec...@yahoo.co.uk wrote:
You have never heard of the inverse square law obviously. High
frequencies are line of site only and can go long distances
because you pump out more power. You need to compare apples with
apples.

The inverse square law applies to isotropic radiators. No real world
RF antenna is an isotropic radiator.

The inverse square law applies to anisotropic radiators, too.

I know this is a Radium thread so I hesitate....but you guys are
REALLY in need of a radio engineer!

Yes, the inverse square law applies to anisotropic radiators as well
IN THE FAR FIELD REGION!

In the "near field" or what some here have suggested is the "faster
than light" region it doesn't apply.

VLF transmissions tend to bend around the earth which is one reason
they are useful for long distances and found exclusive use in the
early days of radio. Higher frequencies (so-called "short wave" ) were
discovered to bounce off the ionosphere (more or less) and thus
achieved popularity later for long distance transmission using that
bounce. Higher frequencies are not reflected back so longer distances
are harder to achieve. But this does now mean that over the horizon
transmissions are not possible. The high frequency waves tend to be
scattered by diffraction sending energy down below the horizon. This
is the way that certain over the horizon radars (DEW line) work. But
since most of the energy is NOT scattered, HUGE amounts of power are
needed.

So.... What if we had just ONE photon at a frequency of ONE Hz, how
much carrier power would be needed? Would it be less than the DEW
radar? What if that one photon were single sideband?

You are REALLY in need of a physicist!

1 photon per second at 1 Hz is a power level of 6e-34 watts. Somewhat
less than the DEW line transmitters.

Single-photon SSB is meaningless.

John

 

[Benj]

On Aug 2, 11:25 am, j...@specsol.spam.sux.com wrote:

The inverse square law applies to isotropic radiators. No real world
RF antenna is an isotropic radiator.
The inverse square law applies to anisotropic radiators, too.

So you are saying a perfectly collimated beam follows the inverse
square law?

Yes, he is, Jim! And the reason for that is because a "perfectly
collimated" beam simply does not exist!

Even in the case of a single mode TEM 00 Gausian beam laser, the
radiation spreads out in the far field. One can arrange things so
that the narrow "waist" of the output beam occurs at a distance from
the laser, and that beam SEEMS to not follow the inverse square
relationship, but the fact is as I pointed out above, the seeming
failure is due to being in what is essential the "near field" of the
beam. At a great enough distance the beam expands.

 

[John Larkin]

On Sat, 02 Aug 2008 18:55:06 GMT, jimp@specsol.spam.sux.com wrote:

In sci.physics Benj <bjacoby@iwaynet.net> wrote:
On Aug 2, 11:25?am, j...@specsol.spam.sux.com wrote:

The inverse square law applies to isotropic radiators. No real world
RF antenna is an isotropic radiator.
The inverse square law applies to anisotropic radiators, too.

So you are saying a perfectly collimated beam follows the inverse
square law?

Yes, he is, Jim! And the reason for that is because a "perfectly
collimated" beam simply does not exist!

It certainly does mathematically.

Not for a beam made of waves.

Even in the case of a single mode TEM 00 Gausian beam laser, the
radiation spreads out in the far field. One can arrange things so
that the narrow "waist" of the output beam occurs at a distance from
the laser, and that beam SEEMS to not follow the inverse square
relationship, but the fact is as I pointed out above, the seeming
failure is due to being in what is essential the "near field" of the
beam. At a great enough distance the beam expands.

If you want to talk practical, it is practical to generate a beam
that over the distances of interest is collimated well enough that
the inverse square law does not strictly apply.

Most real microwave links are that way.

Never heard of the Radar Equation? Or done a microwave link budget?

John

 

[Timo A. Nieminen]

On Sat, 2 Aug 2008, jimp@specsol.spam.sux.com wrote:

In sci.physics Benj <bjacoby@iwaynet.net> wrote:
On Aug 2, 11:25?am, j...@specsol.spam.sux.com wrote:

The inverse square law applies to isotropic radiators. No real world
RF antenna is an isotropic radiator.
The inverse square law applies to anisotropic radiators, too.

So you are saying a perfectly collimated beam follows the inverse
square law?

