Is AM Radio Harmful?
 

This is a link to an article investigating leukemia rates in areas near AM
transmitters.

http://www.wired.com/news/medtech/0,1286,64579,00.html

I don't doubt that high levels of RF can be dangerous. The first two chief
engineers I worked with both died of cancer in their 50s.

Maybe they got cancer from some other cause (both smoked), but I still feel
like I'm inside a microwave oven anytime I'm around an AM transmitter site.

"lsmyer" wrote in message
...
This is a link to an article investigating leukemia rates in areas near AM
transmitters.

http://www.wired.com/news/medtech/0,1286,64579,00.html

I don't doubt that high levels of RF can be dangerous. The first two chief
engineers I worked with both died of cancer in their 50s.

Maybe they got cancer from some other cause (both smoked), but I still
feel
like I'm inside a microwave oven anytime I'm around an AM transmitter
site.




Wouldn't FM broadcast antennas be an even greater concern? The height of
most adults would make them resonant somewhere near, or in, the FM broadcast
band. I'd expect energy transfer to be more effiecnt from the FM broadcast
antenna to the human body than it is in the AM broadcast band.

Anyway, there's been over 80 years of kW+ levels of AM broadcasting, and it
seems strange this leukemia concern has gone unnoticed until now.

Frank Dresser

"lsmyer" wrote in message
...
This is a link to an article investigating leukemia rates in areas near AM
transmitters.

http://www.wired.com/news/medtech/0,1286,64579,00.html

I don't doubt that high levels of RF can be dangerous. The first two chief
engineers I worked with both died of cancer in their 50s.

Maybe they got cancer from some other cause (both smoked), but I still
feel
like I'm inside a microwave oven anytime I'm around an AM transmitter
site.

The thoroughly undocumented cases (no studies of groundwater contamination,
etc.) was based on the effects of stations with twice the power allowed in
the US on AMs.

Low levels of AM as experienced in the US would be very different.

"David Eduardo" wrote in message
...

The thoroughly undocumented cases (no studies of groundwater
contamination,
etc.) was based on the effects of stations with twice the power allowed in
the US on AMs.

Low levels of AM as experienced in the US would be very different.

While I think this whole thing is just another pseudo-science scare.... It
is NOT true that US stations have much lower field strength on AM. AFAIK,
very few foreign stations are directional at any power. Some US 50 kW
stations have pretty potent ERP in their beam. Not a megawatt, but quite a
bit nevertheless.

I'm a lot more worried about teens and others I see wandering around with a
cell-phone permanently attached less than an inch from their brain.

It's not the radiation. It's the hatred.

On 18 Aug 2004 14:15:19 GMT, "lsmyer" wrote:

This is a link to an article investigating leukemia rates in areas near AM
transmitters.

http://www.wired.com/news/medtech/0,1286,64579,00.html

I don't doubt that high levels of RF can be dangerous. The first two chief
engineers I worked with both died of cancer in their 50s.

Maybe they got cancer from some other cause (both smoked), but I still feel
like I'm inside a microwave oven anytime I'm around an AM transmitter site.

"Frank Dresser" wrote in message
...

Anyway, there's been over 80 years of kW+ levels of AM broadcasting, and
it
seems strange this leukemia concern has gone unnoticed until now.

Hi Frank,

Good point but compare to asbestos causing cancer where it can take 60 years
to appear.

I also often wonder what PCs are doing to us all staring at them all day,
we may be in for a big health shock in the years to come!

Also mobiles may ruin the brain. The consequences could be disastrous.

Happy thoughts!!

Cheers

Mike

On 18 Aug 2004 21:25:13 GMT, "Frank Dresser"
wrote:


"lsmyer" wrote in message
...
This is a link to an article investigating leukemia rates in areas near AM
transmitters.

http://www.wired.com/news/medtech/0,1286,64579,00.html

I don't doubt that high levels of RF can be dangerous. The first two chief
engineers I worked with both died of cancer in their 50s.

Maybe they got cancer from some other cause (both smoked), but I still
feel
like I'm inside a microwave oven anytime I'm around an AM transmitter
site.




Wouldn't FM broadcast antennas be an even greater concern? The height of
most adults would make them resonant somewhere near, or in, the FM broadcast
band. I'd expect energy transfer to be more effiecnt from the FM broadcast
antenna to the human body than it is in the AM broadcast band.

