On Sunday, March 8, 2015 at 3:40:21 AM UTC-5, Spike wrote:
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).

That's space wave on 10m. Even seeing a surface wave on 40m is a bit
of a stretch from the norm. As I mentioned in my 2nd post, the reason
I saw farther than expected from space wave operation on 40m, could
well have been due to refraction of the space wave, and due to the fact
that the radio horizon is farther than the visual horizon.

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 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.

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 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).

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

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

That's space wave on 10m. Even seeing a surface wave on 40m is a bit
of a stretch from the norm. As I mentioned in my 2nd post, the reason
I saw farther than expected from space wave operation on 40m, could
well have been due to refraction of the space wave, and due to the fact
that the radio horizon is farther than the visual horizon.

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 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.

The ground is good here,

With respect, the difference in local ground is rather over stated.

Taking the US as an example, the conductivity ranges from 0.5mS to 30mS,
which sounds a lot. However, compared to sea water, 5000mS, it is all
rather poor.

I noticed this some years back when reading a paper, as I recall written
by the US Navy, which played down the importance of ground conductivity,
other when either at sea or in close proximity to the shore.

There is a world atlas of conductivity which is on the web, I can't
recall the URL, but it is worth looking out. The various seas and oceans
do vary, I recall the Baltic being less conductive for example.
Likewise, some of the patterns in the various countries are rather
intriguing. Some areas you would expect to be conductive are not. I
assume due to local rock formations etc.

On 3/8/2015 7:21 PM, Brian Reay wrote:

There is a world atlas of conductivity which is on the web, I can't
recall the URL, but it is worth looking out. The various seas and oceans
do vary, I recall the Baltic being less conductive for example.
Likewise, some of the patterns in the various countries are rather
intriguing. Some areas you would expect to be conductive are not. I
assume due to local rock formations etc.

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?

--

Rick

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

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

On 3/9/2015 10:11 AM, Jeff wrote:


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


That is certainly not correct in a lot of cases. The inverse square law
for free space path loss, for example, is derived intuitively and simply
from the transmitted power being equally distributed in all directions,
not from observations.

S= P*(1/(4piD^2))

Jeff

Jeff,

Actually, not. It was observed first back in the 1700's-1800's when the
link between electricity and magnetism was being investigated. And
hundreds of years before that, it was a know property of magnets.

The equations didn't come until later.

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

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

On 09/03/15 15:43, Jerry Stuckle wrote:
On 3/9/2015 10:11 AM, Jeff wrote:


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


That is certainly not correct in a lot of cases. The inverse square law
for free space path loss, for example, is derived intuitively and simply
from the transmitted power being equally distributed in all directions,
not from observations.

S= P*(1/(4piD^2))

Jeff

Jeff,

Actually, not. It was observed first back in the 1700's-1800's when the
link between electricity and magnetism was being investigated. And
hundreds of years before that, it was a know property of magnets.

The equations didn't come until later.


You are confusing a magnetic field with an EM field. You can have a
magnetic field with no E field- eg from a bar magnet. It will have a
magnet field which exhibits the inverse square law but no E field.

On 3/9/2015 12:54 PM, Brian Reay wrote:
On 09/03/15 15:43, Jerry Stuckle wrote:
On 3/9/2015 10:11 AM, Jeff wrote:


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


That is certainly not correct in a lot of cases. The inverse square law
for free space path loss, for example, is derived intuitively and simply
from the transmitted power being equally distributed in all directions,
not from observations.

S= P*(1/(4piD^2))

Jeff

Jeff,

Actually, not. It was observed first back in the 1700's-1800's when the
link between electricity and magnetism was being investigated. And
hundreds of years before that, it was a know property of magnets.

The equations didn't come until later.


You are confusing a magnetic field with an EM field. You can have a
magnetic field with no E field- eg from a bar magnet. It will have a
magnet field which exhibits the inverse square law but no E field.



Brian,

No, I'm not confusing the two. But my point is that one led to the
other. The equations didn't appear out of mid air - measurements
preceded them.

The observations I was talking about in the 1700's-1800's were for EM
fields. And my point was their loss with distance is the same as with M
fields - which had been known for a much longer time.

And E fields were also measured back in the days of Leyden jars and the
like.

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

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

On 3/9/2015 12:54 PM, Brian Reay wrote:
On 09/03/15 15:43, Jerry Stuckle wrote:
On 3/9/2015 10:11 AM, Jeff wrote:


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


That is certainly not correct in a lot of cases. The inverse square law
for free space path loss, for example, is derived intuitively and simply
from the transmitted power being equally distributed in all directions,
not from observations.

S= P*(1/(4piD^2))

Jeff

Jeff,

Actually, not. It was observed first back in the 1700's-1800's when the
link between electricity and magnetism was being investigated. And
hundreds of years before that, it was a know property of magnets.

The equations didn't come until later.


You are confusing a magnetic field with an EM field. You can have a
magnetic field with no E field- eg from a bar magnet. It will have a
magnet field which exhibits the inverse square law but no E field.

The problem would seem to be that there is confusion with an equation
being preceded by measurements (pretty much *every* equation known) with
equations that were crafted in the absence of derivation solely to fit
data. Even Einstein's equations had measurements that preceded them and
were essential to their formulation. Michelson and Morley made the
measurements that set the stage for E=Mc^2. I would hardly call that an
empirical equation.

Not much point in trying to discuss this. It will be impossible to find
any common ground I am sure.

--

Rick

On Sunday, March 8, 2015 at 6:21:06 PM UTC-5, Brian Reay wrote:

The ground is good here,

With respect, the difference in local ground is rather over stated.

Maybe so, but not really by me. :|

Taking the US as an example, the conductivity ranges from 0.5mS to 30mS,
which sounds a lot. However, compared to sea water, 5000mS, it is all
rather poor.

Sure. It's rated at 30mS here, which was why I said it was "good".
And I'm about 55-60 miles from the Gulf of Mexico. I've run mobile from the
beach, one time actually backing up to the water and running ground wires
into the ocean. Needless to say, my 14 ft tall mobile whip was browning
the food quite nicely on that occasion. On the Ford truck it was on,
it does pretty well even over poor ground, but it really got with the
program down at the beach. I was parked at the mouth of the Brazos River
down at Quintana Beach. I was also fishing.. I'd rig up my rod and reels,
putting them on auto pilot, and then would kick back and drink brewed
beverages while jibber jabbering on the radio. Mostly 40 and 80 meters.
If I saw a rod start to twitch, I'd put down the mike and adult beverage,
and reel in the fish.


I noticed this some years back when reading a paper, as I recall written
by the US Navy, which played down the importance of ground conductivity,
other when either at sea or in close proximity to the shore.

I've never really worried about it too awful much. I don't really rely
on it, one way or the other. Even with decent ground quality, I still
run a good radial set, or if elevated, enough radials to do the job,
as if the ground were poor. Of course, I can't control the ground
conductivity away from my QTH. So no use worrying about it.


There is a world atlas of conductivity which is on the web, I can't
recall the URL, but it is worth looking out. The various seas and oceans
do vary, I recall the Baltic being less conductive for example.
Likewise, some of the patterns in the various countries are rather
intriguing. Some areas you would expect to be conductive are not. I
assume due to local rock formations etc.

The only map I've seen is one that is in the ARRL handbooks.. It's the
one that shows this area as 30 mS. I think it only covered the US, or
maybe North America at the max.. Don't know about the rest of the planet.

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