Yes, he is, Jim! And the reason for that is because a "perfectly
collimated" beam simply does not exist!

It certainly does mathematically.

Not even then, if the beam is required to have finite energy flux [1] and
be a solution of the Helmholtz equation (or even the paraxial wave
equation).

I think a better phrasing of your original point would have been "The
inverse square law applies to the far field of a radiator." Don't like the
inverse square law? Stay in the near field, where beams can be collimated
rather than becoming spherical waves, or you can get faster than 1/r^2
fall-off from higher-order multipole sources.

But while many (including myself) are picking on the details, your
original point that high frequencies can allow highly directive
transmission is spot on. Also the point made by another that the
Earth-ionosphere waveguide avoids the inverse square law too. Tough luck
for the frequencies in the middle - all they're good for is broadcast
transmission when you want more bandwidth than you're allowed at the lower
frequencies.

[1] Infinite energy flux can deliver unto you infinite plane waves and
Bessel beams, which are perfectly collimated, but not physically
realisable.

--
Timo

 

[John Larkin]

On Sat, 02 Aug 2008 21:35:04 GMT, jimp@specsol.spam.sux.com wrote:

In sci.physics John Larkin <jjlarkin@highnotlandthistechnologypart.com> wrote:
On Sat, 02 Aug 2008 18:55:06 GMT, jimp@specsol.spam.sux.com wrote:

In sci.physics Benj <bjacoby@iwaynet.net> wrote:
On Aug 2, 11:25?am, j...@specsol.spam.sux.com wrote:

The inverse square law applies to isotropic radiators. No real world
RF antenna is an isotropic radiator.
The inverse square law applies to anisotropic radiators, too.

So you are saying a perfectly collimated beam follows the inverse
square law?

Yes, he is, Jim! And the reason for that is because a "perfectly
collimated" beam simply does not exist!

It certainly does mathematically.

Not for a beam made of waves.

What part of "mathematically" are you having trouble understanding?

Even in the case of a single mode TEM 00 Gausian beam laser, the
radiation spreads out in the far field. One can arrange things so
that the narrow "waist" of the output beam occurs at a distance from
the laser, and that beam SEEMS to not follow the inverse square
relationship, but the fact is as I pointed out above, the seeming
failure is due to being in what is essential the "near field" of the
beam. At a great enough distance the beam expands.

If you want to talk practical, it is practical to generate a beam
that over the distances of interest is collimated well enough that
the inverse square law does not strictly apply.

Most real microwave links are that way.

Never heard of the Radar Equation? Or done a microwave link budget?

Yes, and many, many times.

What I have never done is have occasion to use the inverse square law
in an RF link calculation.

And you ignore distance?

(Microwave, not RF)

John

 

[Don Bowey]

On 8/2/08 2:08 AM, in article
d475cb99-1c06-456f-8f29-23a84a7834d6@d77g2000hsb.googlegroups.com, "Benj"
<bjacoby@iwaynet.net> wrote:

On Aug 2, 4:24 am, Wim Lewis <w...@hhhh.org> wrote:
In article <haurl5-jtg....@mail.specsol.com>, <j...@specsol.spam.sux.com
wrote:
In sci.physics kronec...@yahoo.co.uk wrote:
You have never heard of the inverse square law obviously. High
frequencies are line of site only and can go long distances
because you pump out more power. You need to compare apples with
apples.

The inverse square law applies to isotropic radiators. No real world
RF antenna is an isotropic radiator.

The inverse square law applies to anisotropic radiators, too.

I know this is a Radium thread so I hesitate....but you guys are
REALLY in need of a radio engineer!

Yes, the inverse square law applies to anisotropic radiators as well
IN THE FAR FIELD REGION!

In the "near field" or what some here have suggested is the "faster
than light" region it doesn't apply.

VLF transmissions tend to bend around the earth which is one reason
they are useful for long distances and found exclusive use in the
early days of radio. Higher frequencies (so-called "short wave" ) were
discovered to bounce off the ionosphere (more or less) and thus
achieved popularity later for long distance transmission using that
bounce. Higher frequencies are not reflected back so longer distances
are harder to achieve. But this does now mean that over the horizon
transmissions are not possible. The high frequency waves tend to be
scattered by diffraction sending energy down below the horizon. This
is the way that certain over the horizon radars (DEW line) work. But
since most of the energy is NOT scattered, HUGE amounts of power are
needed.