Anyway, there's been over 80 years of kW+ levels of AM broadcasting, and it
seems strange this leukemia concern has gone unnoticed until now.

Frank Dresser

It is another one of these cases where there may indeed be a link, but
there is no assurance at all that the link is causative. For example
you can find a link between smoking and cirrosis of the liver. Many
smokers are also significant drinkers. It wasn't the smoking that
caused the problem, but the smoking and other behaviours that are
causative are often seen together. I.E. most high power AM
transmitters are in major cities, and there are significant other
hazards from things like air pollution that exist independent of the
AM broadcast facilities.

As far as those working around the equipment, I'd be more interested
in the potential X-ray exposure. The voltages used in high power
transmitter tubes produce significant X-ray hazards, and these weren't
recognized for a long time.

there's been over 80 years of kW+ levels of AM broadcasting, and it seems
strange this leukemia concern has gone unnoticed until now.

....and to anyone who can actually read, there's no concern at all. The
so-called study offers no scientific proof whatsoever that proximity to AM
transmitters causes cancer. It's all number-crunching...the same kind of
bull-crap "science" which said that cyclamates were bad and eggs and meat would
kill you. Quoting statistics is not science.

Frank Dresser wrote:
Wouldn't FM broadcast antennas be an even greater concern? The height of
most adults would make them resonant somewhere near, or in, the FM broadcast
band. I'd expect energy transfer to be more effiecnt from the FM broadcast
antenna to the human body than it is in the AM broadcast band.

I'd sure think so.

On the other hand, the FM signal is radiated from an antenna atop the
tower. Stand at the base of a 300' FM tower, and you're 300' from the
thing that radiates.

At an AM station, the entire tower radiates.
--
Doug Smith W9WI
Pleasant View (Nashville), TN EM66
http://www.w9wi.com

In article , lsmyer wrote:

I don't doubt that high levels of RF can be dangerous. The first two chief
engineers I worked with both died of cancer in their 50s.

Maybe they got cancer from some other cause (both smoked), but I still feel
like I'm inside a microwave oven anytime I'm around an AM transmitter site.

These were folks who engaged in common engineering practices like soaking
a rag in carbon tetrachloride to clean PCB oil from failed capacitors out
of transmitter chassis, right? God knows we all did that sort of thing...
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

The RF energy could conceivably have an effect on cell membranes and the
potentials that develop across cell membranes. Perhaps some cells are more
sensitive to such changes in membrane potentials and lead to higher incidences
of certain diseases which in this case is leukemia.

As for not noticing the correlation for over 80 years that isn't so unusual. It
really is contingent on many factors including the increase in the number of
stations over the years, the increase in power over the years, the proximity of
the population to RF over the years (ie. the shift from a rural to an urban
population), the extent of the exposure, lifestyle and dietary changes and so on
and so on. It such a case it may take quite awhile to isolate a potential
causative agent and even then it wouldn't be overwhelmingly conclusive proof.
Too many variables to take into account.

Regards

John Barnard

Frank Dresser wrote:

"lsmyer" wrote in message
...
This is a link to an article investigating leukemia rates in areas near AM
transmitters.

http://www.wired.com/news/medtech/0,1286,64579,00.html

I don't doubt that high levels of RF can be dangerous. The first two chief
engineers I worked with both died of cancer in their 50s.

Maybe they got cancer from some other cause (both smoked), but I still
feel
like I'm inside a microwave oven anytime I'm around an AM transmitter
site.




Wouldn't FM broadcast antennas be an even greater concern? The height of
most adults would make them resonant somewhere near, or in, the FM broadcast
band. I'd expect energy transfer to be more effiecnt from the FM broadcast
antenna to the human body than it is in the AM broadcast band.

Anyway, there's been over 80 years of kW+ levels of AM broadcasting, and it
seems strange this leukemia concern has gone unnoticed until now.

Frank Dresser

"Doug Smith W9WI" wrote in message
...
Frank Dresser wrote:
Wouldn't FM broadcast antennas be an even greater concern? The height of
most adults would make them resonant somewhere near, or in, the FM broadcast
band. I'd expect energy transfer to be more effiecnt from the FM broadcast
antenna to the human body than it is in the AM broadcast band.

I'd sure think so.

