E/M radiation from a short vertical aerial
 

On 08/03/15 20:06, wrote:
On Sunday, March 8, 2015 at 3:40:21 AM UTC-5, Spike wrote:

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).

That's space wave on 10m.

Not in the UK! Even the flatlands of Norfolk and Lincolnshire have
enough surface topography to make space-wave unlikely.

I used to work local 10m all the time back in the 80's, early 90's..
25 miles is fairly easy with any decent antenna, at a decent height
above ground. I used to work a good bit farther than that fairly often,
when using an antenna at 35-45 feet up.

The ground is good here, and the ground plane was full size at 36 ft
at the base of the antenna. But it may well have been an enhanced space
wave. I was often working well over 100 miles away in such a case.

I'd go for space-wave with refraction or tropo ducting, for these sorts
of ranges.

Well, not everyone does. I know many on 160m who favor verticals.
Not only for ground wave, but better DX.

Not in the UK... We have a progressive licensing system here, in which
most people never progress at all. The level they qualify at is more
concerned with how to fit mains plugs - something that isn't required
here as moulded plugs have been compulsory for 20 years. These people
tend to buy the one aerial they've heard of, the G5RV.

The ground wave is pretty good on 160m if using a vertical.
Nearly as good as on the MW AM broadcast band, being the two bands
are right next door to each other, so to speak.

I'm a big fan of 160m ground wave/surface wave.

--
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 in message
...
Not in the UK... We have a progressive licensing system here, in which
most people never progress at all. The level they qualify at is more
concerned with how to fit mains plugs - something that isn't required here
as moulded plugs have been compulsory for 20 years.

WHS

And the tragedy is that even those who pass at the highest level
can show no technical acumen whatsoever, to the extent that on Usenet
they join in sneering but without ever understanding any of the technical
content. We have one such person over in uk.radio.amateur who is currently
being shunned for his infantile outbursts of ignorance.

E/M radiation from a short vertical aerial
 

"Spike" wrote in message
...

What I'm after is the relative amounts of power that finish up at the
ionosphere, travelling through the atmosphere, and travelling along the
surface, for a typical mobile set-up.


Which is, after all, quite a reasonable line of enquiry for any
self-respecting _REAL_ radio amateur, but perhaps the thread has
developed in an unfortunate direction because of the characterisitics
of questions posed off-the-cuff and not as a reasoned thesis?

(I know that I have fallen iinto that trap on a number of occasions)

E/M radiation from a short vertical aerial
 

Spike wrote:

On 08/03/15 18:08, Jeff wrote:

Spike, you seem to think that there are different components coming from
the antenna that make up the sky-wave component and the ground wave.
That is not correct the antenna only radiates one kind of wave (EM).
Whether it finds its way to the receiver by sky-wave or ground wave is
purely due to what angle the wave hits the atmosphere/ground, and the
state of the atmosphere.

As an Example take a transmission on top band; during the day normally
there will be virtually no sky-wave propagation; use exactly the same
set up during the night and there will be considerable sky-wave.

I think I knew that, Jeff...

If your question is what do you have to do to maximize the ground wave
the it is obviously to keep the maxima in the polar diagram as low as
possible and don't waste power shooting it at high angles.

No, I know how to do that. What I'm after is the relative amounts of
power that finish up at the ionosphere, travelling through the
atmosphere, and travelling along the surface, for a typical mobile set-up.

Of course that is easier said than done, particularly with a mobile
where the ground is likely to be poorer than a fixed station with a good
ground mat.

My initial conditions were a ground of average conductivity.

Using something like NEC to model antennas will show the effects of
various antenna configurations and ground configurations on the low
angles of radiation.

But it's only a model, and results depend on how it was constructed.

I would rephrase your original question as follows. The approximate
signal strength of the space wave at a certain distance, assuming a
fairly low angle of the main lobe of the aerial with a moderate amount
of gain over isotropic, can be calculated from simple physics. At
about the same distance (and where of course you are not likely to see
the space wave unless you have a very tall pole, but it has a defined
signal strength well above you), what is the likely signal strength of
the ground wave? Is it very much lower due to poor coupling, losses
etc.? Is it about the same? Or is it much higher due to some
phenomenon which I can't explain at the moment? That is really the
same question as the one you asked (I think!), but couched in practical
and testable terms.

(It is rather trying to see the ignorant mocking a perfectly reasonable
question from a position of total incomprehension. A bit juvenile,
methinks.)

