E/M radiation from a short vertical aerial
 

"Spike" wrote in message
...
Thanks for the comments, Jeff. Perhaps I'm not being clear enough.

Look at the issue this way.... While it's clear that the totality of the
e/m emissions from from the antenna depend on factors such as length,
height, and ground, (and I originally assumed a particular set-up in the
OP) there are three distinct methods by which such a transmission can be
received: the sky wave path to a distant receiver, a space wave to a
line-of-sight receiver (that could easily be outside the surface wave
range) and the surface wave to a receiver tucked into the far side of a
hill with no sky wave or space wave path. It can be expected that
increasing the transmit power will increase the received signal at all
three locations, but the question I'd like to see answered is: what
proportion of the power supplied to the antenna goes to each of these
three phenomena, which all arise every time the transmitter is keyed. They
might all be connected by the conditions you mention, I'm not suggesting
they aren't, but for the set-up I originally described, what are the
proportions of the power supplied to the antenna that contribute to each?

Or, to put it in yet another way...There might only be one 'wave' launched
from the set-up, that propagates in three different 'modes' (for the want
of a better word); so what controls the relative power/energy with which
each 'mode' is propagated?


You have to get it in your head there is not 3 differant waves launched from
the antenna. There is only one wave. As it leaves the antenna, whatever
the wave hits determins if it is ground, sky or whatever. The patern of the
antenna determins how much goes where.

With some antennas the patern is such much of it goes out to the horizon and
not much up in the air. Others radiate much to the vertical and not much
toward the horizon.

Think of it as throwing a rock into the middle a small pond. If there is
noting in the pond, the wave will go out toward the edges equally. If that
same rockis thrown in near the edge of the pond, some of the ripples will n
hit th eedge of the pond near the rock first while it will take some time
for the ripples to hit the other side.
You have the same origional wave, but its propogation is modified as to
where it is at . You do not have seperate waves leaving the rock.

E/M radiation from a short vertical aerial
 

Spike wrote:
On 07/03/15 01:49, wrote:
In rec.radio.amateur.antenna Spike wrote:

Imagine a short rod vertical aerial not connected to ground, for the
(say) 160/80/60/40m bands, as might be found in a typical /M set-up, fed
with RF energy and operating over ground of average conductivity.

Three different waves will be launched from this: the sky wave, the
space wave (including the reflected ray), and the surface wave. Each of
these have their own characteristics, inasmuch as the sky wave is
launched willy-nilly even if the band isn't open for that mode, the
space wave depends on the path to the receiver, and the surface wave
depends on the electromagnetic characteristics of the air and the
surface material, although to some extent the latter affects all the
waves generated.

These "waves" are actually called skywave and surface wave and are
a propagation phenomena.

See:

http://en.wikipedia.org/wiki/Skywave
http://en.wikipedia.org/wiki/Surface_wave
http://en.wikipedia.org/wiki/Line-of-sight_propagation

for how signals propagate.

Thanks to you and Jerry Stuckle for your replies.

Since a vertical aerial that I described initially emits all three of
these waves, I was interested in the relative amounts of the RF power
supplied to the antenna that goes into each. For example, does the sky
wave component take 90% of the power, leaving 10% for the space and
surface waves? What phenomena control this?


You've totally missed the point.

These "wave" phenomena are determined by the frequency and the condition
of the ionosphere, which is influenced by solar radiation.

A transmitting antenna knows nothing about any type of propagation.

The amount of any type of "wave" propagation that will happen depneds
on the antenna pattern, i.e. how much energy is radiated in any particular
direction, and the current ionospheric conditions.

There is a rule of thumb that says that maximum skywave occurs at an
antenna main lobe elevation of about 30 degrees, but it is only a
general rule of thumb. The exact angle will be determined by the
frequency and current condition of the ionosphere.



--
Jim Pennino

E/M radiation from a short vertical aerial
 

On 3/7/2015 6:13 AM, Spike wrote:
On 07/03/15 09:34, Jeff wrote:

Since a vertical aerial that I described initially emits all three of
these waves, I was interested in the relative amounts of the RF power
supplied to the antenna that goes into each. For example, does the sky
wave component take 90% of the power, leaving 10% for the space and
surface waves? What phenomena control this?

You are missing the point Spike, the antenna has no knowledge of how the
power that it radiates will propagate. It all depends on how much power
leaves the antenna at what angle, and what angle the antenna is
positioned relative to ground.

All the antenna has is a polar response of how much power is radiated at
what angle. It is that angle and the way the atmosphere reacts at any
particular time that controls the propagation of waves. This can vary
with time of day etc.

