Thierry wrote:

Hi,

I received this message from a colleague but I cannot answer him. I d
not know these systems.
Could you help me ?

My company has installed a Radar Tower for Port survaillence. The tower
is about 50 meter height on top of the of a 3 stories building roof and
my office building just below the tower on the same level, 20 meter away
from the tower. At the same time, the surrounding is my working area (
Jetty Terminal for ships loading and unloading activities ). I can say
that I'll be around that area 12 hours a day for another 20 years.

My question:

Is it safe to work in that area????

Thanks in advance
Thierry
http://www.astrosurf.org/lombry




So, what about Radar then...

First, There are two "kind" of RF radiation, non-ionizing and ionizing and
effects emanating from very high voltage nearby different materials.

Normally, non-ionising is to be more or less compared to sun light.
An overdose of non-ionising radiation gives the same effects than sun stroke
gives you, you heat up your body and the same symptoms occur if overheated.

As long as you are not overheating, there should be no harmful effects on
you. The problem are always to determine a narrow angle beam, radiating
towards sensitive parts of the body, like brain and eyes. The long term
effects of a heated brain are probably still debated. However, it's
probably not good for you. A narrow angle beam does not give the same full
body heating that "switches" your body reaction as it's only a part of you
that gets overheated, not the whole body!
If you are stupid enough to look into a wavegiude with full power on, be my
guest!

Now then to the nasty part, the ionising radiation. This radiation creates
residual effects even after the emitted radiation is switched off.
Typically radiation like Gamma radiation etc. This kind of radiation could
also create secondare types of radiation from materials in the environment.

Treat the ionising radiation like plague or cholera, avoid avoid avoid.


Now, radar radiation is only non-ionising RF radiation, let be with high
intermittent power and sometimes with stupidly high power.
Looking into an active waveguide will probably burn off your eye nerve or
something very bad for you.

If you are standing near a RF radiating radar station, the average energy is
what heats you up and the peaks are so short that even if they are Mega
Watts, the average energy transfer to your body is low.

Going up in frequency more or less moves the RF towards light, still with
the same effects.

OK, so it's not that bad is it? No? Wrong! Some frequencies are really bad
for us because different parts of our bodies absorbs different amount of
energy on different frequencies.

Let's take a party example... Many key fobs, alarm buttons for car locks
etc, operates on 418MHz. It happens to be approximately where a normal head
are resonating... Try walking just about out of range for your alarm/lock
button for your car, point the key fob against your head and press the
unlock key, voila, in most cases, you increase the range of the key fob.

So what? Just be aware and take a look in the health and safet chapter of
the ARRL handbook. It's all there and also how much more dangerous it is
with different frequencies.

The safest place are almost always under an antenna so don't fret over the
mobile phone mast on the roof of the school! I would be more concerned if
it was on a neighbouring house...


Cheers


Dan / M0DFI

Some thoughts inserted in Dan's comments...***


"Dan Andersson" wrote in message
...
Thierry wrote:
...
My company has installed a Radar Tower for Port survaillence. The tower
is about 50 meter height on top of the of a 3 stories building roof and
my office building just below the tower on the same level, 20 meter away
from the tower. At the same time, the surrounding is my working area (
Jetty Terminal for ships loading and unloading activities ). I can say
that I'll be around that area 12 hours a day for another 20 years.
My question:
Is it safe to work in that area????
Thanks in advance
Thierry

So, what about Radar then...

First, There are two "kind" of RF radiation, non-ionizing and ionizing and
effects emanating from very high voltage nearby different materials.

*** Perhaps a typo, but the ionizing type is not a kind of RF
radiation. Ionizing radiation is nuclear radiation. This radiation is able
to strip electrons (and other particles) from atoms. RF does not do this as
we use it. It is unfortunate that we use the term "radiation" for both
things. In any case, it is not part of the original question.


Normally, non-ionising is to be more or less compared to sun light....

*** RF, Light is Electromagnetic radiation and produces, as far as we
know and can be proved, Heat.



As long as you are not overheating, there should be no harmful effects on
you. ...

*** Widely agreed, yet feared by many.


Now, radar radiation ...sometimes with stupidly high power....

** Not to the people USING it.



If you are standing near a RF radiating radar station, the average energy
is
what heats you up ...

*** Regardless of where/how you receive RF power, it produces a heating
effect. Standing in an open field, you are picking up RF from EVERY
transmitter within ear-shot (so to speak) and you have RF currents in your
body, but of course, the heat generated is infinitesimal. Tests have been
done to measure the low, yet measurable actual heating of things such as the
human face in the RF field of hand-held radio like power.


Some frequencies are really bad
for us because different parts of our bodies absorbs different amount of
energy on different frequencies.

*** The effect is that of heating and the most prominant effect is the
heating of the water content in things - us included. Water (H20) absorbs
RF best around 900 MHz and again around 2500 MHz. There may be more
frequencies, but these are the two used in microwave ovens (900 earlier and
2400 now - I believe). When it does absorbe it ( as opposed to reflecting
it, which it may do depending on how good the impedance match is) the water
heats. The old (possibly urban myth) story is of the radar techs up at the
old Dew Line Early warning radars would stand in fornt of the High power
radar antennas to warm up when working outside. The standard joke is that
they had small families after that...



