There are undoubtedly official sources from the FCC, etc.

The best hand-held guide I could recommend would be the National Radio
Club's "Night Pattern Book," a fantastic resource for MW DXers and
broadcast listeners. Basically it is a book of maps of North America
for each domestic broadcast frequency, with dots representing
transmitting locations, and the night time radiation pattern around each.

It's available from the following link:

http://www.nrcdxas.org/catalog/books/

The 5th edition is sold out, but the new 2005-06 edition is scheduled to
be out soon.

Brent Taylor
VE1JH


Dave Pitzer wrote:
Richard,

Both you and Reg have given excellent answers and I thank you both.

By the way, you mention directional patterns and nulls. Is there any place I
can find polar graphs of commercial broadcast station's antenna patterns?

Thanks,

Dave P.

There are undoubtedly official sources from the FCC, etc.

The best hand-held guide I could recommend would be the National
Radio
Club's "Night Pattern Book," a fantastic resource for MW DXers and
broadcast listeners. Basically it is a book of maps of North
America
for each domestic broadcast frequency, with dots representing
transmitting locations, and the night time radiation pattern around
each.

It's available from the following link:

http://www.nrcdxas.org/catalog/books/

The 5th edition is sold out, but the new 2005-06 edition is
scheduled to
be out soon.

Brent Taylor
VE1JH


Dave Pitzer wrote:
Richard,

Both you and Reg have given excellent answers and I thank you
both.

By the way, you mention directional patterns and nulls. Is there
any place I
can find polar graphs of commercial broadcast station's antenna
patterns?

Thanks,

======================================
Dave,

http://www.nrcdxas.org/catalog/books/
Sounds exactly what you are looking for but may take some time to
obtain.

In the meantime, the basic groundwave radiation patterns of mediumwave
broadcast antennas are either simple circles with the antenna at their
centres, or heart-shaped with the antenna at the null.

The first occurs when the antenna is a single vertical mast located
near the centre of a large populated area.

The second occurs when the antenna consists of a pair of masts, which
radiate a very broad heart-shaped beam, located on one side of the
populated area to be covered.

Contour Maps of actual measured field strengths are useful when the
basic groundwave patterns are distorted by the terrain, e.g., the
existence of mountains, forests, rivers, built-up areas, high-rise
cities, or seas, lakes or coastal regions.

Radio frequency Field Strengths are usually measured in terms of
"millivolts per meter" or in decibels relative to one volt per meter.
----
Reg.

snip
In the meantime, the basic groundwave radiation patterns of mediumwave
broadcast antennas are either simple circles with the antenna at their
centres, or heart-shaped with the antenna at the null.

The first occurs when the antenna is a single vertical mast located
near the centre of a large populated area.

The second occurs when the antenna consists of a pair of masts, which
radiate a very broad heart-shaped beam, located on one side of the
populated area to be covered.
snip
----
Reg.



Reg:

I'm afraid you're way behind the practice on this one. In the US, there are
many 4, 5 and 6 tower arrays providing as many nulls to protect co-channel
stations. The UK got off easy with nationalized broadcasting, where the
frequency and location was dictated by the government, and none of that
nasty capitalism interfered. Here, the commercial interests are still
fighting it out. Check and see if the KLIF website shows their pattern from
a linear array of 5 towers just outside Dallas.

--
Crazy George
W5VPQ
My real address is my ham call atARRL.NET The ATTGlobal is a SPAM trap.

"Crazy George" wrote
I'm afraid you're way behind the practice on this one. In the US,
there are
many 4, 5 and 6 tower arrays providing as many nulls to protect
co-channel
stations.

=================================

What proportion of US MF broadcasting stations have antennas
consisting of more than two towers ?
----
Reg.

Reg, G4FGQ wrote:
"What proportions of U.S. broadcasting stations have antennas consisting
of more than two towers?"

I don`t know but from my own experience, the number is large. A new
applicant for a station must show he will not interfere with existing
stations by limiting his radiation in the directions of the existing
stations while providing minimum field intensity, 0.5 to 50 mV,
depending on population, in the new service area. A two-tower array
cannot satisfy some complicated pattern requirements.

