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AM Stations that broadcast from the top of tall buildings

S

stormy01

I know there are not too many AM stations anywhere in the world remaining that do this, since how good of a grounding system as aprt of their tower could a station possibly devise on a tall building's roof vs. the soil?

Would like to know where, what power and frequency. I know that there is just two in the Chicago area: WNTD is on 950 that operates from a site near the downtown CBD aka "Loop" with 1kW daytime ND, and switches to another site for the night hours with 5kW and directional. Then there's WPNA 1490 in Oak Park - the old WOPA, atop what was called the Oak Park Arms Hotel (now a retirement community) The Chicago area had another station atop a building in Chicago on 1240 (WCRW) up to the 90's, I believe.

I would suspect most AM stations atop buildings that remain in operation are now the so-called "graveyarder" frequencies: 1230/40, 1340, 1400/50/90.
 
AM site; WCRW, Chicago broadcast for 50+ years from the 9th floor (penthouse) of the Embassy Hotel on Chicago's gold coast.

Lots of Chicagos fm's have transmitters on Sears or Hancock, and New York's fm's are also on skyscrapers.
 
WGSO, 990 AM, New Orleans. Self-supporting radiator located on the roof of the Radisson Hotel is visible in the lat-lon link (satellite view) under http://radio-locator.com/cgi-bin/info?call=WGSO&service=AM. You can also see it in street view.

Locals say the elevator shaft makes up the other half of a vertical dipole; I do know the bottom of the slant-wire-fed tower structure is heavily bonded to the frame of the elevator structure.

Also visible on top of the building to the right (across Lasalle) is the 100+ ft. pole supporting the antenna for WWOZ-FM.
 
stormy01 said:
I know there are not too many AM stations anywhere in the world remaining that do this, since how good of a grounding system as aprt of their tower could a station possibly devise on a tall building's roof vs. the soil?
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Soil is not an absolute requirement toward providing efficient radiation from a vertical monopole system.

A set of two or more horizontal wires of about 1/4-wavelength each, arranged symmetrically and installed radially around the base a vertical monopole on the top of such buildings produces a very similar radiation efficiency as the same monopole when mounted near the earth, using a conventional r-f ground of 120 buried radials, each about 1/4-wave long.

For more detail see the textbook "RADIO ANTENNA ENGINEERING" by Edmund Laport, pages 139-141.

//
 
stormy01 said:
Would like to know where, what power and frequency. The Chicago area had another station atop a building in Chicago on 1240 (WCRW) up to the 90's, I believe.
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I don't live anywhere near Chicago but I am under the impression that WSBC 1240's tower is on top of a low building and no more than a couple of blocks away, the co-owned AM 820 station (don't know this week's call letters) has its rather tall, self-supporting tower atop another rather low building.

In Los Angeles, two 50-kW stations, KTNQ 1020 and KTLK 1150, have their ground systems on the roof of a massive warehouse that was literally built around the five half-wave towers of what was originally the KTNQ array but later became the diplexed array. The warehouse is cut out for each tower base. Actually, the warehouse is two buildings with a wide driveway between them and a large number of the ground radials of one of the towers run across the tops of both buildings. I've seen a photo taken from the driveway at ground level with the radials overhead crossing the driveway. It's quite a site.

Also in LA, KYPA 1230 just recently moved from its 80+-year-old rooftop L antenna to two of the six towers of the co-owned 1580 AM. In so doing, it became the only US Class C AM that operates DA-1.

Here in Massachusetts, WLLH 1400 licensed to Lowell AND Lawrence (NOT Lowell-Lawrence) is unusual in several respects. It has two synchronous transmitters, one in Lowell and the other in Lawrence. Both used to have rooftop antennas, but a decade or so ago, a new transmitter, using a conventional antenna and conventional ground system was built in Lowell. The Lawrence trasmitter remains atop a building in downtown Lawrence, however.