--
Roger Hayter

E/M radiation from a short vertical aerial
 

Stephen Thomas Cole wrote:

rickman wrote:
On 3/8/2015 4:17 PM, Stephen Thomas Cole wrote:

Spike, you're a gormless ****. Seriously, you're giving Gareth Alun Evans
G4SDW a run for his money here.

I can see you are right in the running yourself...

Hey, I'm not the one with the fundamental misunderstanding of radio theory
after 50+ years in the hobby.

There is no "fundamental misunderstanding" unless it be yours. At
worst, loose phraseology.

--
Roger Hayter

E/M radiation from a short vertical aerial
 

On 09/03/2015 06:26, Stephen Thomas Cole wrote:
rickman wrote:
On 3/8/2015 4:17 PM, Stephen Thomas Cole wrote:

Spike, you're a gormless ****. Seriously, you're giving Gareth Alun Evans
G4SDW a run for his money here.

I can see you are right in the running yourself...

Hey, I'm not the one with the fundamental misunderstanding of radio theory
after 50+ years in the hobby.


Nor do you spend your time putting done newcomers and claiming only the
route you claim to have followed into the hobby was the right one.

E/M radiation from a short vertical aerial
 

"Spike" wrote in message
...

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. (etc)
__________

Below is a link to a NEC study showing the 1.9 MHz fields radiated by a
3-meter vertical monopole driven against 4 x 2-meter horizontal radials,
where the entire assembly is elevated 9" above earth of average
conductivity. This might approximate a mobile installation of a whip
antenna mounted on a vehicle, except for the pattern distortions produced by
the body of the vehicle.

Radiation from this system at elevation angles other than near zero degrees
could act as direct waves, space waves or skywaves, depending on propagation
paths, propagation conditions, and the physical locations of receive
antennas.

http://s20.postimg.org/ipzwlc9kd/Fie...t_Vertical.jpg

R. Fry

E/M radiation from a short vertical aerial
 

On 3/9/2015 3:29 AM, Jeff wrote:

I've been lurking in this thread and it reminded me of a time many years
ago when I was working on a receiver setup. A colleague gave me a book
with an equation for signal strength of a signal in the cell phone
frequency range in various terrestrial environments. I had a little
trouble accepting an arbitrary equation that wasn't at least close to
the typical 1/r^2 formula in free space. I seem to recall there was no
1/r^2 term at all rather it was more like a linear or maybe had a
rlog(r) term.

In any event, no one could explain where the equation came from. I
suppose it was an empirical equation rather than something derived from
theory. Ignoring waves bounced off the upper atmosphere, I assume the
earth acts to help focus the signal and strengthen it close to the
ground?


You are correct, most of those formulas are empirical, base on actual
observations. Look up papers by Egli and by Hatta, they will five you
some idea on how theses formulas were derived.

Jeff

As are basically all formulas. Even Ohm's Law was derived from actual
observations.

Although Einstein's equations such as E=mc^2 wasn't derived from actual
observation, it did come by projection of existing knowledge by an
exceptional mind.

--
==================
Remove the "x" from my email address
Jerry, AI0K

==================

E/M radiation from a short vertical aerial
 

Roger Hayter wrote:
Stephen Thomas Cole wrote:

rickman wrote:
On 3/8/2015 4:17 PM, Stephen Thomas Cole wrote:

Spike, you're a gormless ****. Seriously, you're giving Gareth Alun Evans
G4SDW a run for his money here.

I can see you are right in the running yourself...

Hey, I'm not the one with the fundamental misunderstanding of radio theory
after 50+ years in the hobby.

There is no "fundamental misunderstanding" unless it be yours. At
worst, loose phraseology.


I suggest you re-read Spike's multiple, confused posts about all the
different types of waves that pour forth from an antenna.

--
STC // M0TEY // twitter.com/ukradioamateur

E/M radiation from a short vertical aerial
 

rickman wrote:
On 3/9/2015 2:26 AM, Stephen Thomas Cole wrote:
rickman wrote:
On 3/8/2015 4:17 PM, Stephen Thomas Cole wrote:

Spike, you're a gormless ****. Seriously, you're giving Gareth Alun Evans
G4SDW a run for his money here.

I can see you are right in the running yourself...

Hey, I'm not the one with the fundamental misunderstanding of radio theory
after 50+ years in the hobby.

The problem has nothing to do with radio theory.

No, you're right. It's to do with Spike's stupidity.

--
STC // M0TEY // twitter.com/ukradioamateur