AM Stations Antenna Patterns
 

Does anyone know where I can obtain a plot of the antenna pattern for
a major (50,000 watt) commercial broadcast station?

Ted-

"Ted Jensen" wrote in message
...
Does anyone know where I can obtain a plot of the antenna pattern for
a major (50,000 watt) commercial broadcast station?

www.radiolocator.com (where you'll find it, and any other AM station in the US and
Canada)
--
-----------------------------------------------------------------------------
If there's nothing that offends you in your community, then you know you're not
living in a free society.
Kim Campbell - ex-Prime Minister of Canada - 2004
-----------------------------------------------------------------------------
For direct replies, take out the contents between the hyphens. -Really!-

Ted,

Does anyone know where I can obtain a plot of the antenna pattern for
a major (50,000 watt) commercial broadcast station?

Plenty of them at www.radio-locator.com
--
Philip de Cadenet - London, SW3
Transmitters 'R' Us
http://www.transmittersrus.com

Does anyone know where I can obtain a plot of the antenna pattern for a major
(50,000 watt) commercial broadcast station?


Which one. There are several hundred which are 50 kW.

Perhaps the most interesting Class A pattern is WSAI's.

"Ted Jensen" wrote in message
...
: Does anyone know where I can obtain a plot of the antenna pattern for
: a major (50,000 watt) commercial broadcast station?
:
: Ted-
:

Check here.
http://www.radio-locator.com/

Ted Jensen wrote:
Does anyone know where I can obtain a plot of the antenna pattern for
a major (50,000 watt) commercial broadcast station?

Go to your local station and ask to look in the public inspection file.
There should be one there. If you ask the engineer nicely (and they are
a station that still has an engineer), he might also have some old proofs
so you can see how widely the pattern varies from year to year.

Be aware that the plot for a 50KW station on a stick in Montana will be
radically different than the plot for the same transmitter and tower in
Arizona. Which is what makes it fun.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

"Ted Jensen" wrote in message
...
Does anyone know where I can obtain a plot of the antenna pattern for
a major (50,000 watt) commercial broadcast station?

Do you want antenna pattern or station's coverage?

Pattern is easy. There are a number of on-line sources including the FCC's
AMQUERY. You can also download the whole AM database and display patterns
in my AMSTNS program available (with very recent data) from
http://home.earthlink.net/~lvehorn/

Coverage is hard, since interference from other stations is involved - a
simple field strength prediction is not adequate. The only RELIABLE source
I know for interference-free coverage is to look up the station's actual
application on the FCC's AMQUERY.

73 de bob w3otc

"Ted Jensen" wrote in message
...
Does anyone know where I can obtain a plot of the antenna pattern for
a major (50,000 watt) commercial broadcast station?

www.radio-locator.com

Note that the maps are careful labeled "for entertainment purposes." They
are not totally accurate,a nd very,very, very exaggerated. On AM, the only
useful contour is the innermost circle... and it is actually bigger than
reliable reception areas really are in most cases. The outer two circles are
totally meaningless.

This only assumes you are in the US, one of few places where "major" and
"50,000 watt" are synonymous.

On 3 Oct 2004 00:29:17 GMT, Ted Jensen wrote:

Does anyone know where I can obtain a plot of the antenna pattern for
a major (50,000 watt) commercial broadcast station?

Go to www.fcc.gov. There's an AM database that has the information and
patterns for all stations.

Rich

Does anyone know where I can obtain a plot of the antenna pattern for
a major (50,000 watt) commercial broadcast station?

www.radiolocator.com (where you'll find it, and any other AM station in
the US and
Canada)
____________________

The contours shown on Radiolocator.com are based BOTH on the radiation
pattern of the transmit antenna system, and ground conductivity along
various radials for 360° around the transmit site.

If conductivity was a constant throughout the groundwave coverage area of
the station (almost never happens), then from the "patterns" on
Radiolocator - to the extent they are accurate - you could calculate the
actual shape of the transmit antenna radiation pattern, remembering that
field strength changes as the square root of changes in radiated power.

RF

Visit http://rfry.org for FM broadcast RF system papers.

Rich Wood wrote:
Does anyone know where I can obtain a plot of the antenna pattern for
a major (50,000 watt) commercial broadcast station?

Go to www.fcc.gov. There's an AM database that has the information and
patterns for all stations.

Y'know, that's where I was going to send him, but...

The patterns *aren't* there.

OK, there's a table that shows the relative field every (5? 10?) degrees
of azimuth, and I suppose you could plot it yourself.

For FM and TV stations, they *do* have the DA patterns...

I usually use Bob Carpenter's AMSTNS program.
http://home.earthlink.net/~lvehorn/
--
Doug Smith W9WI
Pleasant View (Nashville), TN EM66
http://www.w9wi.com

www.radiolocator.com

Come on, Bob. You should know better than that. Radio-locator.com's maps are
clearly labeled "This image is intended solely for entertainment purposes," and
quite frankly belong in the funny papers, since they bear no resemblance
whatsoever to either the FCC-approved directional pattern or any sort of
real-world coverage (even though the program's coder claims they're drawn using
FCC data).

R.J. Carpenter's AMSTNS and TVFMSTNS programs are the real McCoy, since they
plot the patterns directly from the FCC data, and they're the only programs I
know of with such information that are updated periodically. Even though
they're DOS programs, they run just fine on the versions of Windows that only
have DOS emulators (i.e., NT, 2000 and XP).