I was on the Dew line Extension project in the Aleutians and worked with the
tropo radios, etc. Five Watts (the exciter) into a 60 foot parabolic
antenna gave us usable communications at 100+ miles, with occasional
frequent deep fades. Twenty-five kW got rid of the fade effects.

So.... What if we had just ONE photon at a frequency of ONE Hz, how
much carrier power would be needed? Would it be less than the DEW
radar? What if that one photon were single sideband?

 

[Sjouke Burry]

jimp@specsol.spam.sux.com wrote:

In sci.physics John Larkin <jjlarkin@highnotlandthistechnologypart.com> wrote:
On Sat, 02 Aug 2008 18:55:06 GMT, jimp@specsol.spam.sux.com wrote:

In sci.physics Benj <bjacoby@iwaynet.net> wrote:
On Aug 2, 11:25?am, j...@specsol.spam.sux.com wrote:
The inverse square law applies to isotropic radiators. No real world
RF antenna is an isotropic radiator.
The inverse square law applies to anisotropic radiators, too.
So you are saying a perfectly collimated beam follows the inverse
square law?
Yes, he is, Jim! And the reason for that is because a "perfectly
collimated" beam simply does not exist!
It certainly does mathematically.

Not for a beam made of waves.

What part of "mathematically" are you having trouble understanding?
Math and nature sometimes fit nicely together, but are not the same.

Any "REAL" beam does not have a 100% math description.
To do that you have to know it all, and only trolls claim such.
So your perfect beam does not exist.
Of course you can think of one, you can almost make one, but in the
end all math used in describing the real world is an approximation.

All beams have some divergence, and somewhat obey the inverse
square law.
Just try and aim any laserbeam on a target 3 miles away, and you
will find out.
Did that once, to make a "really" straight path at a 3 mile airfield.
At 3 miles the laserbeam was about 3-6 yards diameter, and moving
all over the place,because a mathematically rigid beam also does
not exist.

 

[Jasen Betts]

On 2008-08-02, jimp@specsol.spam.sux.com <jimp@specsol.spam.sux.com> wrote:

In sci.physics Benj <bjacoby@iwaynet.net> wrote:
On Aug 2, 11:25?am, j...@specsol.spam.sux.com wrote:

The inverse square law applies to isotropic radiators. No real world
RF antenna is an isotropic radiator.
The inverse square law applies to anisotropic radiators, too.

So you are saying a perfectly collimated beam follows the inverse
square law?

Yes, he is, Jim! And the reason for that is because a "perfectly
collimated" beam simply does not exist!

It certainly does mathematically.

only if it has infinite width.

consider the difraction that when your perfectly collimated beam passes
through an aperature that exactly matches its size

contrast that with what happens when it doesn't.

Bye.
Jasen

 

[Edward Green]

On Jul 24, 8:31 pm, "Green Xenon [Radium]" <glucege...@gmail.com>
wrote:

Hi:

I remember reading somewhere than ELF [Extremely Low Frequency] radio
transmission is inefficient because it requires to much power.

If that is the case, wouldn't MW [Medium Wave] radio transmission
require even more power?

MW and ELF are forms of electromagnetic radiation in the RF spectrum.

An photon [or electromagnetic wave] of a higher-frequency has more
energy than a photon of a lower-frequency.

Let's say there are there are two radio transmitters, one emits 2 GHz
waves while the other emits 2 kHz waves. If the two radio transmitters
use the same modulation scheme [AM/FM, etc.] and emit the same amount
of photons-per-second-per-square-meter, the 2 GHz transmitter will be
using more watts than the 2 kHz transmitter -- because a 2 GHz photon
requires more power to generate than a 2 kHZ photon. Right?

So how would transmitting a lower-frequency radio wave require more
power than transmitting a higher-frequency radio wave?

The problem seems to be, assuming photons have something to do with
it: in particular, the energy of photons. If what you say is true, it
would be a purely classical effect: ELF waves are larger than higher
frequency waves, and it is _plausible_ that they need proportionally
more power to excite a larger region of space to have a sufficient
number of waves to support a signal.

