"Richard Fry" wrote in message
...
"Dave Pitzer" wrote
... Is there any place I can find polar graphs of commercial
broadcast station's antenna patterns?

___________________

Dave,

Here http://www.radio-locator.com/ is a link to a website with calculated
coverage areas/contours for US AM broadcast stations. The contours are
based on their licensed radiation patterns (directional or not), AND
ground conductivities for the geographic regions concerned.

The polar radiation patterns of these stations most probably don't look
much like these plots, because of the heavy influence that ground
conductivity has on received field strength along the various azimuth
bearings.

Even the real coverage contours of AM broadcast stations using omni
antennas usually are anything but omni, due to the effects of varying
ground conductivities around their various azimuth sectors and ranges.

Have fun.

Just a FYI...the contour maps at Radio-Locator.com are WRONG....the LOCAL on
FM maps is actually the distant or Service Contour (1mv or 60dbu
level)..LOCAL is defined as City Grade or 70dbu or 3.16mV level...which they
do not show..On AM, they show lower levels on the map as well...If you want
to really know what the signal level should be, draw another circle or line
inside the LOCAL one they show...about the same distance between the LOCAL
and Distant they show...Your line drawn will be local, their local becomes
Distant and their Distant becomes Finge...
Their Fringe is now DX

Chris
WB5ITT

"CWB" wrote:
Just a FYI...the contour maps at Radio-Locator.com are WRONG
....the LOCAL on FM maps is actually the distant or Service Contour
(1mv or 60dbu level)..LOCAL is defined as City Grade or 70dbu or
3.16mV level...which they do not show..On AM, they show lower
levels on the map as well.
_____________

Their maps DO correctly show the distances to the contours for the field
strengths they identify. Radio-Locator picked different field strength
values for the "local" etc contours than those used by the FCC, but that
doesn't invalidate the Radio-Locator maps.

And their choices are reasonable. For example on AM, a 2.5 mV/m signal
(Radio-Locator's local contour) does provide good service to a typical cheap
table radio inside a home in an urban setting.