Propagation of Medium Wave E-M Radiation

Reminds me of my Navy days when they tried to tell an amateur radio operator that VHF was "always" line of sight.

When I talked about AM medium wave being a "ground wave" phenomona I of course overlooked the nightime sitch when sky waves might happen.

However, nightime skywaves have nothing to do with raised antennas.

True?

I recall posting a theory along the lines of:

Maybe the tiny AM signal is being reflected off the bottom of utility lines? Where utility lines could be producing a simulated sky wave (bounce) effect, maybe...?

and being followed by:

According to what I understand medium wave radio (the AM band) is a ground wave service.

The signal follows the top of the ground. ...(snip)the best result is obtained by minimizing the impedence to ground, by bringing everything flat down to earth level(/snip)...

Then me following with:

AM (BCB) Does indeed follow the conture of the earth.

The only reason for the height of a commercial AM Broadcast tower is to allow for a proper vertical antenna.

______________

However I do agree with the fact that skywaves are produced at AM broadcast frequencies, if for no other reason, simply because a station 1000 miles away from me wipes my little flea powered signal out nearing sunset and until after sunrise. The same station is not even detectable during daylight hours.

Hence my original theory...

Maybe the tiny AM signal is being reflected off the bottom of utility lines? Where utility lines could be producing a simulated sky wave (bounce) effect, maybe...?

Although I didn't communicate my thoughts very well, what I meant to say is something along the lines of "Perhaps my antenna being underneath the power lines is producing something similar to skywave (or skip) effect -except that it is occurring- during the daylight hours -instead of the nighttime hours (which would seem impossible for my theory to work at night since that strong signal from 1000 miles away is going to overpower it anyhow, but the utility lines seem to be producing an artificial nighttime condition during the day)." or something along those lines.

But the way I see it, everyone is correct and right on target with the subject matter at hand. Especially given the small amount of data I provided in the original comment.

I'll quit before i trip over my tongue anymore.

Well, I need to add (again) before I quit...
I believe that Carl was correct about my theory being not so much the case, with the actual case being that I had minimized the path of resistance.

Hats off to all of you. 🙂

The notion of an artificial sky-wave caused by power lines has never been advanced as a possible event.

I'll sit back while the bigger brains come in here to affirm or debunk that idea.

The transmitted fields of an unlicensed AM station compliant with FCC §15.219 might couple into nearby conductors including a-c power lines both inside and outside various structures, the ground wires leading down the sides of wooden poles used to carry the utility lines distributing a-c power, metal poles used to support street lights, metal flagpoles, etc.

For vertically-oriented transmit antennas, coupling is greater into such vertical conductors than horizontal ones.

Much of that coupled energy will re-radiate from those conductors over their lengths, but the re-radiated fields are weaker than the fields arriving at those conductors, and their useful range is limited to locations very close to those re-radiators.

The reflected signals from vertical reflectors located in the transmission field are sometimes out-of-phase with the originating signal thus cause cancelations at certain locations.

I see such cancelations and ghosting outside of what I consider my usable range. I also see it briefly where the utilities leave the sky and enter an underground system (inside of usable range).

On the transmitter side of the underground utility service entrance there is a cancellation on the road, but pull off the road on either side, and the signal is there... from the overhead wires on one side, it seems... and from either the house wiring or the true signal on the other side of the road (where utility lines are underground).

Another similar ghosting effect occurs where the underground system ends/terminates... There isn't any cancellation at that point, but there is an echo (ghosting), as if there were two out of sync transmitters overlapping one another. This (ghosting) seems to be limited to an area of a spot about 30 foot wide by 150 foot the best I can estimate.

Now on to the other side of the underground utilities...
About another 30 some feet, the signal is once again strong and very listenable, a good quality signal that seems to follow the electrical lines to a roadway junction, then briefly cancels out--the signal following a turn along a highway more than following the side roads--which (side roads) are more near the transmitter, but the signal follows the main road strongly...
cancellation?, I have to assume.

So I assumed that the utility lines in conjunction with nearby creeks was somehow producing an artificial skip or skywave during the daylight hours.

I like to think about it by comparing it to a ball bouncing.
Maybe more like multiple balls bouncing along the same path.
The cancellations being corners of a room that the balls are bouncing around.

Nothing (antenna wise) is physically connected to utility lines.

If I locate the transmitter inside, the effect goes away and the range is severely decreased.

When the transmitter is above the power lines, the range is extended, but isn't as rich, full, or bold sounding. It becomes unstable and mostly unusable after a few hundred foot. It's there, but I wouldn't listen to it.

When placed at near ground level, outdoors, the range very usable.