I didn't say that is necessarily true, but it has a better chance of
being true than your argument about photons.

 

[Edward Green]

On Jul 25, 12:28 am, "Spaceman" <space...@yourclockmalfunctioned.duh>
wrote:

wrote:
Hi:

I remember reading somewhere than ELF [Extremely Low Frequency] radio
transmission is inefficient because it requires to much power.

True and not true.
Maybe this will help shed some ELF light on the subject.http://en.wikipedia.org/wiki/Extremely_low_frequency

Congratulations. Out of messages 2-7 in this thread, yours was the
first which at least tried to contribute some constructive
information, instead of a random insult: that is, unless "bullshit",
"snip crap" and "doesn't know what he is talking about" now constitute
constructive information when written by approved posters.

Geez... I'm beginning to sound like Tom Potter -- but you guys should
be ashamed of yourselves. The Wikipedia article does mention some
efficiency issues, and you could have discussed whether these were
intrinsic to any use of ELF, or just to the transmitting stations used
by the USN.

Of course the issue of photon energy seems like a completely misguided
idea... although it _might_ have been nice to discuss whether there
were any basis for the implicit idea of "constant information per
carrier photon", or not -- and why.

Since when does being on the right side of most discussions (let's say
for the sake of argument) justify churlish, not to say loutish,
behavior. You gentlemen can contribute much more than that. There
are other readers besides the OP.

 

[Edward Green]

On Jul 27, 8:27 am, cliff wright <c.c.wri...@paradise.net.nz> wrote:

BTW I've always wondered what sort of
antenna the sub uses for reception? I bet that's still classified perhaps?

http://publications.drdo.gov.in/gsdl/collect/defences/index/assoc/HASH01ec/da9eb1dc.dir/doc.pdf

contains some interesting looking pictures.

 

[Benj]

On Aug 3, 2:17 pm, Edward Green <spamspamsp...@netzero.com> wrote:

Since when does being on the right side of most discussions (let's say
for the sake of argument) justify churlish, not to say loutish,
behavior.  You gentlemen can contribute much more than that.  There
are other readers besides the OP.

Come on! This was a "Radium" question! If you don't know that that
means "open season", then search the archives a bit!

OK. We are all properly admonished. NOW!!! How about we start
discussing the "Jewish Question" !!!!

 

[Edward Green]

On Jul 27, 12:35 pm, j...@specsol.spam.sux.com wrote:

In sci.physics Michael Black <et...@ncf.ca> wrote:

Which you get when you drop the other sideband, and instant  halving
of the bandwidth used.
There is nothing inherently narrow bandwidth about SSB. It does
tend to be narrow because you are mostly transmitting only voice,
and that doesn't take up much bandwidth.  And it was certainly
easier to restrict bandwdith with SSB, since in the early days
those phasing methods were so limited that they couldn't deal
with wide bandwidth, and it's easier to make a crystal filter
that is narrow than wide.

Non sequitur.

First you say it is an instant half the bandwidth, then you say there
is nothing inherently narrow about it.

You can't have it both ways.

Makes sense to me. It's like saying that cutting a suit down the
middle makes an instantly more narrow suit, but that there is nothing
inherently narrow about a half-suit: it could be half a size 58, vs. a
child's size.

 

[Benj]

On Aug 3, 1:05 pm, j...@specsol.spam.sux.com wrote:

In sci.physics Jasen Betts <ja...@xnet.co.nz> wrote:



On 2008-08-02, j...@specsol.spam.sux.com <j...@specsol.spam.sux.com> wrote:
In sci.physics Benj <bjac...@iwaynet.net> wrote:
On Aug 2, 11:25?am, j...@specsol.spam.sux.com wrote:

The inverse square law applies to isotropic radiators. No real world
RF antenna is an isotropic radiator.
The inverse square law applies to anisotropic radiators, too.

So you are saying a perfectly collimated beam follows the inverse
square law?

Yes, he is, Jim!  And the reason for that is because a "perfectly
collimated" beam simply does not exist!

It certainly does mathematically.
only if it has infinite width.

