The KCBS-FM Transmitter Tower

[Gregg]

I noticed that nearly all the Los Angeles FM stations are between 2800 and 3100 feet above average terrain. I assume they're all on Mount Wilson, and some are just a bit higher up the structure. (They can't all be at the very top.)

But the listing for KCBS-FM height above average terrain is 3520 feet, several hundred feet above the other stations. Is KCBS-FM on some other peak? Is that a misprint? (I got it from www.radio-locator.com)

And there are several FM station in the LA market that for one reason or another never got on Mount Wilson and are stuck at lower heights:

106.7 KROQ...6 kw at 1390 feet (And they're owned by CBS... but never upgraded?)
98.7 KYSR...75 kw at 1180 feet (And they're owned by Clear Channel... but never upgraded?)
97.9 KLAX...33 kw at 600 feet (They can't find a taller tower?)

I believe KPWR is the most recent addition to Mount Wilson. KPWR used to be on a 700 foot tower but now they're 3130 feet above average terrain, along with the big boys.


Gregg
[email protected]

 

[K6JHU]

My recollection is that CBS TV built a higher tower, further back on the mountain. If you look, you will see one higher twoer than all the rest. And remember, there is not one tower but several up there.

I plotted all the locations on Mt. Wilson once for a friend who was interested. But I have not updated the chart in years.

Scott, or somebody a lot more knowlegable than me, can give you the exact details.

 

[badjef]

FYI:
The HAAT can differ drastically from one location to another.
IIRC: HAAT is computed by the 8 compass points in a circular direction and then the average is taken.

If 1 compass point is significantly different from the other 7, it will affect the average number.

Mountains can and will affect that number.

Looking at the antenna in person, you won't see that much difference from the ground.

Does it affect coverage? Yes, if there is a mountain (range) higher than antenna.

A station's antenna in a valley can be on top of a 500' building and register as a negative number leading someone to think the antenna is underground.

Jeff in Sa-ra-so-ta!

 

[Lopaka]

Just out of curiosity, why isn't all FM on Mt. Wilson? And why not at the peak, which is about 5000 ft. as I recall? Obviously you could not stick the mutually interfering freqs up there, but for ones that wouldn't interfere, why not take the same advantage that TV always has?

 

[badjef]

Just out of curiosity, why isn't all FM on Mt. Wilson? And why not at the peak, which is about 5000 ft. as I recall? Obviously you could not stick the mutually interfering freqs up there, but for ones that wouldn't interfere, why not take the same advantage that TV always has?

The answer differs with each circumstance.
The short answer is cost. The rent may be more than some broadcasters are willing to pay, especially if they would be paying it to the competitor. The competitor, today, may be co-owned tomorrow. But the reverse can apply, too. (you know, finicky FCC rules change)

For the long answer, in the case of NYC, the necesary height could only be achieved by Empire. Even with Empire, they are running into OSHA problems because of the observation deck.

Tower 1 at old 1WTC had UHF's running at reduced power because of radiation concerns at the upper floors of the South tower (2WTC, Tower 2).

Wind and weather are also concerns.

Interference to adjacent stations or harmonics to other services.

Jeff in Sa-ra-so-ta!

 

[davideduardo]

I noticed that nearly all the Los Angeles FM stations are between 2800 and 3100 feet above average terrain. I assume they're all on Mount Wilson, and some are just a bit higher up the structure. (They can't all be at the very top.)

I'm hoping Scott Fybush will jump in here with his superior knowledge.

But, for the moment, here's what a visitor to the mountain and breifly tenured Chief Opeator of KLVE can contribute.

Mt Wilson is a really a ridge which is fortunate enough to be overlooking the LA basin and the San Gabriel and San Fernando Valley areas of LA. The ridge is part of the Angeles National Park, which is a vast collection of mountains and ridges and peaks and valleys "behind" the LA populated areas.

The ridge is populated with dozens of poles, towers and structures that bear antennas for FM, TV, DTV and many emergency services. Because being right at the edge of the ridge is important to avoid shadowing, support structures tend to be in the 100 to 300 foot range for the most part, which is enough to clear the rim and to not be too close to the ground for OSHA requirements .

But the listing for KCBS-FM height above average terrain is 3520 feet, several hundred feet above the other stations. Is KCBS-FM on some other peak? Is that a misprint? (I got it from www.radio-locator.com)

CBS-FM is on the KCBS digital TV tower, originally Ch. 2. The are set well back from the ridge on a side road to a mountaintop meadow area. The tower itself is about 1000 feet high. Apparently the engineers for CBS thought that the coverage of Ch 2 would be better if it was clearer of the Wilson ridge and could shoot down into shadows of the Santa Monica Mountains, the Baldwin Hills area, and Signal Hill.

