Perhaps Mr. Rich would agree that his estimations are based on transmitting sites themselves being in open, clear locations, producing full wave-length radiation leaving the tower. Once it travels to where the buildings are it flows among those buildings as described.
The primary point I think made by Artisan is that the antenna for an AM station does not perform so favorably if it is crowded close to solid obstructions, which prevents ever generating full bodied wave lengths.
The chopped-off out-of-phase AM signals generated at close range to obstructions are not able to recover their coherency as they spread into the surrounding space.
I use the Talking House with external antenna option called ATU.
I have tried it both ways, on the ground with radials and on the roof with and without radials.
The roof mount won hands down. There was no separate ground wire connected for the roof mount. The radials did provide a slight increase in the far field signal. I'm currently using it without radials.
As for compliance, the test data supplied to the FCC for certification states that it used 8 meters of coax (about 28 feet.) It does not specify if the ATU was elevated vertically or just separated horizontally.
One Part15 member using the TH and ATU mounted on the roof was inspected by an FCC Field Agent and had no problem.
So, we can run the Talking House units say indoors in an attic or somewhere, then drill a hole outside for coax to the antenna. Skip the ground and we are complaint?
With your indoor, no ground wire roof mount, what is the type of antenna you have on the roof and realistic listening distance from that?
Can send you a private message if think that is more appropriate.
The Talking House transmitter is in the basement of a story and a half Cape Cod style house.
The ATU is mounted above the TV antenna which is about 6 feet off the roof.
The ATU is a manually adjustable antenna tuner. It has a meter built in to tune for peak output. A standard 102" CB whip antenna screws into the ATU.
The coax is probably about 40 or 50 feet long. I used 75 ohm CATV cable. I'm sure there are much better choices but I had a box that was abandoned by a CATV installer.
There is a system sold by the name INFOSPOT. It is built around the newer version Talking House known as the I AM RADIO system. Pricey due to the options included but well made. Check the ALPB WEBSITE for a link to that. Look in the NOTEWORTHY column, bottom right of the home page.
Both Radio Systems (maker of the I AM RADIO) and ISS (INFOSPOT maker) caution that connecting a separate ground to the ATU may affect compliance depending upon length of the ground wire.
"Check the ALPB WEBSITE for a link to that. Look in the NOTEWORTHY column, bottom right of the home page."
Was just curious...was the domain for .org already taken thus had to revert to a .com domain?
Not that it matters any, but most non-profit organizations use .org or .info as the .com usually is used for profit companies.
.org - organizations
.com - businesses
.info - information
.net - networks
Many others too!
RFB
"to note that the groundwave signals of MW broadcast stations suffer very little additional loss with respect to their theoretical values for given paths without obstructions, even after traveling across a large city full of physical obstructions that completely block the line-of-sight paths from the transmit antenna to receive antennas at those locations."
This is verifiable. I have a 3 meter ground mounted 219 setup used as a backup and maintenance take-over for my CC station. It sits 1 meter off the ground, tied to an 8 foot ground rod with 3 inches above the ground. 4 10 foot long radials laid on the surface, with a metal mobile home less than 8 feet away from it, surrounded by a 4 foot high chain link fence and a couple of trees that dwarf the height of the 3 meter stick, and that signal gets out just fine in the direction of the mobile home, which one would think the mobile home would seriously affect the signal, it doesn't.
RFB