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Online Website That Shows Transmission Pattern Maps

S

spinjector

A while back I stumbled across a website that shows transmission patterns overlaid on top of a map of the surrounding area.

I've been trying to find it again, but I can't remember what/where it is. I thought maybe it was FCC.gov, but all they seem to have is pdf files with plots of the theoretical mathematical pattern - and not on a map.

Does anyone happen to know what site it was?

Thanks.
 
You know, I was wondering - where do we get coverage maps?

The only place I've ever seen them is www.radio-locator.com.

But where do they get their data from?

I've been all over the FCC website, and I've only been able to find those theoretical mathematical plots in radial graph form in PDF.
 
Go to the FCC Media Bureau site (http://www.fcc.gov/mb), select FM query from the "shortcuts" menu, identify your station, and among the data returned will be a link for the coverage contour which is overlayed on a Tiger census map. Keep in mind that official FCC contour maps do not necessarily reflect real-world coverage.
 
What about AM..? We've got four AM here; no FM...

That link you gave me is the pages I've been looking at, but I've not been able to find any topographical coverage maps for any AM stations.
 
Getting the underlying "official" coverage maps for AMs, unless they're relatively recently-built, is difficult without going through the actual FCC files, most of which were not converted for on-line review. The place you will find them is in the technical exhibit portion of the original application, supplied by the applicant rather than produced by the Commission.

For those that are available on-line, here's how to find them: Do an "AM Query" from the shortcuts menu of the FCC Media Bureau site (fcc.gov/mb), and on the results page scroll down to the "Applications List" link, which will take you to the list of all applications for that facility. For each you will find an "Info" link and an "Application" link, the latter of which (if not "grayed out") will take you to the original application, which should contain the coverage map in the form of an exhibit attachment. Look for the construction permit application form 301.

Further, clarifying, AM coverage maps are not based on topography (unlike FM), but rather on RMS field and ground conductivity.
 
maineengineer said:
Further, clarifying, AM coverage maps are not based on topography (unlike FM), but rather on RMS field and ground conductivity.
Click to expand...
I was wondering that, with FM being line-of-sight, and AM being ground wave & sky wave.

Wouldn't one have to go out in the field to get the measurements?

And regarding FM, how do they do it?

I guess I should ask how is either one done at all? Aren't they all done out in the field? Or are some just math estimated against topography maps, or what exactly?
 
From an FCC standpoint, it's now all computer-predicted at the application stage, for both AM & FM, based on tower heights, power levels, and ground conductivity maps for AM and topographic data bases for FM. Directional antennas are another matter, with field measurements typically required to confirm the patterns at the licensing stage.

Still, the way the FCC predicts coverage can be wildly different from the real-world coverage achieved, due to averaging and environmentally-influencing factors, which applicants often use to their advantage to serve areas far beyond their allocations. Ironically, licensees can only promote their reach based on their "official" FCC map. Particularly for FM, those maps are certainly "precise" but definitely not "accurate."
 
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