On the other hand, the FM signal is radiated from an antenna atop the
tower. Stand at the base of a 300' FM tower, and you're 300' from the
thing that radiates.

At an AM station, the entire tower radiates.

One of the issues with most FM arrays with gain is that, for many, the spacing which
results in the array having gain also results in a fairly pronounced hot-spot
directly above the antenna, where few people would be expected to be, as well as
directly below, where technical personnel might spend a substantial amount of time.
Personally, I think that the AM radiation hazards are overstated in this study, and
that the issue comes more from environmental circumstances by virtue of the fact that
many AM transmitter installations share the same area as other industrial concerns.
--
-----------------------------------------------------------------------------
If there's nothing that offends you in your community, then you know you're not
living in a free society.
Kim Campbell - ex-Canadian Prime Minister - 2004
-----------------------------------------------------------------------------
For direct replies, take out the contents between the hyphens. -Really!-

"Doug Smith W9WI" wrote
On the other hand, the FM signal is radiated from an antenna atop the
tower. Stand at the base of a 300' FM tower, and you're 300' from the
thing that radiates.

At an AM station, the entire tower radiates.
___________

Also - most FM broadcast transmit antennas are arrays of several elements in
a vertical stack to concentrate radiation in the horizontal plane. As a
result the radiation directed around the tower base is much lower than the
station's licensed power.

RF

Visit http://rfry.org for FM broadcast RF system papers.

"Mike Terry" wrote in message
...

"Frank Dresser" wrote in message
...

Anyway, there's been over 80 years of kW+ levels of AM broadcasting, and
it
seems strange this leukemia concern has gone unnoticed until now.

Hi Frank,

Good point but compare to asbestos causing cancer where it can take 60
years
to appear.

Yes, but researchers can also sift through 80 years of public health
records. The people who have, or had, leukemia are known. It shouldn't be
hard to find out who lived near a radio transmitter and for how long. It
might be interesting to ask veterinarians about animal leukemia, since many
transmitters are located in rural areas.

But, since this story is being treated as news, I don't think there are even
any "rural legends" about a connection between leukemia and AM radio
transmitters.

Let's not forget that perfectly random chance is going to usually give us
lumpy results. A perfectly smooth map of leukemia cases would be something
like flipping a quarter ten times and getting exactly a h-t-h-t-h-t-h-t-h-t
result. It could happen, but any lumpy combination is just as likely, and
there are more lumpy combinations to go around.

Random chance alone might give us some leukemia hot spots. Some of those
hot spots might be near AM transmitters. It'll be interesting to see if
other leukemia hot spots are around AM radio transmitters, or if is just one
of those weird number things.


I also often wonder what PCs are doing to us all staring at them all day,
we may be in for a big health shock in the years to come!


Brother Stair used to say that the Internet was Satan's entryway into the
home. He seems to have softened his opposition lately. His website has a
page accepting donations using credit cards and paypal.



Also mobiles may ruin the brain. The consequences could be disastrous.

Mobiles as cellphones? Yes, there's no need to do studies to observe the
brain damage caused by those evil things. Just observe the cellphone addled
drivers as they careen from one close call to the next. The damage is
self-evident. Well, I don't need no stinkin' cellphone to damage my brain.

I'll stick with shortwave radio.


Happy thoughts!!

Cheers

Mike



Frank Dresser

"R J Carpenter" wrote in message
...

"David Eduardo" wrote in message
...

The thoroughly undocumented cases (no studies of groundwater
contamination,
etc.) was based on the effects of stations with twice the power allowed
in
the US on AMs.

Low levels of AM as experienced in the US would be very different.

While I think this whole thing is just another pseudo-science scare.... It
is NOT true that US stations have much lower field strength on AM. AFAIK,
very few foreign stations are directional at any power. Some US 50 kW
stations have pretty potent ERP in their beam. Not a megawatt, but quite
a
bit nevertheless.

the field strength of AM radio stations is measured in volts (microvolts)
not watts.

the field strength is inversely proportional to the square of the distance.

any study that relates any form of radiation, electromagnetic or otherwise
that does not refer to quantities measurements AND duration of exposure to
some other effect such as Leukemia is worthless.


I'm a lot more worried about teens and others I see wandering around with
a
cell-phone permanently attached less than an inch from their brain.

"R J Carpenter" wrote in message
...