Which is quite possible mathematically.

consider the difraction that when your perfectly collimated beam passes
through an aperature that exactly matches its size
contrast that with what happens when it doesn't.
Bye.
   Jasen

Concider what happens when the perfectly collimated beam impacts a
half gallon of Chunky Monkey ice cream.

However, I'm not sure what either has to do with a wave front propogating
in free space.

Has everything to do with it. Mathematics is not "reality". In the
real world, things are not "infinite" or "point sources" or other
mathematical concepts. So for the most part this argument is stupid.
But you were the one saying that the inverse square law did not apply
to an anisotropic beam. We say it pretty much did at a distance. Then
you say only at "infinity" and then we have to answer how close of an
approximation to reality do you want your math to be? So you say how
far if not infinity? Astronomical distances? And we say "could be",
and we note the distance needed is that which takes you into the "far
field" of the source. So how far away is that? Well how large is the
source? If the source is "infinite" then a "perfectly collimated"
beam is mathematically possible. But who cares since "infinite
objects" are not possible. All you are doing is arguing how many
angels can stand on the head of a pin!

The bottom line is all of this is that radiation sources creating
propagating radiation can be replaced by an "equivalent aperture" at
some point and as noted, an aperture source actually has a transform
relationship between the aperture "source" and the propagating beam.
At a sufficient distance the expansion of the beam is always dictated
by those mathematics. Hence all arguments of "collimated beams" not
following inverse square laws at some location is invalid. The
questions of how closely are the laws followed or how far you have to
be away are merely practical fine points. It is your "natural
philosophy" that were are taking issue with here.

 

[Timo A. Nieminen]

On Sat, 2 Aug 2008, jimp@specsol.spam.sux.com wrote:

The geometry of the inverse square law is predicated upon radiation
from a point source.

Worse than that, you only get exact inverse square behaviour for a
monopole point source. Given that there are no electromagnetic wave
monopole point sources ...

The field from a real radiator approaches following the inverse
square law as the distance increases such that the divergence
approaches that of a point source.

Given a good enough beam former, that distance may become an astronomical
distance.

The collimating characteristics of many antennas are such that you can
not be on this planet and be far enough away to have enough divergence
to approximate inverse square law behavior.

This is helped by us not having to be very far from the surface of the
planet to not be on the planet. For practical beams, it's hard to get the
distance to being really "astronomical", even at optical frequencies.

This thread is such a splendid example of a usenet tempest-in-a-teacup!

--
Timo

 

[Edward Green]

On Aug 3, 2:34 pm, Benj <bjac...@iwaynet.net> wrote:

On Aug 3, 2:17 pm, Edward Green <spamspamsp...@netzero.com> wrote:

Since when does being on the right side of most discussions (let's say
for the sake of argument) justify churlish, not to say loutish,
behavior.  You gentlemen can contribute much more than that.  There
are other readers besides the OP.

Come on! This was a "Radium" question! If you don't know that that
means "open season", then search the archives a bit!

<snip provocative material>

Ok. So it was my chance to feel morally superior for a second for
standing up for the underdog.

But really, to the extent there was a serious response, you might hope
it would center on power requirements for transmitting a given measure
of information, with some particular attention to the role of the
radio frequency used (how's _that_ for a 19th century title?).
Instead, it was a catalyst for a series of "I am more cleverer than
you"'s about side-bands...

 

[Edward Green]

On Aug 2, 6:35 pm, j...@specsol.spam.sux.com wrote:

In sci.physics Timo A. Nieminen <t...@physics.uq.edu.au> wrote:



On Sat, 2 Aug 2008, j...@specsol.spam.sux.com wrote:
In sci.physics Benj <bjac...@iwaynet.net> wrote:
On Aug 2, 11:25?am, j...@specsol.spam.sux.com wrote:

The inverse square law applies to isotropic radiators. No real world
RF antenna is an isotropic radiator.
The inverse square law applies to anisotropic radiators, too.

So you are saying a perfectly collimated beam follows the inverse
square law?

Yes, he is, Jim!  And the reason for that is because a "perfectly
collimated" beam simply does not exist!

