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For the “think tank” …
Below is a 3D graphic of the field intensity for the conditions described there.
- The elevated, center-fed dipole is shown, with adjacent red lines displaying the current and phase distribution along the two sides of the dipole
- The feedpoint is shown by the red marker at the center of the dipole
- The loading coil is shown by the blue marker just above the feedpoint
Note that at a distance of 1 mile along an unobstructed path, the field intensity vs elevation above the earth shown by the color coding there is rather uniform. However it is highest in the horizontal plane (zero feet elevation).
This differs from the expectations that the greatest radiated field intensity would exist at the radiation center of the antenna system — to enhance the “coverage” of that elevated installation (other things equal).
The key sentence in the last post is “unobstructed path”. I appreciate the difficulties of simulating the effects of obstructions, which is why some real world testing needs to be done, with careful note of obstructions, type (natural or man-made, construction materials for the latter), etc.
The actual hypothesis is that adding obstructions will change that graph significantly (i.e., it doesn’t address the effect of elevation along an obstructed path).
RE: … The actual hypothesis is that adding obstructions will change that graph significantly (i.e., it doesn’t address the effect of elevation along an obstructed path). …
The following two graphics were posted on Part15.org several weeks ago,* and show the measured results when a tall, steel-reinforced building, or natural terrain elevation obstructed the groundwave propagation paths of a medium-wave signal.
Their effects on that MW propagation are not as serious as might be anticipated.
* Thread = Ground-mounted vs. Elevated MW Monopole Antennas: Which Configuration Is Better?
I’ll wait for actual field strength measurements of Part 15 level signals, thank you very much.
Incidentally.. Usually I don’t get much benefit from your charts at all anyway, mostly due to my own limitations of comprehension of it, but think it worth saying, considering the chart below.. Keith Hamilton (in my email correspondence) specifically mentioned it:
‘These formulas are designed for higher power transmitters, not part 15. For example my part 15 has no loading coil. The efficiency is higher then he mentions. So his calculations are not that useful I think”
Like I said, I don’t understand your charts most of the time anyway, but I’m interested to her your response on this.
Edit: oops! Forgot to add your graph in question!
It just occurred to me that I did not request permission from him to post that.. I don’t particularly think he would object.. But I don’t generally consider correspondences confidential unless it’s specified as such. So if anyone says something to me in private that you want to stay private, then tell me!
Nevertheless, I really should have okayed posting the quote before making it public.
‘These formulas are designed for higher power transmitters, not part 15. For example my part 15 has no loading coil. The efficiency is higher then he mentions. So his calculations are not that useful I think”
From End 80: Like I said, I don’t understand your charts most of the time anyway, but I’m interested to her your response on this.
End80: I posted a comprehensive reply to you about this in this thread, but it has “gone missing.”
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