I'm a lot more worried about teens and others I see wandering around with
a
cell-phone permanently attached less than an inch from their brain.


And their retinas as well..... 900 mhz --- I can recall around 20 years
ago (don't get on my case as to whether it was 16 or 22 or 18 years ago) but
the FCC advised the amateur radio community that if you don't do something
to increase your numbers, we're gonna have to start taking your VHF, UHF,
microwave allocations away. This spectrum is too valuable for you to hold
when your numbers are declining and you're not using them anyway.

They (FCC) discussed a codeless "communicator" license. The ARRL countered
with a "Novice Enhancement" program, which satisfied the Morse Code fetish
requirement, and, as it turned out, did not bring the 50,000 new hams
per year into the service as they claimed it would. But anyway, IIRC,
somebody's idea was to allow novices voice privileges on 902 Mhz, and it
was not considered seriously , and one of the reasons cited was safety.

"Richard Fry" wrote in message
...
___________

Also - most FM broadcast transmit antennas are arrays of several elements
in
a vertical stack to concentrate radiation in the horizontal plane. As a
result the radiation directed around the tower base is much lower than the
station's licensed power.

RF


Right, but often times there are a large number of people living in high
rise buildings near the FM antenna. It's conceivable there are more people
living in a high power FM radiation area than a high power AM radiation
area.

Frank Dresser

"Bob Haberkost" wrote
One of the issues with most FM arrays with gain is that, for many, the
spacing which
results in the array having gain also results in a fairly pronounced
hot-spot
directly above the antenna, where few people would be expected to be, as
well as
directly below...
_________________

This is true only when each element in the array has high relative field at
+/-90 degree elevation, and the elements are vertically spaced about one
wavelength apart. Shorter vertical spacings reduce such radiation from
these arrays. Using 1/2 wave spacing reduces it to a theoretical zero at
+/-90 degrees elevation (the zenith and nadir).

BUT, the great majority of FM broadcast transmit elements used today have
elevation patterns with very low relative field at +/90 degrees. An array
of such elements also has low relative field at +/-90 degrees -- even with
elements spaced at one wavelength intervals. IOW, no hot-spots above and
below the array.

Patterns of four element types in common use today, and an elevation pattern
for a 6-element, 1-wave-spaced array of one type are included in the PDF
slide show listed as Paper 10 at http://rfry.org.

RF

"Frank Dresser" wrote
... often times there are a large number of people
living in high rise buildings near the FM antenna. It's
conceivable there are more people living in a high power
FM radiation area than a high power AM radiation.
________________

Could happen in the odd case, but not usually. FM broadcast transmit
antennas located on building tops normally have radiation center heights
that easily clear the tops of nearby buildings. If they didn't, the
station's signal would be affected by shadowing (blockage) beyond the nearby
buildings, and have widespread multipath problems from reflections off the
building sides. Competitive issues make this situation unlikely.

RF

The answer to your questions are right here in the FCC's OET56


http://www.fcc.gov/Bureaus/Engineeri...56/oet56e4.pdf



"lsmyer" wrote in message
...
This is a link to an article investigating leukemia rates in areas near AM
transmitters.

http://www.wired.com/news/medtech/0,1286,64579,00.html

I don't doubt that high levels of RF can be dangerous. The first two chief
engineers I worked with both died of cancer in their 50s.

Maybe they got cancer from some other cause (both smoked), but I still
feel
like I'm inside a microwave oven anytime I'm around an AM transmitter
site.

lsmyer wrote:

This is a link to an article investigating leukemia rates in areas near AM
transmitters.

http://www.wired.com/news/medtech/0,1286,64579,00.html

I don't doubt that high levels of RF can be dangerous. The first two chief
engineers I worked with both died of cancer in their 50s.

Maybe they got cancer from some other cause (both smoked), but I still feel
like I'm inside a microwave oven anytime I'm around an AM transmitter site.




AM Radio is harmful only if you listen to it.

In article ,
R J Carpenter wrote:

is NOT true that US stations have much lower field strength on AM. AFAIK,
very few foreign stations are directional at any power.

Particularly in Europe, few stations even have vertical radiators.