It certainly does mathematically.
Not even then, if the beam is required to have finite energy flux [1] and
be a solution of the Helmholtz equation (or even the paraxial wave
equation).
I think a better phrasing of your original point would have been "The
inverse square law applies to the far field of a radiator." Don't like the
inverse square law? Stay in the near field, where beams can be collimated
rather than becoming spherical waves, or you can get faster than 1/r^2
fall-off from higher-order multipole sources.
But while many (including myself) are picking on the details, your
original point that high frequencies can allow highly directive
transmission is spot on. Also the point made by another that the
Earth-ionosphere waveguide avoids the inverse square law too. Tough luck
for the frequencies in the middle - all they're good for is broadcast
transmission when you want more bandwidth than you're allowed at the lower
frequencies.
[1] Infinite energy flux can deliver unto you infinite plane waves and
Bessel beams, which are perfectly collimated, but not physically
realisable.
--
Timo

Most reasonable response yet.

The geometry of the inverse square law is predicated upon radiation
from a point source.

The field from a real radiator approaches following the inverse
square law as the distance increases such that the divergence
approaches that of a point source.

Given a good enough beam former, that distance may become an astronomical
distance.

The collimating characteristics of many antennas are such that you can
not be on this planet and be far enough away to have enough divergence
to approximate inverse square law behavior.

To my ignorant brain, there would seem to be two reasonable meanings
to "inverse square law behavior".

One would be that you are sufficiently far from the source that the
intensity of radiation is well approximated by an inverse square law
through a full solid angle.

The other would be that you were at a distance from the (collimated)
source such that the intensity of radiation was well approximated by
the inverse square law _over a partial solid angle_ : for example, so
that the radiation pattern were well approximated by a cone.

It's not clear to me if all sources have an inverse square law regime
in the first sense for _any_ distance : can we get sufficiently far
from a laser, for example, that it appears equally bright through a
full solid angle, even behind the laser?

The answer to this question would seem to be "no", for the following
reason: a perfect laser, or collimated monochromatic beam, would
apparently have a distribution of photon momenta containing only one
value of wave vector k. Obviously no real beam can have this property
(for one thing, it would be a plane wave filling all of space, not a
collimated beam with finite cross section anywhere). BUT, it is not
necessary for photons to be emitted in this unphysical way in order
for the answer to the question to be "no": it is only necessary for
them to have some distribution which is _not_ uniform in solid angle!
This non-uniformity in solid angle will persist to all distances, so
the general source will never appear to be a point source, no matter
how far we back up from it: at least not in the sense of radiating
equally through a full solid angle. Instead, the far field intensity
will have the limiting form:

f(phi,psi)/r^2

Am I correct, or am I all screwed up (with appropriate details,
please .

 

[Edward Green]

On Aug 3, 3:17 pm, "christofire" <christof...@btinternet.com> wrote:

Well one sixteenth of a wavelength is pretty close to uniform in my book!
All antennas exhibit some sort of phase centre, although for some it may
appear diffuse when inspected at close range, but at distances further than
that practical yardstick the deviation from a perfect spherical wave is
small enough to be found _utterly insignificant_ in practice.  Indeed, it
follows that practical antennas do behave _sufficiently_ like point sources
when inspected from a distance (>2D^2/lambda), albeit
not-necessarily-isotropic ones.

Aha! My idle amateur speculations are corroborated by somebody who at
least does a convincing simulation of an expert.

I have the feeling there was some confusion in this thread between a
point source and an isotropic point source, and which one was implied
when "inverse square law" was mentioned.

<...>

Please let this disagreement rest now.  I have tried hard to retain
objectivity but I fear if this branch to this thread is taken further along
the same lines my objectivity may give way to facetiousness.

That is admirable restraint.

 

[jmfbahciv]

Benj wrote:

On Aug 3, 2:17 pm, Edward Green <spamspamsp...@netzero.com> wrote:

Since when does being on the right side of most discussions (let's say
for the sake of argument) justify churlish, not to say loutish,
behavior. You gentlemen can contribute much more than that. There
are other readers besides the OP.

Come on! This was a "Radium" question! If you don't know that that
means "open season", then search the archives a bit!

Shit happens. Use it as fertilizer and be productive.

OK. We are all properly admonished. NOW!!! How about we start
discussing the "Jewish Question" !!!!

/BAH