In Syracuse NY, the Class D AM on 1540 has two sites. Both are within the Syracuse city limits. The day site, which runs 1 kW and uses a conventional tower, is shared with, but not diplexed with, a co-owned 1490 station. The night operation, which runs low power (less than 50W, IIRC), is located on the roof of a building in the downtown area. I had been told that the rooftop antenna was a Valcom whip, but apparently this is not so. The tower is very short, however, and I don't know whether the station had to obtain a waiver of the minimum Class D efficiency in order to use it.
 
DanStrassberg said:
I don't live anywhere near Chicago but I am under the impression that WSBC 1240's tower is on top of a low building and no more than a couple of blocks away, the co-owned AM 820 station (don't know this week's call letters) has its rather tall, self-supporting tower atop another rather low building.
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1240 is a couple of miles to the north of 820, and is a conventional base-insulated tower behind a building. Another of the 1240 sites was indeed a rooftop, but is no longer in use.

Also in LA, KYPA 1230 just recently moved from its 80+-year-old rooftop L antenna to two of the six towers of the co-owned 1580 AM. In so doing, it became the only US Class C AM that operates DA-1.
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Not yet. The DA-1 app is still pending; it's operating under STA as a conventional ND 1 kW.

In Syracuse NY, the Class D AM on 1540 has two sites. Both are within the Syracuse city limits. The day site, which runs 1 kW and uses a conventional tower, is shared with, but not diplexed with, a co-owned 1490 station. The night operation, which runs low power (less than 50W, IIRC), is located on the roof of a building in the downtown area. I had been told that the rooftop antenna was a Valcom whip, but apparently this is not so. The tower is very short, however, and I don't know whether the station had to obtain a waiver of the minimum Class D efficiency in order to use it.
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I'm pretty sure the night antenna is indeed a Valcom.

By day, 1540 is still on its original East Syracuse site, right next to the Thruway. The CP to move to the WOLF 1490 site has not yet been built out.
 
In chicago,, B-96 WBBM and WGCI and the FM WLS 94.7 are atop the sears tower, their power is at class A status, but because they are nearly 2000 feet up, their signals go about 100 miles out... B-96 not as good od signal as other two for some odd reason, they fade about 75 miles out...
 
Mid West Clubber said:
In chicago,, B-96 WBBM and WGCI and the FM WLS 94.7 are atop the sears tower, their power is at class A status, but because they are nearly 2000 feet up, their signals go about 100 miles out... B-96 not as good od signal as other two for some odd reason, they fade about 75 miles out...
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Those are Fms. and every one you mention is a Class B FM... equivalent of 50,000 watts at 500 feet. FMs want to be high up, AM's don't.

The Sears Tower (I'll still call it that) stations are at 1550 feet, and the ones on the Hancock at about 1390 feet. None are at 2000 feet. And the useful range of a B is somewhere in the 40 mile to 50 mile range (the 70 dbu is 32 km out, and most listening occurs in the area inside the 64 dbu contour, which is about another 10 km out.
 
DanStrassberg said:
In Los Angeles, two 50-kW stations, KTNQ 1020 and KTLK 1150, have their ground systems on the roof of a massive warehouse that was literally built around the five half-wave towers of what was originally the KTNQ array but later became the diplexed array. The warehouse is cut out for each tower base. Actually, the warehouse is two buildings with a wide driveway between them and a large number of the ground radials of one of the towers run across the tops of both buildings. I've seen a photo taken from the driveway at ground level with the radials overhead crossing the driveway. It's quite a site.
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There is a little more to it...

The ground system is underground covering the entire piece of property. When the warehouses were built, it was decided that the buildings would potentially reduce the effectiveness of the ground system, so the sytem was duplicated at roof level... covering the parking lot between the buildings, too... across the roofs, and down the far sides of the warehouses and connecting to the radials there with strap. The area over the parking lot, several acres in size, is mesh made of copper wires, which are silver soldered. The mesh also surrounds the tower "cut outs" and to get to the bases, you to to the roof, and then down a ladder to the base. The ATUs are on the roof, though, for ease in servicing them. I have a number of burnt out ATU components decorating my office (along wihth an 892 tube), proof of the fact that 5 500" towers attract lightening!
 
WYSL 1400 1KW Buffalo, NY had their tower on top of the Larkin Warehouse. I don't think it's been there for some time now.
 