Most broadcasters want to provide more than 1 KW radiation in their
areas. Well over one hundred channels in the medium wave broadcast band
in North America allow that. There are well over 1000 regional medium
wave broadcasters in North America. It is difficult to fit a new
broadcaster in when he wants to use real power.

Best regards, Richard Harrison, KB5WZI

Richard Harrison wrote:
I don`t know but from my own experience, the number is large.

I would guess that the majority of US AM antennas that I
have seen with my own eyes have more than one element.
--
73, Cecil http://www.qsl.net/w5dxp

Reg:

I don't have an accurate number for the entire country, but here in the
local area, there is one clear channel station with a single radiator, a
half dozen two tower arrays, two 3 tower arrays, five 4 tower arrays that I
can recall off the top of my head. If you had asked a dozen years ago, I
could have been more accurate. I don't think we have any 5 or 6 radiator
arrays here locally, if so, I don't remember them. If my math is correct,
that is a 50-50 split, so maybe half have more than 2 towers.

--
Crazy George
W5VPQ
My real address is my ham call atARRL.NET The ATTGlobal is a SPAM trap.
"Reg Edwards" wrote in message
...

"Crazy George" wrote
I'm afraid you're way behind the practice on this one. In the US,
there are
many 4, 5 and 6 tower arrays providing as many nulls to protect
co-channel
stations.

=================================

What proportion of US MF broadcasting stations have antennas
consisting of more than two towers ?
----
Reg.

"Crazy George" wrote
I don't have an accurate number for the entire country, but here in
the
local area, there is one clear channel station with a single
radiator, a
half dozen two tower arrays, two 3 tower arrays, five 4 tower arrays
that I
can recall off the top of my head. If you had asked a dozen years
ago, I
could have been more accurate. I don't think we have any 5 or 6
radiator
arrays here locally, if so, I don't remember them. If my math is
correct,
that is a 50-50 split, so maybe half have more than 2 towers.

=======================================

Thanks George,

I am amazed at the number of multi-tower MF antennas in the US. As you
say, they are necessary to prevent co-channel interference, day and
night, between a large number of broadcasters in the more densely
populated regions of your vast country. ( Antenna salesmen have had a
field day.)

It is also interesting that the whole system is technically regulated
by State and/or Central Government. It is not just a free-for-all for
newcomers.

I imagine the revenue comes solely from advertisers. Which makes me
wonder what percentage of program time is allocated to adverts. Are
such matters also regulated? Are any broadcast stations State or City
owned?

In this (UK) relatively densely populated country things settled down
about 20 years ago. Few MF antennas have more than one tower (or masts
as we call them). Although there is much broadcasting at MF for
individual cities, most broadcasting takes place at FM VHF where
'capture effects' reduce interference from co-channel transmitters.

It may be of interest that the BBC, still the World's finest
broadcasting system, including its overseas services, no longer owns
any transmitting stations, Mrs Thatcher quietly sold them off to a
private party. Do some Googles for who the eventual owners are?
----
Reg.

Reg Edwards wrote:

SNIPPED


I imagine the revenue comes solely from advertisers. Which makes me
wonder what percentage of program time is allocated to adverts. Are
such matters also regulated? Are any broadcast stations State or City
owned?

$$$ from advertisers ... YEP!

Amount of advertising time is regulated. I can't state with any
authority, but it seems to be 15 to 20 minutes per hour.

Ownership is generally private. International propaganda, err news, may
be indirectly government controlled through a straw man corporation.
Certain public service stations, e.g. WWV, are government 'owned'.

An several additional non sequitor comments. In the USA, although we
claim FREE ENTERPRISE, it is a government influenced economy via
interest rates, international treaties, anti-trust regulations, etc.

Finally, the USA is succumbing to a creeping Socialism. This is contrary
to the words of John F Kennedy: "Ask NOT what your country can do for
you; ask what you can do for your country." Forty-five years after that
statement from President Kennedy a large portion of the population want
the government to do everything for them.