What controls the polar diagram is the physical dimensions of the
antenna, the height above ground, the conductivity of the ground, the
proximity of other objects, and other factors.

Thanks for the comments, Jeff. Perhaps I'm not being clear enough.

Look at the issue this way.... While it's clear that the totality of the
e/m emissions from from the antenna depend on factors such as length,
height, and ground, (and I originally assumed a particular set-up in the
OP) there are three distinct methods by which such a transmission can be
received: the sky wave path to a distant receiver, a space wave to a
line-of-sight receiver (that could easily be outside the surface wave
range) and the surface wave to a receiver tucked into the far side of a
hill with no sky wave or space wave path. It can be expected that
increasing the transmit power will increase the received signal at all
three locations, but the question I'd like to see answered is: what
proportion of the power supplied to the antenna goes to each of these
three phenomena, which all arise every time the transmitter is keyed.
They might all be connected by the conditions you mention, I'm not
suggesting they aren't, but for the set-up I originally described, what
are the proportions of the power supplied to the antenna that contribute
to each?

Or, to put it in yet another way...There might only be one 'wave'
launched from the set-up, that propagates in three different 'modes'
(for the want of a better word); so what controls the relative
power/energy with which each 'mode' is propagated?

The case I'm particularly interested in is the short-rod vertical not
connected to ground, in the MF/low-HF bands, as might be found in a /M
set-up.

What you are not grasping is that these "modes" of transmission have
*nothing* to do with the antenna really. As others have said, the
antenna only transmits different signal strengths in different
directions. How much power sent in a given direction is only loosely
connected to how much power ends up in these different reception modes
if at all.

The real issue is what do you expect to do with these numbers if you
have them? I expect that any equations you find for received signal
strength will already factor in these relative values giving a received
signal strength as a function of *total* power radiated from the antenna.

Are you trying to compare the effectiveness of different antenna for
different receiving modes?

--

Rick

E/M radiation from a short vertical aerial
 

On Friday, March 6, 2015 at 7:31:12 PM UTC-6, Jerry Stuckle wrote:

That depends entirely on the radiation pattern of the antenna. For
instance, the sky wave will be that part of the pattern which has fairly
high angle of radiation (but lower than the space wave), and the surface
wave will have a very low angle of radiation.

The space wave will be quite low angle if working from one point
on the earth to another point on the earth. Strictly speaking, a
space wave could be at any angle, if you include talking from the
earth to someone in space. Earth to ISS is space wave.
The signals one receives from a local VHF/UHF FM radio or TV station
are space wave. Two CB'ers talking to each other 5 miles apart are
using space wave. Only in the case of the earth dweller talking to
someone in space, or on the moon, etc would be using a space wave
at a higher angle than the usual angle needed for sky wave.

And on the high HF bands like 10m, in some cases the angles used
for skywave can be fairly low if working DX.
But those angles would still likely be a bit higher than terrestrial
earth to earth space wave communication.

True ground wave, which to me, is the same as the surface wave,
actually can follow the curvature of the earth, which a space wave
cannot do. But true ground or surface waves are generally only
taken advantage of on the lower frequencies such as MW, or LW.

But they can be used likely as high as say the 40m band in some
cases. I used to have a fairly stout ground wave on 40m when I
ran a high ground plane. And I think part of that energy was acting
as a surface wave and following the curvature of the earth.
The reason I think so, is because the distances I could work with it
were a good bit farther than what I would expect with the space wave
alone.
And I could use the space and surface wave in that case, no matter
what time of day or night, or regardless of the conditions needed for
sky wave between the two locations. So lots of times during the day
when the MUF dropped low enough to lose those people who were 100-150
miles away via sky wave, I was still able to work them via the ground
wave. The people using the dipoles and such could hardly hear a peep
out of the ones I was working in those cases.


And BTW - don't worry about the trolls who have no idea what they are
talking about - but insist on showing their ignorance, anyway.

We sure wouldn't want to have any of that, now would we.. :/

E/M radiation from a short vertical aerial
 

On Saturday, March 7, 2015 at 6:17:18 PM UTC-6, wrote:

But they can be used likely as high as say the 40m band in some
cases. I used to have a fairly stout ground wave on 40m when I
ran a high ground plane. And I think part of that energy was acting
as a surface wave and following the curvature of the earth.
The reason I think so, is because the distances I could work with it
were a good bit farther than what I would expect with the space wave
alone.

BTW, I could have been fooled a bit by refraction.. It is possible
for the space wave to go a bit farther than actual line of sight,
being as the radio horizon is a bit farther than the visual horizon.
Sometimes as much as a third the distance farther.
So it's hard to tell for sure which was which on 40m..
True surface wave propagation is great on MW in the daytime..
Night too, except that it's covered up by skywave clutter.. :/
My MW loops were good for receiving that, and I could totally null
out a ground/surface wave signal if I felt so compelled.