-GAWollman

--
Garrett A. Wollman | As the Constitution endures, persons in every
| generation can invoke its principles in their own
Opinions not those of| search for greater freedom.
MIT, LCS, CRS, or NSA| - A. Kennedy, Lawrence v. Texas, 539 U.S. ___ (2003)

Buzzygirl wrote:
"Greg and Joan" wrote:
But anyway, IIRC,
somebody's idea was to allow novices voice privileges on 902 Mhz, and it
was not considered seriously , and one of the reasons cited was safety.

There is still no commercially-available equipment for the 902 MHz amateur
band that I am aware of.

Using commercially-available equipment is cheating anyway. What does it
take to modify PCS cellular phone firmware for digital communication on
902? Is it just a matter of firmware or isn't the RF section able to tune
that far out of band?
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

In rec.radio.shortwave Frank Dresser wrote:

Right, but often times there are a large number of people living in high
rise buildings near the FM antenna. It's conceivable there are more people
living in a high power FM radiation area than a high power AM radiation
area.

And the government exposure limits are more stringent at the FM
frequencies (30 to 300 MHz).

See:
http://www-training.llnl.gov/wbt/hc/...Standards.html

Art N2AH

It is another one of these cases where there may indeed be a link, but
there is no assurance at all that the link is causative. For example
you can find a link between smoking and cirrosis of the liver. Many
smokers are also significant drinkers. It wasn't the smoking that
caused the problem, but the smoking and other behaviours that are
causative are often seen together. I.E. most high power AM
transmitters are in major cities, and there are significant other
hazards from things like air pollution that exist independent of the
AM broadcast facilities.

Therefore, smoke as many cigarettes as you want to, and if you get lung cancer,
just blame it on the air pollution.

Perhaps when I walk into a fire, the blistering burns all over my skin are caused
from the chemicals in the sun tan lotion I used the day before.

Voting for Nader or Badnarik is somehow taking a vote away from Kerry, but no one
ever suggests Bush and Kerry drop out of the race because they are taking votes
away from the other two. Ridiculous.

Yes, but researchers can also sift through 80 years of public health
records. The people who have, or had, leukemia are known. It shouldn't be
hard to find out who lived near a radio transmitter and for how long. It
might be interesting to ask veterinarians about animal leukemia, since many
transmitters are located in rural areas.

Do you really need to have people smoke cigarettes for 80 years before you agree
that inhaling smoke into your lungs is going to cause health problems?

These are all basic things we should know without having to go through decades
of health records to figure out.

I knew in 1983 that Aspartame was a horror, yet only now are people starting to
figure that out.

Let's not forget that perfectly random chance is going to usually give us
lumpy results. A perfectly smooth map of leukemia cases would be something
like flipping a quarter ten times and getting exactly a h-t-h-t-h-t-h-t-h-t
result. It could happen, but any lumpy combination is just as likely, and
there are more lumpy combinations to go around.

Same with trying to link lung problems with smoking. But can you seriously
say that breathing smoke into your lungs is not going to cause health
problems? Just use common sense.

Random chance alone might give us some leukemia hot spots. Some of those
hot spots might be near AM transmitters. It'll be interesting to see if
other leukemia hot spots are around AM radio transmitters, or if is just one
of those weird number things.

While you do all that, I will just avoid living next to any AM or FM radio
transmitters. I wish I could do the same with Microwave Cellular towers, but
that is getting impossible to avoid today.

I also often wonder what PCs are doing to us all staring at them all day,

LCD screens are obviously much safer and healthier than the CRT screens. Do
we really need studies on that too, or can we all use common sense to figure
that one out as well?

Brother Stair used to say that the Internet was Satan's entryway into the
home.

Satan is make-believe.

Also mobiles may ruin the brain. The consequences could be disastrous.

May?!

Mobiles as cellphones? Yes, there's no need to do studies to observe the
brain damage caused by those evil things.

Exactly.

I don't doubt that high levels of RF can be dangerous. The first two chief
engineers I worked with both died of cancer in their 50s.

Wouldn't FM broadcast antennas be an even greater concern? The height of
most adults would make them resonant somewhere near, or in, the FM broadcast
band.

Comparing wavelengths of "people" based on their height is ridiculous.
Microwaves are a much shorter wavelength and cause much more damage to the human
body, so the wavelength of people based on their height theory needs to be
thrown out right away.

I'd expect energy transfer to be more effiecnt from the FM broadcast
antenna to the human body than it is in the AM broadcast band.