No one has yet mentioned WEJL in Scranton, Pennsylvania. This station on 630 gets out VERY well at 2 kilowatts....it also has a very impressive looking tower on a 5 story building in Scranton that they decorate with Christmas lights at Christmas. In the past few years, 910 (the old WGBI) has been diplexed onto the tower as well....

This building/tower is a landmark on the Scranton skyline as it's co-located with the Scranton Times newspaper...an institution in Scranton for probably a hundred years....

Ben
 
I have a question. I work at WGSO, and a former co-worker who formerly worked at WRJW in Picayune, MS as well told me of a time they had to flood the area around WRJW's tower. Since the Radisson building is now condemned and slated for demolition, would it be beneficial for a new tower to be placed near the shore of Lake Pontchartrain to maximize the 1K day, and 400w night signal, and help signal for both sides of the lake?
 
Another rooftop site was located in East Springfield, MA. You may have heard of the calls - WBZ, later to become WBZA when Westinghouse moved the three letter calls to Boston.

This employed two structures with a long wire strung between them - however I'm not sure if they utilized a "ground system" in the traditional sense ... the towers still stand today, dating back to 1921 but are slated for demolition sometime this summer, along with the old factory, to make way for a new strip mall.

http://www.bostonradio.org/stations/wbz-hist.html

http://www.springfieldradio.com/wbza.html

The first link is an article, written by Broadcast Historian Donna Halper, talking about the history of WBZ and the second is a picture of the two towers sitting high atop the Westinghouse building on Page Boulevard in East Springfield.
 
wirelessinnepa said:
No one has yet mentioned WEJL in Scranton, Pennsylvania. This station on 630 gets out VERY well at 2 kilowatts....it also has a very impressive looking tower on a 5 story building in Scranton that they decorate with Christmas lights at Christmas. In the past few years, 910 (the old WGBI) has been diplexed onto the tower as well....

This building/tower is a landmark on the Scranton skyline as it's co-located with the Scranton Times newspaper...an institution in Scranton for probably a hundred years....
Click to expand...

There's a remote-controllable webcam atop this building, and you can see the WEJL tower (with Christmas lights still attached) if you pan about 10 degrees right from the full left position. Just hit the Start Control button, and when you see the green indicator come on, it will give you control for 35 seconds. At full left, the STL antennas for WEZX and sister stations are also visible:

http://www.scrantonlive.com/wc_large.html

As I post this, smoke appears to be rising from the roof of an apartment building, so activity on the camera is high.
 
WSB-AM had an impressive site atop the Biltmore Hote lhttp://cgi.ebay.com/Postcard-Atlanta-Biltmore-Hotel-Georgia-Radio-Tower-WSB_W0QQitemZ260396611254QQcmdZViewItemQQimsxZ20090420?IMSfp=TL090420154005r27952


Also another note, the 97.9 fm frequency(WRFD-FM now WNCI) in Columbus Ohio was licensed for 320,000 watts, altho they never signed on with that power.
 
DanStrassberg said:
the co-owned AM 820 station (don't know this week's call letters) has its rather tall, self-supporting tower atop another rather low building.
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Looked at the aerial photos for WCPT 820 and I agree it seems that the 500' tower is atop a 2-story building. Does anyone know if the tower was built first, and then the building was built around it? Structurally, that seems kind of crazy to expect even a portion of a 2-story building to support the weight of a 500' radio tower!

BTW - That's a nice webcam Scranton, PA!!!
 
Not sure about the answer to your question, but I believe thatthat building/tower have been there since the WAAF days, when the station was a daytimer.
 
Prais said:
Not sure about the answer to your question, but I believe thatthat building/tower have been there since the WAAF days, when the station was a daytimer.
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What was WAAF (AM) is today's WNTD (950), I believe. Today's WCPT (820) has had several call signs in its history, including, IIRC, WSCR. But the call sign that is probably most often associated with the 820 station is WAIT. If I'm not mistaken the WAIT calls are currently on 850 in Crystal Lake. Though long a limited-time station, WAIT was once also a share-timer. The other station in the time-share was WCBD, which was licensed to Zion IL, I believe.
 
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