I'm not going to claim that "artificial skip" is being produced by ground to utility-line bounce, but it sure appears as if this might be happening during the daylight hours.

As Carl has already pointed out to me, the impedance to ground has been greatly reduced, and that in itself has undoubtedly improved the range.
All of my other observations may be purely coincidental.

Again I want to stress that I am not claiming anybody wrong.

It is already hard enough to grasp radio theory and accepted real world conditions without the likes of me introducing a theory of "artificial skip".

What I have described here could be a common occurrence.
I don't believe that "Carrier Current" as we know it is at play.
I believe some form of useful re-radiation is at play, but I don't understand why or even how it's usability seems to be way above typical.

Right now I'm having a mental block sorting out the difference between sky wave and skip wave. I guess they mean the same thing.

If the vertical signal travels the ground, how does it get up to the sky?

If the signal radiates from a vertical antenna, how does it end up in horizontal power lines?

What about dense clouds? Do they cause some AM skip?

What about the chemtrail spreading of aluminum and other metalic particulates into the upper atmosphere as part of the military's experiment in weather control?

When I walk down the porch stairs with my portable radio, holding the metal railing boosts the signal on my radio which is in the other hand.

When I leave the neighborhood by car my AM signal is gone after 3-blocks, but at the intersection 6-blocks away it comes in again strong enough to stop and listen... blocking four way traffic.

I've been listening today with my AM5000 turned back to 36mW, yet the signal is full-scale all around the house and yard.

I am not ready to debunk "artificial skip" as an idea. It seems reasonable and probably even happens from high wet trees.

The way I understand it, AM Carriers produce both ground and sky waves.
When the conditions are right, those sky waves bounce back down.

My definition of skip is when conditions make it favorable for the sky wave to bounce down, then back up, and then back down... abnormally of what they can (or should) be predicted to do.

As for dense clouds, and using today for an example, I have received a Canadian station all day long, where the channel would usually be clear during the day. So I think the dense clouds are producing the skip, or if skip is even the correct word for extended daytime propagation.
Come to think of it, the word "skip" may be some CB jargon that I picked up years ago...and have began to use it generically to describe "favorable propagation conditions for distant communication at relatively low power".

So if we consider that the signal has the ability to bounce off from the sky (i don't remember what layer of the ionosphere comes into play during night, nor do I remember the layer that limits propagation during the day(or do I have this backwards???) Seems like I faintly remember a level E and maybe a level C, but...) it is rather safe to assume that the signal bounces off from the ground at the very least.

Assuming the signal (or wave) has enough power, it reaches the sky and bounces back to earth.

Our Part 15 units are limited in this sense, as they really don't produce enough power to bounce back, least not with detectable levels.
So our range is limited to the ground-wave combined with the initial bounce up towards the sky.

What I believe I'm seeing and trying to describe is the effect of an accidental placement of the transmitter and antenna within a "sweet spot" that allows that initial bounce up into the air to bounce back from utility lines.

I don't know exactly how the wave would be bouncing back up, striking the lines again, and then bouncing back down, repeatedly (skipping).
Unless it has to do with those steel underground irrigation lines...hummm...

It is beyond my knowledge, but I believe this is taking place.

Oh me my goodness, it turns out there are a mess of spheres, including a mesosphere. Check em out:

http://en.wikipedia.org/wiki/Ionosphere

Over the years certain knowledge becomes shifted to a part of the brain that is harder to access. It is as if it becomes buried under a stack of information that I try to recall on a more regular basis. Such as knowing that different levels of the ionisphere exist, the lower level D (I mistakenly refered to as possibly being C), sort of allows a window of opprotunity for us Part 15'ers during the daylight hours. That opprotunity is a chance of a clear frequency.  And according to the article, It is probably the F layer (instead of the E layer I referenced above) which allows stations broadcasting with 10KW (and nonexistent to us) during the day, to completely take out our Part 15 AM stations at night (although that same station may operate at greatly reduced power at night).

Thanks for the link Carl 🙂
I needed my memory refreshed.

The last time I really studied (effects of) the ionosphere would have been 30 some years ago... and although I remember the basic, I forget basic things such as which layer is which letter. It is reassuring to know that I still knew which level preformed what measure...although I named both with one letter lower than their actual lettering.

At least I'm not too senile... not yet anyway. 🙂
only enough that I had come back and edit a few times.

[humor]
Us Part 15'ers seem to have our own sphere... The Line-O-sphere.
Now it all boils down to making measurements and duplicating this phenomenon... which could become quite involved.

Is anybody else experiencing the "line-o-sphere" ?
[/humor]

The line-o-sphere sounds like what we have.

Now what'll we do?