The point I am making is that in most if not all of these cases the radiating ground lead is in close proximity to some sort of obstruction. That being said, maybe it’s possible that some obstructions have little or no effect on MW signals?
That, it seems to me, is due to the increased field strength those excessively extended antenna systems were producing making it capable of overcoming those obstructions which the lesser field strength produced by a legal 3 meter system can not.
That's been my experience - without a doubt, buildings certainly do block the signal.. However, I should point out that for at least 4 or 5 years my Rangemaster has been elevated about 12 to 15 feet with nothing connected to the ground lead. If it was grounded properly and legally situated, perhaps my experience would be different.
But the conclusion is the same: higher field strengths can penetrate obstructions which weaker field strengths cannot.
Which brings up another thing.. The talking house is certified to operate by achieving ground via the neutral plug on the power receptacle.. therefore legal. So, if I put a power outlet on my roof and grounded my Rangemaster in the exact same manner, would it be considered legal?
Maybe, maybe not. Depends on the FCC inspector. But you could certainly plug in a Talking House or Talking Sign ( that has been certified for use in that manner). I mounted my Talking Sign on the ceiling and ran the wire antenna outdoors above the roofline, which essentially achieves the same thing. No extension cord, just the stock transmitter.
Maybe, maybe not. Depends on the FCC inspector. But you could certainly plug in a Talking House or Talking Sign ( that has been certified for use in that manner). I mounted my Talking Sign on the ceiling and ran the wire antenna outdoors above the roofline, which essentially achieves the same thing. No extension cord, just the stock transmitter.
Well there was a gentleman who had a rangemaster any put it inside of a church steeple and he was able to get out to miles and I don't think there was a ground.
The trick would be to take a talking sign or talking house or iAM transmitter inside that same church steeple and see what type of range increase or decrease there would be. It could be a good work around.
RE: But the conclusion is the same: higher field strengths can penetrate obstructions which weaker field strengths cannot.
What do you think about this explanation?
- For a given set of propagation conditions, obstruction loss in percent of transmission and/or decibels of loss is the same for all e-m field intensities, regardless of the arriving field strength of that e-m wave.
- Obstruction loss may reduce a "weak" signal to a level that is unusable to a receiver, but
- That same obstruction loss to a "strong" signal may still leave enough of it for useful service to that receiver (other things equal)..
But you’ve gone on record stating that you measured no field strength loss of a licensed radio signal due to an obstruction.
My last post didn't say or imply that all obstructions have loss, just described how any loss that might exist in an obstruction would affect a weak or strong e-m wave while it was passing through that obstruction.
Even though a signal may be weak within an obstruction such as a building, the field usually recovers to the same strength beyond the building that it had on that same radial before it crossed the building.
In fact, a MW broadcast signal can travel through a whole city-full of structures, and have a field intensity beyond all those structures as strong as if those structures didn't exist.
The story keeps changing.
All I know is that your last statement certainly doesn't hold in the real world for Part 15 MW broadcast signals.
Yeah well, I agree, in this thread you seem to be saying obstructions do disrupt or block a signal, but that it will recover again some distance beyond that structure, and its strength at that distance will be equal to if there was no obstruction anywhere in that path at all..
I guess I can agree with that in the real world of part 15, however in most cases, like for example a subdivision or a city block that first obstruction is going to be followed shortly by another structure, and beyond that another.. etc, leaving no room for that signal to recover before there's nothing left of it.
You also seem to be saying an obstruction affects a weak signal to the extant of it being unusable, and that same obstruction affects a strong signal to the same extant but there's enough of it left over to be useful..
Which is basically the same thing I just said.
Yet in other threads (as Artisan pointed out) you insist an obstruction has no effect on AM regardless if the signal is weak or strong.. which sounds ridiculous to me.
But underlying all this, your main point seems to be that obstructions do not effect field strength at all.. which may be true in itself.. but that doesn't mean obstructions don't affect reception. It obviously does. And if the reception is blocked then it's unusable. -And that's the whole point.
Obstructions block the weak signals of part 15 AM, but with a long ground lead that signal increases and can overcome an obstruction.
This is all interesting to me. The way I see it as described about medium wave broadcasting and obstructions is that the wave only follows the radials which from my understanding about Radio waves is that they are like thousands of imaginary lines in space. So if a structure blocks some of those waves which are like thousands of very tiny imaginary lines than how can you say that some of those lines of waves recover?
And since I'm at it would a weaker signal like a 100 milliwatt signal be effected more harshly by an obstruction than say a 50 killowatt station? This could explain why I'm having so much trouble getting my signal towards the Deltaville market. My signal seems to drop along the horse shoe road I travel on towards 7-Eleven. Then there is a point right there where the signal gets very weak but after I cross the highway and travel towards the market by the time I get to Sunset Grill it gets a little stronger and follows that side of the street to the market with that weaker signal.
If the trees were not there would I have that same beefier signal I had just before the big drop at 7-Eleven?
As I travel on the other side of the horse shoe the signal does seem like it cuts right out after I pass the complex but then comes back somewhere in the middle of the horse shoe road. Its a little stronger and when you get near the bay it seems to magnify. The trees do seem to cut the signal drastically around the bay area as I pass underneath them. When I reach the end of the horse shoe road it picks up a bit and you have a better signal all the way to Taylor's restaurant.
I'd really like to know what carrier current would do if there isn't a way to get portable Radio range to be a bit better so folks can listen as well as in a car. I'm still thinking the antenna will have to be higher. We'll try some other antenna designs and see what happens. This is an ever changing experimental thing.
Below is a graphic showing how that condition can be true.
Examine the region between 50 and 100 meters from the transmit antenna of a "Part 15" AM station (distance is plotted along the horizontal scale of the graph).
The total field intensity along the horizontal plane is shown by the topmost line plotted on the graph, and references the vertical scale (E).
No obstructions were included in the NEC model producing this graph.
The field at a height of 1.5 meters above (level) Earth is:
- ~ 2.9 mV/m at a horizontal distance of 50 meters, and
- ~ 1.4 mV/m at a horizontal distance of 100 meters
The field for an added h-distance of 50 meters has been reduced by a factor of about 0.5X.
IF for a given Part 15 AM station there was a building located between 50 and 100 meters which blocked that propagation path, a Part 15 operator might conclude that the building was the reason that the field from his station was 50% lower beyond the building than in front of it, with respect to his transmit antenna, even if the building had no affect on that signal. However this conclusion would be incorrect.
That reduction was due to the difference in path lengths, not due to the building.
As a contrast, the signals from licensed broadcast stations would arrive over much longer propagation paths, where their field strength changes relatively little for a distance change of 50 meters.
This reality might lead to a conclusion that "obstructions" affect the radiated fields of Part 15 AM stations differently than licensed AM broadcast stations — when for the same set of conditions, in fact they don't.
Try Again
Rich: "...but with a long ground lead that signal increases and can overcome an obstruction."
That is a generalization and an assumption and probably also an exaggeration.
Please identify which Rich you are quoting (not me, in this case).
Looks Like It
Rich notes: "Please identify which Rich you are quoting (not me, in this case)."
I guess so.
Too bad because I made a strong point had it been you.
What can be done about the past?