And there are several FM station in the LA market that for one reason or another never got on Mount Wilson and are stuck at lower heights:

Before FM was really viable, some stations did not move to the mountain. So cochannel or adjacents were licensed that later impeded the moves of those stations. A few moved late. KSCA was in the 78 kw range on Flint Peak near Glendale, but is 4.8 kw on the mountain. Others had to directionalize to make it.

The early ones, like KHJ FM and Saul Levine's 105.1 were up there around 1960 with high power and were grandfathered in.

106.7 KROQ...6 kw at 1390 feet (And they're owned by CBS... but never upgraded?)
98.7 KYSR...75 kw at 1180 feet (And they're owned by Clear Channel... but never upgraded?)
97.9 KLAX...33 kw at 600 feet (They can't find a taller tower?)

Of the three, KLAX is at Flint, which is a great location. The terrain averaging puts it at a low average, but it is about 1600 feet above the LA basin, and a magnificent site.

The others are at comparable heights and are stations that never could upgrade due to technical issues; the previous owners did not get them to wilson on time, or actually believed the current sites were good and did not need upgrading.

I believe KPWR is the most recent addition to Mount Wilson. KPWR used to be on a 700 foot tower but now they're 3130 feet above average terrain, along with the big boys.

Power and KSCA were on Flint Peak, a magnificent location that some say allows greater power, although at lower height, and good coverage of the LA maket except for the High Desert (nobody covers it well... KISS has another licensed station there to fill in as a network) and Santa Clarita, where boosters are used by many, including the Wilson stations. KLAX is still on Flint, as well as auxiliary sites for Emmis and Univision.

 

[davideduardo]

The short answer is cost. The rent may be more than some broadcasters are willing to pay, especially if they would be paying it to the competitor. The competitor, today, may be co-owned tomorrow. But the reverse can apply, too. (you know, finicky FCC rules change)

The sites are all Forrest Service leases. A few FM stations sublet, but then mostly from TV stations with larger self supporting structures. The issue for the stations not on Wilson that perhaps could have been had they moved in the early 60's is that of adjacent and co-channel protections. They can't move. In fact, except for the two SBS B's the remaining two lower B's have other cluster stations on the ridge.

Again, Wilson is not really a peak but a ridge, with a road along it, and dozens of structures holding antennas along it. And flowing off Wilson is what is technically called Mt Harvard, but is very nearly a continuation of the same ridge-like formation and home to even more transmitters.

Scott Fybush's annotated pics of the ridge are at

http://www.fybush.com/sites/2005/site-051216.html

http://www.fybush.com/sites/2005/site-051223.html

These show how many towers are up on the ridge.

 

[badjef]

With the antennas being on the "ridges" as David describes, they are not the highest peaks so when doing the field work for the computations of height, the antenna of KBIG shows up as 34metres or 111feet. But that is AGL (average ground level) and the HAAT (height above average terrain) as 885meters or 2,903feet and 1,772meters or 5,813 above sea level! That puts it higher than Denver's Mile High Stadium! These are all different numbers to indicate where the antenna is vertically for coverage and protection.

I asked David in another thread, why KBIG powered down. He said OSHA. (I was afraid he would say that.) It was easier to tweak a few buttons than elevate the antenna higher for the radiation protocals. Plus by the time those new protocals were in effect, KBIG probably couldn't go higher with the antenna (although there are probably others around it they could explore multiplexing) and keep the grandfathered power. I believe there will continue to be the radiation issues with FM stations around the country. We saw it here, in Tampa.

Since one direction the ground may be higher, than the others, it is important to make sure that is not in the way of your target market. If it is close enough and on the "backside" of the intended coverage, it might intrinsically aid in manipulating the signal toward the direction of that market.

If memory serves me correctly, if it is a 10 bay vertically mounted antenna, the measurement in taken from the center of the array. If that has changed, please correct me.

Jeff in Sa-ra-so-ta!

 

[Ryan Williams]

Of the three, KLAX is at Flint, which is a great location. The terrain averaging puts it at a low average, but it is about 1600 feet above the LA basin, and a magnificent site.

In your opinion, Flint is an order of magnitude better than Verdugo or the Mulholland site?

 

[davideduardo]

Of the three, KLAX is at Flint, which is a great location. The terrain averaging puts it at a low average, but it is about 1600 feet above the LA basin, and a magnificent site.

In your opinion, Flint is an order of magnitude better than Verdugo or the Mulholland site?

Mulholland is a bit lower, and while Flint gets decent penetration of the northern part of OC, KROQ at Verdugo somewhat to more to the north, does not.

Flint, watt for watt, is best. KLAX, with much less power, covers the morepopulation with its 64 dbu as KYSR with more power. KLAX puts a 64 dbu over 14 million, KYSR over 12 million and KROQ covers 10 million.