E/M radiation from a short vertical aerial
 

On 08/03/15 00:17, wrote:

True ground wave, which to me, is the same as the surface wave,
actually can follow the curvature of the earth, which a space wave
cannot do. But true ground or surface waves are generally only
taken advantage of on the lower frequencies such as MW, or LW.

That's true, which is a shame as useful ground-wave/surface wave can be
had on 28 MHz; a maximum range figure for a path over ground of average
conductivity might be 25 miles, and considerably more if the path is
over water (especially sea-water).

But they can be used likely as high as say the 40m band in some
cases. I used to have a fairly stout ground wave on 40m when I
ran a high ground plane. And I think part of that energy was acting
as a surface wave and following the curvature of the earth.

The reason I think so, is because the distances I could work with it
were a good bit farther than what I would expect with the space wave
alone.

Maximum surface wave over ground with average conductivity might be 40
to 45 miles on 40m; if you were getting ranges over this, then your
ground conductivity might have been enhanced, or due to the height of
your ground-plane, you could have experienced refraction of the space
wave. If your location was on a hill-top or other high ground, this
could have helped the space wave refraction as well.

And I could use the space and surface wave in that case, no matter
what time of day or night, or regardless of the conditions needed for
sky wave between the two locations. So lots of times during the day
when the MUF dropped low enough to lose those people who were 100-150
miles away via sky wave, I was still able to work them via the ground
wave. The people using the dipoles and such could hardly hear a peep
out of the ones I was working in those cases.

I believe that the availability 24/7/365 of the space-wave and
surface-wave is one of Amateur Radio's undervalued assets. On 160m the
surface wave might reach over 100 miles, including behind hills and into
valleys, which here in the UK would enable a station to reach a
significant proportion of the UK Amateur population. Unfortunately,
people dismiss verticals in favour of horizontals of one form or
another, the usefulness of which drops to zero when the sky wave
disappears (apart from any vertically-polarized radiation from a
mismatched feeder or unbalanced elements).

Thanks for your interesting observations.

--
Spike

"Hard cases, it has frequently been observed, are apt to introduce bad
law". Judge Rolfe

E/M radiation from a short vertical aerial
 

On 07/03/15 15:57, Ralph Mowery wrote:
"Spike" wrote

Or, to put it in yet another way...There might only be one 'wave' launched
from the set-up, that propagates in three different 'modes' (for the want
of a better word); so what controls the relative power/energy with which
each 'mode' is propagated?

You have to get it in your head there is not 3 differant waves launched from
the antenna. There is only one wave. As it leaves the antenna, whatever
the wave hits determins if it is ground, sky or whatever. The patern of the
antenna determins how much goes where.

With some antennas the patern is such much of it goes out to the horizon and
not much up in the air. Others radiate much to the vertical and not much
toward the horizon.

Think of it as throwing a rock into the middle a small pond. If there is
noting in the pond, the wave will go out toward the edges equally. If that
same rockis thrown in near the edge of the pond, some of the ripples will n
hit th eedge of the pond near the rock first while it will take some time
for the ripples to hit the other side.
You have the same origional wave, but its propogation is modified as to
where it is at . You do not have seperate waves leaving the rock.

Thanks for the explanation and illustration.

Amateur (and professional) literature abounds with terms like sky wave,
space wave, and surface wave. There are sky wave radars, space wave
radars, and surface wave radars, for example. It isn't unreasonable to
use these as descriptors of what I was trying to find out. This was, to
recap, the relative proportions of the RF power delivered to the aerial
for each of these (whatever one wants to call them), for a typical /M
(mobile) set-up on the MF and low HF bands operating over ground of
average conductivity, a near everyday occurrence in the Amateur
community. The mechanism for the single wave that's transmitted
resulting in (whatever one wants to call them) isn't really of interest,
but the relative proportions that wind up in (whatever one wants to
call them) are.

In terms of your analogy, the rock being thrown into the pool close to
one edge of the pond is the equivalent of the short rod /M aerial
operating close to the ground, mounted on the vehicle. I can imagine
that if the edge of the pond is a gentle sandy slope, the reflected
waves will be different in nature that if the edge of the pond is a
vertical rock. However, this is merely reflecting the different ground
conductivities that might be experienced in the real-life Amateur
situation: some energy will go skywards to a distant receiver, some will
travel through air to a line-of-sight receiver, and some will go to a
receiver in the shadow of a hill that cannot receive either of the other
two (whatever one wants to call them).