This is like the argument that you should vote for the lesser of two evils,
rather than vote for a good candidate.

Why choose to live near an AM or FM broadcast antenna? I would not want to
live next to either. What is more annoying is how cellular telephone
antennas are getting to be impossible to avoid, and new ones are being put up
every week.

Anyway, there's been over 80 years of kW+ levels of AM broadcasting, and it
seems strange this leukemia concern has gone unnoticed until now.

80 years is only one generation of people. Give it time. Old time radio
commercials have doctors endorsing cigarettes that are healthy and good for you
and your throat.

Cell phones have not been in use long enough for the evidence to exist to
convince those that don't have the radio background to know how dangerous they
are now, without needing to see several generations of people suffer from them
first.

Aspartame is only now starting to get the attention that I was aware of decades
ago.

Now we have Sucralose (not sucrose) and Ace K, and again, we will have to wait
around 20 years or longer before enough people have suffered to start to
consider them a health threat.

On the other hand, the FM signal is radiated from an antenna atop the
tower. Stand at the base of a 300' FM tower, and you're 300' from the
thing that radiates.

This is the same theory in which people claim using their cell phones are safe,
because the power they put out is so low.

They are powerful enough to transmit to cell towers miles away! Now put that
power inches from your head and how more concentrated is that power?

"Truth" wrote in message ...

80 years is only one generation of people. Give it time. Old time
radio
commercials have doctors endorsing cigarettes that are healthy and good
for you
and your throat.


Definition time:

"Generation, interval of time between the birth of parents and the birth of
their offspring. This is usually taken to be approximately 30 years. All
children of one set of parents are members of the same generation although
they may be years apart in age
© 1993-2003 Microsoft Corporation. All rights reserved.

"Scott Dorsey" wrote in message
...
Buzzygirl wrote:
"Greg and Joan" wrote:
But anyway, IIRC,
somebody's idea was to allow novices voice privileges on 902 Mhz, and
it
was not considered seriously , and one of the reasons cited was safety.

There is still no commercially-available equipment for the 902 MHz
amateur
band that I am aware of.

Using commercially-available equipment is cheating anyway. What does it
take to modify PCS cellular phone firmware for digital communication on
902? Is it just a matter of firmware or isn't the RF section able to tune
that far out of band?
--scott


could be things have changed without me noticing but i dont think digital
PSC type stuff is allowed for hams... maybe in experimantal bands?
in the poplar comm freqs it just FM, ssb, AM, CW, a little FSK, some packet,
a little SSTV, some full TV (usully in conjuction with emergancy support
operations)

anything encrypted or encoded was a big no-no

There is still no commercially-available equipment for the 902 MHz amateur
band that I am aware of.

Using commercially-available equipment is cheating anyway. What does it
take to modify PCS cellular phone firmware for digital communication on
902? Is it just a matter of firmware or isn't the RF section able to tune
that far out of band?

Think of it this way. When you have an FM broadcast antenna and transmitter, it
makes quite a difference when switching within the same band from 88 Mhz to 100
Mhz. (only 12 Mhz)

Now you want to take something from around 850 Mhz to 902 Mhz (52 Mhz
difference)

Plus the higher up you go, the more critical the circuitry. Even in the 440
band you are already dealing with microsurgery when using the miniature surface
mount components.

Besides, working with microwaves is never a good idea. Might as well just take
up smoking cigarettes instead.

I would play with mercury and use lead paint in my home no problem, but I would
not ever build a transmitter and use microwave frequencies.

Go to http://tx.mb21.co.uk/gallery/ and look at some of their AM/MW
sites. Not only do many of them still use those cool T-shaped
horizontal wire antennas, but in some shots you can see sheep grazing in
the fields very close by. The RF foes in the USA should consult with
veterinarians in the UK and see what their research comes up with

GTT




Truth wrote:
Yes, but researchers can also sift through 80 years of public health
records. The people who have, or had, leukemia are known. It shouldn't be
hard to find out who lived near a radio transmitter and for how long. It
might be interesting to ask veterinarians about animal leukemia, since many
transmitters are located in rural areas.

(snip)

"Truth" wrote in message ...
On the other hand, the FM signal is radiated from an antenna atop the
tower. Stand at the base of a 300' FM tower, and you're 300' from the
thing that radiates.