 

[davideduardo]

With the antennas being on the "ridges" as David describes, they are not the highest peaks so when doing the field work for the computations of height, the antenna of KBIG shows up as 34metres or 111feet.

Wilson's peak is the entire ridge, with minor differences along the length of the part used for broadcast sites. What lowers the HAAT is the fact that the entire range behind the site is at comparable elevations. So the site is 5200 to 5300 feet above the LA basin below, but only a few feet above the average terrain behind them... thus the average of around 2900 feet above average.

I asked David in another thread, why KBIG powered down. He said OSHA. (I was afraid he would say that.) It was easier to tweak a few buttons than elevate the antenna higher for the radiation protocals. Plus by the time those new protocals were in effect, KBIG probably couldn't go higher with the antenna (although there are probably others around it they could explore multiplexing) and keep the grandfathered power.

There is some restriction on height based on the congestion of facilities there, plus the limitations of newer protection requirements. The station puts a 70 dbu over all the market except a tiny wedge of southern OC, so the power reduction was probably not a concern...

If memory serves me correctly, if it is a 10 bay vertically mounted antenna, the measurement in taken from the center of the array. If that has changed, please correct me.

I think the only ones dumb enough to put a 10 bay on Wilson were the folks from KPFK, which for decades had a 100 kw signal that sounded like a 10 kw one.

 

[IndigoCoyote]

You guys have a pretty nice place to put your FMs down there, but you don't quite have a location like these guys. http://www.montanassuperstation.com/photos.html

Very easily the most powerful 5kW signal you will ever hear. 11,000+ feet above sea level. HUGE contour...which...umm...has fewer total residents in it than Pasadena. A lot fewer. A LOT fewer

Nice signal, though. ;D

 

[MarioMania]

Is there a reason why L.A FM's don't go though the Grapevine??

 

[davideduardo]

Is there a reason why L.A FM's don't go though the Grapevine??

Horizon blockage. FM signals are line of sight. Think of a light bulb... if you hold up something in front of it, the light gets blocked.

FM is similar... mountains, hills, buildings block signals. Like the bulb, a little light may reflect off other surfaces, but in general if the transmitter does not have a clear shot to you, the signal will be minimal or non-existent.

 

[davideduardo]

Very easily the most powerful 5kW signal you will ever hear. 11,000+ feet above sea level. HUGE contour...which...umm...has fewer total residents in it than Pasadena. A lot fewer. A LOT fewer

Got you beat... I put an FM at 14,000 feet... on the side of a high peak in the Andes. And it talked to well over a million people.

 

[IndigoCoyote]

Very cool, David. Any pictures or literature on this project?

 

[wdb2003]

Very easily the most powerful 5kW signal you will ever hear. 11,000+ feet above sea level. HUGE contour...which...umm...has fewer total residents in it than Pasadena. A lot fewer. A LOT fewer

Got you beat... I put an FM at 14,000 feet... on the side of a high peak in the Andes. And it talked to well over a million people.

Yeah radio reception here in Pasadena is not all that great. All the Mt. Wilson stations come in fine off foothill just not the ones in the SouthBay area are all static. I was thinking of visiting Mt. Wilson later this summer before the weather gets ugly again. With Angel Crest Highway reopen again is it safe to drive up there and is there another route to get there?

 

[davideduardo]

Very cool, David. Any pictures or literature on this project?

There's not any pictures of the site, although I have one picture taken from the site looking down on the city... it's at

http://www.davidgleason.com/1964-1970-Building-a-station-group-in-Ecuador.htm

and it's about two-thirds of the way down the page.

 

[robnokshus06]

With Angel Crest Highway reopen again is it safe to drive up there and is there another route to get there?

ACH is open and is the best way to reach Mt. Wilson. The Cosmic Cafe at Mt Wilson is also open, so you can take a nice drive and enjoy lunch when you get there (proceeds go to the observatory).

There is more to Mt. Wilson than just a tower farm. Take some time to stroll around the observatory grounds. One of the most accurate measurements of the speed of light in the early 20th century was taken there. Mt. Wilson is also where Hubble came up with the "Big Bang Theory." There's a museum and docent led tours on the weekends.

Mt. Wilson is also a great hiking destination from various trailheads below. It's a beautiful area with a lot of history. You can also visit it from your desk here: http://obs.astro.ucla.edu/towercam.htm

 

[Gregg]

I thought Chuck Lorre came up with the "Big Bang Theory" not long after he created "Two and A Half Men." Sorry, couldn't resist.

I didn't know the Mt. Wilson Observatory is open to the public. And I wasn't aware that Hubble worked there. I'll have to check it out next time I'm in So. Cal.