RE: I’ve never come across a single indication found in any published documentation … or for that matter in any technical calculations that 15.219 achieved greater distances than about a mile.
NEC4.2 shows that a 3m Base-driven Whip+Tx @ 10m AGL, 10m Lead from Tx to Ground Rod, 100 mW d-c input to Final RF Amplifier, 65 mW PA RF Output Powe…[Read more]
Example of “Obstruction Loss” to a MW AM Signal
Q: What loss of field intensity does a single private home cause to the groundwave propagation of a MW AM signal?
A: The signal strengths shown on a Tecsun PL-880 receiver tuned to a 500W AM broadcast station located 55 miles from the receiver location were …
Outside the east wall: 37 dB…[Read more]
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…[Read more]
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…[Read more]
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…
RE: “You’ve not made a response to any of the views expressed in this thread of yous Rich. You asked, we answered. Is your reaction only silence? Or are you still mulling it over?…”
Still mulling it over.
I expect that to take a very long time, as many of the responses made to my opening post continued the practices I was h…[Read more]
RE: … maybe it’s possible that some obstructions have little or no effect on MW signals? Comments?
Comment: Yes, that is a “given”except in the near field of re-radiating obstructions.
If the obstruction is a non-conductor then it has no near field of its own.
Imported from a recent post on Part15.org, comments to which are embedded below:
I’m personally getting rather tired of the discussions surrounding Part15.219 (or RSS210) antennas, ground leads, etc. The intent always appears to be negative in nature, and an attempt to discourage current and future Part 15 broadcasters. …
From co…[Read more]
Actually, my opening post in this thread contains some information I hadn’t previously seen or posted on Part15.org.
I thought it would be of interest here, given the emphasis this site has given to FCC Part 15 issues.
There has been some online comment to the effect that commercially-produced Part 15 AM transmitters with internal loading coils typically cannot impedance-match the transmitter to antenna systems with radiating lengths longer than about 3 meters.
Clarifications/comments about this:
- Typical radiating conductors of Part 15 AM antenna systems…
RE: It is what NEC does with Part 15 level signals, and their application in the real world (not a dream world, full of simplifying assumptions) that is in question. That does NOT include ignoring obstructions, as most of your posted simulations and results do. I note that you do not answer my question as to whether NEC can model obstructions,…[Read more]
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