The patterns *aren't* there.


They used to be ... deleted as a "Y2K" cost saving measure.



OK, there's a table that shows the relative field every (5? 10?) degrees of
azimuth, and I suppose you could plot it yourself.


They were every 5 degrees, with both theoretical and "standard pattern" ...
plus "augmented" pattern, if augmented.

Also, the precise bearings of the pattern minima and maxima were provided,
including any local maxima and minima.

"Sid Schweiger" wrote in message
...
www.radiolocator.com

Come on, Bob. You should know better than that. Radio-locator.com's maps are
clearly labeled "This image is intended solely for entertainment purposes," and
quite frankly belong in the funny papers, since they bear no resemblance
whatsoever to either the FCC-approved directional pattern or any sort of
real-world coverage (even though the program's coder claims they're drawn using
FCC data).

R.J. Carpenter's AMSTNS and TVFMSTNS programs are the real McCoy, since they
plot the patterns directly from the FCC data, and they're the only programs I
know of with such information that are updated periodically. Even though
they're DOS programs, they run just fine on the versions of Windows that only
have DOS emulators (i.e., NT, 2000 and XP).

Oh, my! I just made the connection. I've got a copy of Bob's software, discovered
quite by accident somewhere, and it's given me hours of fascination. The only reason
I suggested radio-locator is because it integrates the pattern with a map, and I
honestly didn't think the inquirer had much need for anything more than a
representation.

But, come on, back at'cha...you know the reason why the disclaimer "for entertainment
purposes only" is there is because there's no desire on the part of the website to
become embroiled in some twit's lawsuit when it's used as a source for a frequency
search. At the same time, I don't think that the radiation pattern or inverse-km is
what's being sought, here, but an estimate of what this station's reasonable coverage
area is. In that regard, 2 mV/m or 4 mV/m doesn't really make a whole lot of
difference....especially with the crud that's all over the AM band these days.
--
-----------------------------------------------------------------------------
If there's nothing that offends you in your community, then you know you're not
living in a free society.
Kim Campbell - ex-Prime Minister of Canada - 2004
-----------------------------------------------------------------------------
For direct replies, take out the contents between the hyphens. -Really!-

Thank you for the nice comments about AMSTNS (and TVFMSTNS).

What makes these most useful is that Larry Vehorn, W9AJ, keeps the data up
to date. You should be thanking Larry for all his effort. He's doubtless
very busy as the transmitter guru for over a dozen transmitters ranging from
Class A FM through UHF TV to 500 kW shortwave beasts. And they are spread
from one end of the USA to the other.

73 de bob w3otc

On 4 Oct 2004 06:06:23 GMT, Doug Smith W9WI
wrote:

Y'know, that's where I was going to send him, but...

The patterns *aren't* there.

That's strange. My copy has them.

Rich

"John Rethorst" wrote in message
...
In article ,
pamthis (Sid Schweiger) wrote:

Radio-locator.com's maps are
clearly labeled "This image is intended solely for entertainment
purposes,"

Radio-Locator's Coverage Maps FAQ
(http://www.radio-locator.com/cgi-bin/page?p=maps) says:

"To a large degree, AM radio signals travel through the ground"

which I find pretty entertaining.

Why? Groundwave coverage is the principal means of AM station listening.

"David Eduardo" wrote in message
...

"John Rethorst" wrote in message
...
In article ,
pamthis (Sid Schweiger) wrote:

Radio-locator.com's maps are
clearly labeled "This image is intended solely for entertainment
purposes,"

Radio-Locator's Coverage Maps FAQ
(http://www.radio-locator.com/cgi-bin/page?p=maps) says:

"To a large degree, AM radio signals travel through the ground"

which I find pretty entertaining.

Why? Groundwave coverage is the principal means of AM station listening.

Although (at the risk that I'll trigger another lesson by Mr Fry about antenna
theory) even the term "groundwave" is misleading. Groundwave propagation is due to
the refraction of the wavefront by the earth....this is one of the reasons why lower
frequencies have a longer groundwave pattern, and why, in the extreme low frequency
band, it goes clear around the earth. The effect is also evident at VHF and higher
frequencies, like the 950MHz STL band. Objects presented to the wavefront (like
mountain ridges) which are similar in size to the wavelength will bend the wavefront,
which results in the limited ability to design an STL path which is (slightly) over
the horizon. It's called "razor's edge" propagation then.
--
-----------------------------------------------------------------------------
If there's nothing that offends you in your community, then you know you're not
living in a free society.
Kim Campbell - ex-Prime Minister of Canada - 2004
-----------------------------------------------------------------------------
For direct replies, take out the contents between the hyphens. -Really!-

"Ted Jensen" wrote in message
...
Does anyone know where I can obtain a plot of the antenna pattern for
a major (50,000 watt) commercial broadcast station?

Ted-




Try http://www.fccinfo.com


GST

"John Rethorst" wrote in message
...
In article , "David Eduardo"

wrote:

Why? Groundwave coverage is the principal means of AM station listening.

I had thought that groundwave referred to signals moving through the air
but
following the earth's surface, rather than actually moving through the
ground.

Bob Haberkost explains this well; the main point is that it is not reflected
skywave.