Los Angeles radio tower crash kills 2

It will be interesting to see if they have to go through the application
process to put up a new tower at the same location.
It will be even more interesting to see if they apply for a taller tower.

G.R. Patterson III wrote:
Seems to me that this is an ideal opportunity for the station to add those
lights, since they have to put up a new tower anyway.

IIRC, I don't think they have to submit a new application in order to
replace an existing tower.

And a radio station can't just put up a tower anywhere they can find some
empty real estate. Again, an engineering study is required in order to
locate/relocate a tower.

A couple of points: for FM and TV broadcasting, you have an antenna, called
a radiator, which actually "broadcasts" the signal. This antenna is then
ATTACHED to something, normally a tower, either ground-based or on top of a
tall building or other structure. But, in this instance, the tower is only
used to hold the antenna up to a desired height; the tower itself is not
part of the antenna. Consequently, the length (or height) of the tower is
immaterial from the standpoint of radiating the signal, other than the fact
that taller is generally better.

But KFI is an AM station, which is another whole ball of wax. In AM
broadcasting, the tower itself is the antenna, it is the part that actually
"broadcasts" the signal. For this reason, the tower must be of a specific
height, based on the frequency on which the station broadcasts. This is
based on the length of one "wave", normally a sine wave, of the carrier
frequency. I've forgotten the exact formula, but it has to do with the
frequency and the speed of light, which will give you the length of that
wave.

Most of towers I have seen are what are known as "quarter wave" towers,
although I have heard of a couple of half wave towers. This means, that the
actual height of the tower is equal to one quarter of the length of a sine
wave of the station's frequency. KFI's frequency is 640, which means each
wave is longer than the wave of a station broadcasting at 1590; hence the
tower must be taller.

Also, AM stations require a ground system, which is not required for FM or
TV stations. The ground system consists of a series of wires, buried
underground, each the length of the tower, and located at 10 degree (IIRC)
radials emanating from the tower base. Imagine the radials extending out
from a VOR every 1 degree, although these are not actual, physical, wire
radials. But for AM radio, these are actual wire radial, extending out every
10 degrees from the tower, with each radial the same length as the tower.
And you can't build anything on top of these radials, other than a small
transmitter building, as it will disrupt the signal. Which is why there is
always a large open area around AM towers that is not necessary, from a
broadcasting standpoint, for an FM or TV tower.

One other note, I have heard of some towers that provide a "lower" section
of the proper length which serves as the AM radiator, then have an
electrically isolated upper section which is used to support FM, TV, or
other antennas.

And broadcast antennas, AM/FM/TV, must be located such that they don't
provide any interference to other broadcast stations.

So, relocating a tower, in a densely populated area such as LA, with a large
number of broadcast stations, would be a very tricky job, that would require
a lot of engineering studies. That would just be to satisfy the FCC. Then,
you have to deal with the FAA. In an area such as LA, with many airports, if
you moved the tower out of the Fullerton flight path, you would probably
have to place it in the flight path of another airport. Which doesn't solve
much. And even if it could be done, you would have to have additional
engineering studies to satisfy the FAA.

So, in all probability, the tower will be rebuilt in exactly the same place,
and at exactly the same height. Although I imagine they will add some
strobes when they rebuild it.

So, it's best to consider the tower much as you would a mountain, it's
there, it's on the charts, and it ain't going nowhere. And while the owners
and managers of KFI have been sleeping warm in their beds the last few
nights, a pilot and passenger have been sleeping cold in the morgue.

It's the pilot's responsibility to avoid the tower, period.

BTW, I am sure there are some ham guys and others who will find some
problems with my explanations; it's been 35 years since I've studied that
stuff, I'm sure there are some mistakes in there. So, if it's a serious
error, please bring it up, but let's not nit-pick over some relatively minor
and unimportant error, as so frequently happens in here...








"john smith" wrote in message
...
It will be interesting to see if they have to go through the application
process to put up a new tower at the same location.
It will be even more interesting to see if they apply for a taller tower.

G.R. Patterson III wrote:
Seems to me that this is an ideal opportunity for the station to add
those
lights, since they have to put up a new tower anyway.

In article , "Bill Denton"
writes:

Also, AM stations require a ground system, which is not required for FM or
TV stations. The ground system consists of a series of wires, buried
underground, each the length of the tower, and located at 10 degree (IIRC)
radials emanating from the tower base. Imagine the radials extending out
from a VOR every 1 degree, although these are not actual, physical, wire
radials. But for AM radio, these are actual wire radial, extending out every
10 degrees from the tower, with each radial the same length as the tower.
And you can't build anything on top of these radials, other than a small
transmitter building, as it will disrupt the signal. Which is why there is
always a large open area around AM towers that is not necessary, from a
broadcasting standpoint, for an FM or TV tower.

