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.

"Tom Ring" wrote in message
.. .
Richard Harrison wrote:

very well.

Best regards, Richard Harrison, KB5WZI


Slight change of subject, WCCO 830 and a couple others I've noticed, now
have a tremendous amount of digital sounding crap around them that
completely obscures stations such as KOA. Is this the new digital radio
wonder weapon that I'm supposed to love?

tom
K0TAR


You bet!!!!

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

Thanks to you all for your excellent information

DP


"Dave Pitzer" wrote in message
...
Why is it that I can received WCBS @ 880kc fairly well at night but WABC @
770kc suffers from phase distortion like you wouldn't believe! (I'm about
175 miles from both transmitters.) They are both 50 kwatt stations. And
why
is it that both WBZ (Boston), WBT (Charlotte, NC), WJR (Detroit) and WBBM
(Chicago) come in better than either of the New York City stations?

Dave P.

"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

"Dave Pitzer" wrote
... Is there any place I can find polar graphs of commercial
broadcast station's antenna patterns?

___________________

Dave,

Here http://www.radio-locator.com/ is a link to a website with calculated
coverage areas/contours for US AM broadcast stations. The contours are
based on their licensed radiation patterns (directional or not), AND ground
conductivities for the geographic regions concerned.

The polar radiation patterns of these stations most probably don't look much
like these plots, because of the heavy influence that ground conductivity
has on received field strength along the various azimuth bearings.

Even the real coverage contours of AM broadcast stations using omni antennas
usually are anything but omni, due to the effects of varying ground
conductivities around their various azimuth sectors and ranges.

Have fun.

RF

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.