This is the same theory in which people claim using their cell phones are
safe,
because the power they put out is so low.

They are powerful enough to transmit to cell towers miles away!

and that proves? ... nothing


Now put that
power inches from your head and how more concentrated is that power?



why not look it up?

you will find that a 5 watt transmitter operating on 450 MHz with a 1/4 wave
antenna might produce enough heating to damage the cornea of the eye IF the
tip is placed within one CM of the eye.

--- "REC.RADIO.BROADCASTING Moderator Mailbox"
wrote:

On 22 Aug 2004, misterfact wrote:


If the radio waves themselves aren't harmful-
certainly the constant
barrage of medical mis-information from AM radio
talk show hosts- can
be harmful if followed!

Kindly refrain from hijacking unrelated discussion
threads to make your
point. This will not be posted.

--
rec.radio.broadcasting is moderated by Steve Sobol,


The topic was: Is AM radio harmful?

Certainly my reply was not related to any physical
harm which might result from radio waves themselves-
but since the message board has to do with radio
broadcasting in general- I thought it would be a good
opportunity to inject ANOTHER TYPE OF MEDICAL HARM
which I see inherent in AM broadcasting today.

I will continue to take a look at the threads in this
post and see if conjecture or humorous , slightly off
the subject comments are part of it. (which seems to
be pretty much standard throughout google message
boards.)

I hope you will show as much concern for threatening
language and 4 letter words- as you did my post.

However in the future- I will do a better job at
sticking to the subject at hand.
Sincerely, Mike Cohrman






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"Truth" wrote in message ...
On the other hand, the FM signal is radiated from an antenna atop the
tower. Stand at the base of a 300' FM tower, and you're 300' from the
thing that radiates.

This is the same theory in which people claim using their cell phones are
safe,
because the power they put out is so low.

They are powerful enough to transmit to cell towers miles away! Now
put that
power inches from your head and how more concentrated is that power?

In rec.radio.shortwave Truth wrote:
I don't doubt that high levels of RF can be dangerous. The first two chief
engineers I worked with both died of cancer in their 50s.

Wouldn't FM broadcast antennas be an even greater concern? The height of
most adults would make them resonant somewhere near, or in, the FM broadcast
band.

Comparing wavelengths of "people" based on their height is ridiculous.
Microwaves are a much shorter wavelength and cause much more damage to the human
body, so the wavelength of people based on their height theory needs to be
thrown out right away.

To oversimplify a bit: Low frequencies (like AM broadcast) pass through
the body without being absorbed. Microwave frequencies bounce off the body
without being absorbed. It's the frequency range between 30 and 300 MHz
where maximum absorption takes place.

Art H.

And the government exposure limits are more stringent at the FM
frequencies (30 to 300 MHz).

Every government has different limits, rules and laws. So this is MEANINGLESS!

As if moving to a different country somehow makes the exposure more or less safe
than being in another country.

Never go by government information.

One road along side homes in my area is 55 mph, while another road with no homes
or buildings on it is 25 mph.

What does that prove? That the government is made up of bozos and idiots.

What if the government issues a statement that smoking cigarettes is good for you
and gets rid of cholesterol? Would you start smoking?

"Bob Haberkost" wrote
Huh? AM stations essentially always have vertical radiators,
especially in Europe where there are so many high powered
stations. In general, AMs don't work very well otherwise.

H-Pol radiators have little to no ground wave.

H-pol would not be used on VHF and above (FM/TV broadcast etc) if that was
true. A linear, horizontal dipole antenna at MW or any other band generates
its maximum field strength at all angles perpendicular to its longitudinal
centerline -- which includes all angles from below the antenna out to the
radio horizon; i.e., a "ground" wave. [Free-space radiation with respect to
the dipole itself is the same whether its axis is horizontal or vertical.]

The reason h-pol is not used for MW is because path losses are much higher
for h-pol than v-pol in that part of the radio spectrum.

This is why a vertical radiator is sometimes called a "ground plane"
antenna, snip for those installations on the ground, this counterpoise
is usually buried.

The radial ground system used with MW broadcast antennas reduces antenna
system losses (I^2R), and keeps maximum radiation directed more toward the
the horizontal plane, rather than at some elevation angle above the
horizontal. The FCC defines the minimum efficiency of radiators licensed
for MW broadcast in terms of producing a field strength of so many mV/m at 1
km from the antenna, per kW of antenna input power. These efficiencies
cannot be met without using a good ground system.