A Keag


In this (UK) relatively densely populated country things settled down
about 20 years ago. Few MF antennas have more than one tower (or masts
as we call them). Although there is much broadcasting at MF for
individual cities, most broadcasting takes place at FM VHF where
'capture effects' reduce interference from co-channel transmitters.

It may be of interest that the BBC, still the World's finest
broadcasting system, including its overseas services, no longer owns
any transmitting stations, Mrs Thatcher quietly sold them off to a
private party. Do some Googles for who the eventual owners are?
----
Reg.

Reg, G4FGQ wrote:
"It is also interesting that the whole system is technically regulated
by State and/or Central Government."

In the beginning, there was no regulation. There were only wireless
experimenters. Marconi invented the antenna which made the signal go
far. Marconi`s antenna may have been seen as an elevated capactor plate.
When the transmitter and receiver were each equipped with a plate, you
had a coupling capacitor with the earth for a return path. The capacitor
carries displacement current while the earth moves electrons.. Then,
Marconi discovered the capacitor leads worked well enough without the
plates, so plates were omitted.

Marconi was soon using wireless for ship to shore communications. It was
essential to safety of life at sea. When the Titanic sank on April 15,
1912, it had a Marconi operator aboard. The world was immediately aware
of radio. Inept radio communications during the loss of the Titanic
prompted the U.S. Congress to pass the Radio Act of 1912, which expanded
on the Wireless Ship Act of 1910 which required all seafaring vessels to
maintain 24-hour radio watch and keep contact with nearby ships and
coastal radio stations.

All radio communications were in code until Reginald Fessenden invented
wireless telephony in 1906. In the early wireless days a lidtener had to
understand code to make sense of wireless.

The Radio Act of 1912 assigned three-letter and four-letter codes
(call-letters) to radio stations and limited broadcasting to 340 meters.
This jammed the signals. From the beginning, the U.S. Federal Government
declared sole jurisdiction over radio as the waves don`t stop at state
lines and must involve international cooperation. It`s the "Interstate
Commerce Regulation Power" of the Federal Government.

In 1920, KDKA in Pittsburgh, a Westinghouse station, transmitted the
first commercial radio broadcast.

In 1922, the U.S. Commerce Department allowed powerful stations to use
400 meters, as long as they only broadcast music.

In 1925, A,C. Nielsen began reporting audience shares to advertisers,

In 1925, the first soap opera (The Smith Family) was broadcast.

In 1926, RCA, General Electric, and Westinghouse established The
National Broadcasting Company (NBC). NBC operated two networks of
stations (Red & Blue).

In 1929, William S. Paley founded The Columbia Broadcasting System
(CBS).

In 1931, there were 40,000 U.S. TV sets, including 4,000 in New York
City.

In 1933, Edwin Armstrong introduced Frequency Modulation.

The Communications Act of 1934 created the Federal Communicationsd
Commission which regulates broadcasting.

In 1936, The British Broadcasting Corporation (BBC) debuted the world`s
first television service with three hours of programming a day.

In 1937, Edgar Bergen and Charlie MCCarthy debuted on NBC TV.

We live in interesting times.

Advertising pays for broadcasting in the U.S. except for some public
support of non-commercial or almost non-commercial stations.

Program time devoted to advertising on commercial stations was limited
by the FCC to just a few minutes per hour before Carter became
president. He started the deregulation process which has now run amok.
Commercial announcements were the topic of "Saturday Night Live".
Satirically, they entertain.

Mrs. Thatcher may have sold the BBC`s distribution facilities, but since
BBC has done so well programming, I hope the production facilities are
still in the hands of those responsible and that they continue and grow
their product.

Who bought the BBC`s transmitters depends on how big the bargains were.
If a windfall was readily available, I suspect the Queen, her relatives
and allies may have been the buyers. Like Russia, I suppose, except with
more care that the buyers seem not to be profiteers.

My daughter lives in London and pays her tax to support the BBC. She now
owns a 99-year lease on her flat in Westminster. Only leases are
available. The right people are the ownwers and they aren`t selling. Her
married name is Edwards too, but her husband is an American. They are
both lawyers.

Best regards, Richard harrison, KB5WZI