I don't know where you got this from. If you look at the arial pictures of the
KFI tower, you'll find that it is barely 100 feet away from industrial
buildings.

John

"JohnMcGrew" wrote in message
...
[...] The ground system consists of a series of wires, buried
underground, each the length of the tower, and located at 10 degree (IIRC)
radials emanating from the tower base. [...]
with each radial the same length as the tower.

I don't know where you got this from. If you look at the arial pictures
of the
KFI tower, you'll find that it is barely 100 feet away from industrial
buildings.

I don't know where he got it either. We live right next door to several
tall AM transmitting towers (at least three, maybe four...I'm too lazy to go
look out the window and refresh my memory), all of which are taller than the
distance between the antennas and our house (and dozens of other houses
around them too).

Maybe some AM towers have the radiating underground wires, but clearly not
all do.

"Peter Duniho" wrote

Maybe some AM towers have the radiating underground wires, but clearly not
all do.

Plus the fact, that on the ridge, the radiating wires would be running down
the side of mountain, and not at a 90 degree angle from the tower.
--
Jim in NC

If you have several AM towers closely grouped together, that is a
directional antenna array, which does use a different grounding system,
although I don't remember how it looks.

Since KFI is a clear-channel, non-directional station, it only has a single
tower, and does have the radial system I described. Perhaps I should have
been more clear about that.

Perhaps they now allow buildings on top of the buried radials, but I know it
was not common practice when I was in the broadcast business. The radials
eventually corrode and have to be replaced, which would be an extremely
expensive process if you had to knock down a bunch of buildings before you
did it.

If you are living that close to a tower, I would take a close look at my
deed to make sure there isn't an easement for the radials, allowing them to
do whatever to your house in order to replace them.

And I would also have somebody check out your house with an RF signal
strength meter; people worry about a 5 watt (or whatever) cell phone frying
their brain, just imagine what 50,000 watts is doing to you and your
family...




"Peter Duniho" wrote in message
...
"JohnMcGrew" wrote in message
...
[...] The ground system consists of a series of wires, buried
underground, each the length of the tower, and located at 10 degree
(IIRC)
radials emanating from the tower base. [...]
with each radial the same length as the tower.

I don't know where you got this from. If you look at the arial pictures
of the
KFI tower, you'll find that it is barely 100 feet away from industrial
buildings.

I don't know where he got it either. We live right next door to several
tall AM transmitting towers (at least three, maybe four...I'm too lazy to
go
look out the window and refresh my memory), all of which are taller than
the
distance between the antennas and our house (and dozens of other houses
around them too).

Maybe some AM towers have the radiating underground wires, but clearly not
all do.

Bill Denton wrote:


And I would also have somebody check out your house with an RF signal
strength meter; people worry about a 5 watt (or whatever) cell phone frying
their brain,

Your typical handheld cellphone is about 1/2 watt an inch from your brain.


just imagine what 50,000 watts is doing to you and your
family...

Do the math and figure out what signal strength there is where you
stand, plus low frequencies like the AM band are not what people are
worrying about.

And to think I use to fly 300 feet over the Voice of America
transmitters. WOW!!! That was lots of zots!
(Don't forget that signal strength falls off as the inverse square of
the distance.)

Newps wrote:
Bill Denton wrote:
And I would also have somebody check out your house with an RF signal
strength meter; people worry about a 5 watt (or whatever) cell phone
frying
their brain,

Your typical handheld cellphone is about 1/2 watt an inch from your brain.
just imagine what 50,000 watts is doing to you and you family...
Do the math and figure out what signal strength there is where you
stand, plus low frequencies like the AM band are not what people are
worrying about.

In article , "Bill Denton"
writes:

And I would also have somebody check out your house with an RF signal
strength meter; people worry about a 5 watt (or whatever) cell phone frying
their brain, just imagine what 50,000 watts is doing to you and your
family...

Not far from where I live, we have a 50kw AM transmitter litterally in the
middle of a shopping area. They had to use some particular shielding tricks on
the buildings to keep everything inside from being affected.

John

JohnMcGrew wrote:

Not far from where I live, we have a 50kw AM transmitter litterally in the
middle of a shopping area. They had to use some particular shielding tricks on
the buildings to keep everything inside from being affected.

Usually its so that when you turn off the floresent lights, they
actually do go off...