Those familiar with 11-meter Citizens Band know this antenna
in its 27MHz form, snip the reason why this particular configuration has
these radials at a 45-degree angle from the horizontal is because a ground
plane
antenna has an intrinsic impedance of about 30 ohms....the farther towards
being
vertical, the more it's like a dipole, with a dipole's characteristic 72
ohm
impedance. Thus, at 45 degrees or so, the ground planes typically used
for C-Band
are about 50 ohms without the need for a matching network.)

Possibly more important is the point that drooping the radials also tends to
lower the angle of maximum radiation, which can improve field strength for
receiving antenna sites at/near ground level.

The nice thing about the low radiating impedance of a vertical radiator is
that the
high base current necessary for a given power means that the magnetic
vector is
bigger than the electrostatic vector, and since ferrite loops used in most
AM radios
respond to the magnetic vector, the "connection" is more intimate.

?? The table below shows the efficiencies for MW vertical radiators with a
good ground system. The self-impedance of a 90 degree vertical is about 50
ohms, and for a 180 degree vertical it is over 100 ohms. So for the same
input power, base current is lower in a 180 degree radiator than in a 90
degree radiator. Yet the efficiency of the 180 degree radiator is higher --
the opposite of the above quote statement.

The ground wave field strength of a MW vertical radiator per kilowatt of
input power is related only to the current distribution in the radiator, not
its base impedance. Whatever the base impedance is, it can be matched to 50
ohm line at the tower base, using the right network. But the network doesn't
affect the relative field radiation pattern of that radiator.

AM Radiator Efficiencies, 1kW input
(for equal distances)

Twr Hgt, Deg Effic
70 182mV/m
90 190
100 195
180 237
190 246
225 274

Note here that "efficiency" is the FCC definition for MW broadcast.
Efficiency falls for short radiators because the ohmic loss even in the best
ground system becomes a bigger percentage of the resistive term of the
radiators base impedance.

RF

Visit http://rfry.org for FM broadcast RF system papers.

"Truth" wrote in message ...
There is still no commercially-available equipment for the 902 MHz
amateur
band that I am aware of.

Using commercially-available equipment is cheating anyway. What does it
take to modify PCS cellular phone firmware for digital communication on
902? Is it just a matter of firmware or isn't the RF section able to
tune
that far out of band?

Think of it this way. When you have an FM broadcast antenna and
transmitter, it
makes quite a difference when switching within the same band from 88 Mhz
to 100
Mhz. (only 12 Mhz)

Now you want to take something from around 850 Mhz to 902 Mhz (52 Mhz
difference)

yes but 88 to 100 = 12 percent of final freq

850 to 902 is only 5.765 per cent



Plus the higher up you go, the more critical the circuitry. Even in
the 440
band you are already dealing with microsurgery when using the miniature
surface
mount components.

Besides, working with microwaves is never a good idea. Might as well
just take
up smoking cigarettes instead.

I would play with mercury and use lead paint in my home no problem, but I
would
not ever build a transmitter and use microwave frequencies.

"Truth" wrote in message ...
There is still no commercially-available equipment for the 902 MHz
amateur
band that I am aware of.

Using commercially-available equipment is cheating anyway. What does it
take to modify PCS cellular phone firmware for digital communication on
902? Is it just a matter of firmware or isn't the RF section able to
tune
that far out of band?

Think of it this way. When you have an FM broadcast antenna and
transmitter, it
makes quite a difference when switching within the same band from 88 Mhz
to 100
Mhz. (only 12 Mhz)

Now you want to take something from around 850 Mhz to 902 Mhz (52 Mhz
difference)

Plus the higher up you go, the more critical the circuitry. Even in
the 440
band you are already dealing with microsurgery when using the miniature
surface
mount components.

pretty might the same for all hand held electronics these days


Besides, working with microwaves is never a good idea.

everyone has to have a hobby... 900 MHz are NOT microwaves (we call it
microwave in brroadcast, but it is a slang term for high UHF)

Might as well just take
up smoking cigarettes instead.

I would play with mercury and use lead paint in my home no problem, but I
would
not ever build a transmitter and use microwave frequencies.


gunplexers are friendly... bi-directional line-of-sight audio