--
Spike

"Hard cases, it has frequently been observed, are apt to introduce bad
law". Judge Rolfe

E/M radiation from a short vertical aerial
 

On 08/03/15 09:33, Jeff wrote:
Spike wrote

I think you are coming at this from the wrong view point.

Perhaps the question that you should be asking is what take-off angles
are required to produce maximum ground wave, and how do you maximize
that for a MF mobile installation.

I'm really after figures for the proportions of the RF power fed to that
antenna, that finish up in whatever 'they' are called (the use of the
well-known word 'waves' seem to upset people despite their having been
used for the specifics I mentioned, for about 100 years).

I'm aware that reconfiguring the set-up might affect these proportions,
but I did refer the original query to a typical /M (mobile) set-up of a
short rod antenna not connected to ground and operating over average
conductivity in the MF/low-HF bands.

For example, does 40% power the sky (redacted), another 40% power the
space (redacted), and the other 20% power the surface (redacted)?
Clearly, 100% of the RF power goes somewhere, and the various parts of
it must add up to 100% - so what are the proportions?

If the /M (mobile) set-up was changed to a /P (portable) one with a 5/8
lambda ground-mounted antenna, the sky (redacted) proportion would lower
and the surface/space (redacted) would increase - but from what to what?

I'm beginning to think that this topic is either so simple or so complex
that most Amateurs have either forgotten it or have never heard of it.

--
Spike

"Hard cases, it has frequently been observed, are apt to introduce bad
law". Judge Rolfe

E/M radiation from a short vertical aerial
 

Spike wrote:

On 08/03/15 09:33, Jeff wrote:
Spike wrote

I think you are coming at this from the wrong view point.

Perhaps the question that you should be asking is what take-off angles
are required to produce maximum ground wave, and how do you maximize
that for a MF mobile installation.

I'm really after figures for the proportions of the RF power fed to that
antenna, that finish up in whatever 'they' are called (the use of the
well-known word 'waves' seem to upset people despite their having been
used for the specifics I mentioned, for about 100 years).

I'm aware that reconfiguring the set-up might affect these proportions,
but I did refer the original query to a typical /M (mobile) set-up of a
short rod antenna not connected to ground and operating over average
conductivity in the MF/low-HF bands.

For example, does 40% power the sky (redacted), another 40% power the
space (redacted), and the other 20% power the surface (redacted)?
Clearly, 100% of the RF power goes somewhere, and the various parts of
it must add up to 100% - so what are the proportions?

If the /M (mobile) set-up was changed to a /P (portable) one with a 5/8
lambda ground-mounted antenna, the sky (redacted) proportion would lower
and the surface/space (redacted) would increase - but from what to what?

I'm beginning to think that this topic is either so simple or so complex
that most Amateurs have either forgotten it or have never heard of it.

I suspect that the sort of precision with which one can measure signal
strength. plus very local variations of surface wave intensity due to
varying ground conditions, mean that it would be hard to know if the
signal level resulted from, say, one, five or fifty percent of the
transmitted power. So I suspect your question has never been answered.
An opportunity for some collaborative research between local amateurs?


--
Roger Hayter

E/M radiation from a short vertical aerial
 

"Spike" wrote in message
...
On 08/03/15 09:33, Jeff wrote:
Spike wrote

I think you are coming at this from the wrong view point.

Perhaps the question that you should be asking is what take-off angles
are required to produce maximum ground wave, and how do you maximize
that for a MF mobile installation.

I'm really after figures for the proportions of the RF power fed to that
antenna, that finish up in whatever 'they' are called (the use of the
well-known word 'waves' seem to upset people despite their having been
used for the specifics I mentioned, for about 100 years).

I'm aware that reconfiguring the set-up might affect these proportions,
but I did refer the original query to a typical /M (mobile) set-up of a
short rod antenna not connected to ground and operating over average
conductivity in the MF/low-HF bands.

For example, does 40% power the sky (redacted), another 40% power the
space (redacted), and the other 20% power the surface (redacted)? Clearly,
100% of the RF power goes somewhere, and the various parts of it must add
up to 100% - so what are the proportions?

If the /M (mobile) set-up was changed to a /P (portable) one with a 5/8
lambda ground-mounted antenna, the sky (redacted) proportion would lower
and the surface/space (redacted) would increase - but from what to what?

I'm beginning to think that this topic is either so simple or so complex
that most Amateurs have either forgotten it or have never heard of it.


I think that Jeff may be on to something. What you need to do is download
one of the antenna modeling programs. Set it up for the antenna type you
want. Then you can look at the patten and see the take off angle. The take
off angle is what determins the ammount of power you have the differant
types of propogation.