AM reception is not blocked by buildings or other obstructions except that underneath and inside of structures AM reception often disappears entirely.
And AM transmitting towers are never set up against buildings or other obstructions, and are always located in clear fields or on high rises that have a clear horizon.
In discussions here at part15.us we are talking about transmitting sites.
AM reception is not blocked by buildings or other obstructions except that underneath and inside of structures AM reception often disappears entirely.
Reception of AM broadcast radio waves underneath a building (below the surface of the earth) always is relatively poor.
But such reception inside a typical home in a typical urban environment is not much affected.
If it was, AM broadcast stations would not have the listener base that they do (or once had).
Skipped over my mention that AM transmitting towers are never located near obstructions, so what is the point of what you said?
What branch of the military are you with?
How many db or S units difference is there do you think from inside to outside the house?
For that amount of difference, would it have a more noticeable effect on a Part 15 received signal compared to the commercial station you are receiving?
You know, dropping a 5 to 50 kw signal a couple db compared to dropping an 80 mw signal the same amount.
Skipped over my mention that AM transmitting towers are never located near obstructions, so what is the point of what you said?
You and others should be interested in the clip linked below showing an AM broadcast station tower located within about 50 feet of its studio/transmitter building (extreme lower right of the clip), and also not a huge amount further from houses toward the left side of the clip.
This station has a coverage area that is almost perfectly circular. I know that, because I was the Chief Engineer of that station in the early 1960s.
What branch of the military are you with?
Thanks for asking, but while I served in the electronics field in the U.S. Air Force from 1958 to 1962, my present military status is that of a veteran.
The tower in the picture appears to stand well above a very low profile building with much open space all around.
That is entirely different than a 3-meter stick standing near a wall or other obstruction.
Wow! Would they allow that type of setup today with all the work place EMI, RF exposure limits they have?
I suppose it depends somewhat on the output power. At BCB frequencies it would be less of a problem.
Wow! Would they allow that type of setup today with all the work place EMI, RF exposure limits they have?
I suppose it depends somewhat on the output power. At BCB frequencies it would be less of a problem.
For that amount of difference, would it have a more noticeable effect on a Part 15 received signal compared to the commercial station you are receiving?
It wouldn't (sorry). This is a linear process, regardless of the radiated power, and its field intensity at a given location in the far field.
But seriously, comparing a commercial blow torch signal to a Part 15 match stick, wouldn't the difference between inside and outside be a bit more noticeable.
A couple S units or db could well render the Part 15 signal gone considering the ambient noise in a house.
All I can say is, from experience and not theory, is that in the directions of urban clutter (i.e. obstructions), my transmitter range is relatively poor. In the directions that are relatively open and free from obstructions, it is good (i.e., on the order of 1/4 to 1/2 mile vs 1+ miles). In the one direction, north, there is continuous residential housing. In the other directions, south and west, there is a bit of housing and then open fields. I get the best range, line of sight with the open fields (farmland).
And those directions were consistent with the transmitter setup at two sites here in Pitt Meadows (I first rented a house, and then purchased one).
A couple S units or db could well render the Part 15 signal gone considering the ambient noise in a house.
True about the likely affect of local r-f noise inside a home on the useful reception of AM signals having very low field intensities.
But that local noise does not reduce the field strength of Part 15 signals, only the relative r-f noise voltage to which they are subjected.
Local, licensed AM broadcast stations produce much greater fields than Part 15 AM stations near and in such homes, and so are less affected by such local r-f noise.
That says it all.
In Dade City, FL the local radio station runs 1KW during daylight hours. The tower is located 25 feet behind the studio. The only issue experienced was RF getting into the newer solid state devices.
http://transition.fcc.gov/fcc-bin/amq?list=0&facid=12294
In Dade City, FL the local radio station runs 1KW during daylight hours. The tower is located 25 feet behind the studio. The only issue experienced was RF getting into the newer solid state devices.
http://transition.fcc.gov/fcc-bin/amq?list=0&facid=12294