Re: [IRCA] KXMG-1150-Portland pattern

[Scott Fybush <scott@xxxxxxxxxx>]

Patrick Martin wrote:
> Powell,
> 
> The FCC site with slow dial up is a pain to do. Radio Locator is much
> easier for me to use. But aren't patterns part of what this list is
> about? The last time I checked, it was about radio. :)

It is - and on that note, there's a VERY important difference to note 
between the COVERAGE maps that radio-locator generates and the PATTERN 
plots that show up at the FCC site (or at the most very excellent 
fccinfo.com, which should work nice and fast on dialup for Patrick and 
friends!)

The PATTERN plots that you get from fcc.gov or fccinfo.com - or from the 
NRC pattern book, for that matter - show you what the station is 
actually sending out. The COVERAGE maps that radio-locator generates 
show you what happens to that signal as it travels along the ground, 
where conductivity varies dramatically.

A few good examples to compare might include WENJ-1450 in Atlantic City. 
It's non-directional, and a pattern plot for the station would therefore 
be a perfect circle. But a coverage map for the station isn't even 
remotely circular - it shows that the signal spreads well up and down 
the conductive coastline, very little inland (where it's sandy and not 
conductive at all), and then screams like a banshee over the water. 
(Indeed, the radio-locator map for WENJ isn't zoomed out nearly far 
enough, so you don't see how the signal comes back on land in places 
like the south shore of Long Island and down along the Delmarva peninsula!)

Another good example is the daytime CP for WNSH-1570 in Beverly, MA. 
 From the coverage map on radio-locator, you'd think the signal is all 
aimed east, out to sea. You have to go to an actual pattern plot to see 
that it's not directional at all - it's just the dramatic difference in 
conductivity between the rocky Cape Ann coast and the salt water of 
Massachusetts Bay that creates the coverage variations.

This difference matters, from a DX perspective, because we're usually 
dealing with skywave, not groundwave, and because the skywave isn't 
influenced as much (if at all) by surrounding ground conductivity.

None of this is to say that radio-locator doesn't have its uses. It 
does, and for certain things it's very good, indeed - you've just got to 
know when it is, and isn't, the right tool in the arsenal!

s
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