Let's take a party example... Many key fobs, alarm buttons for car locks
etc, operates on 418MHz. It happens to be approximately where a normal
head
are resonating... Try walking just about out of range for your alarm/lock
button for your car, point the key fob against your head and press the
unlock key, voila, in most cases, you increase the range of the key
fob....
Dan / M0DFI

*** Mine is around 320 MHz. I seriously doubt that the head resonates
there, or has much of a resonance to speak of at any frequency. This
"range extending of the keyless remote" is easily duplicated by various
placements of your other hand, arm and other parts of the body, near the
remote. I play with it often walking across the parking lot to the car. It
can be best explained considering that being conductive, the body can pick
up RF from the fob and be an added part of the antenna in a
quasi-parasitic-element manner. The "antenna" in the fob is, at best, an
extremely poor one (not being anywhere near 1/4 or 1/2 a wavelength, nor
being a loaded antenna that is matched to the transmitter) and any help it
gets will frequently be observed as positive. This effect is very dependant
on things like polarization of the auto's receive antenna (if there is one
with a recognizable polarization), polarization of "you as an antenna",
direction (as the transmit pattern will most certainly be directional as
well as the receive pattern), and probably innumerable other complexities of
the RF environment you happened to be immersed in.

Any kind of a conductor can be brought close to the fob and have a similar
effect. I've done it with long screwdrivers and pieces of wire. Careful
placement of a half wave wire can achieve astounding range....comparatively
(to me, anyway, but then, there are those that say I am easily amused).
Nerd that I am, it's fun to see how much range you actually can get...just
for the bleep of it. I should get a life at times. (:-) Please no
agreement.

73, Steve, K,9.D'C;I

Oh yea...the origainsl Radar near the office question. Do a search on
something like the Russian radar illumination of the American Embassy. I
believe there are those that claim the Americans which the Russians were
radiating with Radar got irritable or some such symptom(s).

73

Steve,

Your assertion is simply not correct. You may be thinking of particle
radiation, such as electron (beta), neutron, proton, alpha, cosmic,
etc., but pure photon radiation can certainly be "ionizing". A
well-known example is ordinary medical x-rays. Ionizing photons would
not typically be called "RF", but there is no difference other than the
energy levels.

(I spent so much time in the early stages of my career dealing with
intense sources of ionizing radiation (photons) that I still glow in the
dark.)

Back to the original question, ordinary radar is clearly not "ionizing".
Not a good idea to be too close, due to possible thermal effects, but
otherwise no big deal.

73,
Gene
W4SZ

Steve Nosko wrote:
Some thoughts inserted in Dan's comments...***


"Dan Andersson" wrote in message
...


First, There are two "kind" of RF radiation, non-ionizing and ionizing and
effects emanating from very high voltage nearby different materials.


*** Perhaps a typo, but the ionizing type is not a kind of RF
radiation. Ionizing radiation is nuclear radiation. This radiation is able
to strip electrons (and other particles) from atoms. RF does not do this as
we use it. It is unfortunate that we use the term "radiation" for both
things. In any case, it is not part of the original question.

Gene Fuller wrote:
..., but pure photon radiation can certainly be "ionizing".

My ITT "Reference Data for Radio Engineers" says gamma rays
are EM waves which are certainly "ionizing".
--
73, Cecil http://www.qsl.net/w5dxp

I think if it is too strong it will affect your eyes first, ears then
nerves/brain last. There are lots of safety precautions for wx radar on
aircraft and they are generally are under 10kw for small planes, x band
radar. Large jets, c band. Then there are fighter aircraft whose
targeting radar has been know to kill small animals around the runways.
But those are out of favour now, low power is in.



Thierry wrote:
Hi,

I received this message from a colleague but I cannot answer him. I d
not know these systems.
Could you help me ?

My company has installed a Radar Tower for Port survaillence. The tower
is about 50 meter height on top of the of a 3 stories building roof and
my office building just below the tower on the same level, 20 meter away
from the tower. At the same time, the surrounding is my working area (
Jetty Terminal for ships loading and unloading activities ). I can say
that I'll be around that area 12 hours a day for another 20 years.

My question:

Is it safe to work in that area????

Thanks in advance
Thierry
http://www.astrosurf.org/lombry

Steve Nosko wrote:

I don't understand being "on the same level" AND being "20 feet below".

Yes confusing, but I am sure there are intense lobes to look out for.

In article ,
Jules wrote:

I think if it is too strong it will affect your eyes first, ears then
nerves/brain last. There are lots of safety precautions for wx radar on
aircraft and they are generally are under 10kw for small planes, x band
radar. Large jets, c band. Then there are fighter aircraft whose
targeting radar has been know to kill small animals around the runways.
But those are out of favour now, low power is in.



Thierry wrote:
Hi,

I received this message from a colleague but I cannot answer him. I d
not know these systems.
Could you help me ?

My company has installed a Radar Tower for Port survaillence. The tower
is about 50 meter height on top of the of a 3 stories building roof and
my office building just below the tower on the same level, 20 meter away
from the tower. At the same time, the surrounding is my working area (
Jetty Terminal for ships loading and unloading activities ). I can say
that I'll be around that area 12 hours a day for another 20 years.

My question:

Is it safe to work in that area????

Thanks in advance
Thierry
http://www.astrosurf.org/lombry




The basic facts a Any commercial civilian Xband Radar will NOT even
come close to approching FCC RF Radiation Biologic Health Maximum
Radiation Power Densities even if you are right next to the antenna.
You are more likely to get hurt by the rotating antenna hiting you
in the head than from the RF Energy coming out of the antenna.
Wx Radar on Commecrcial Aircraft usually are left in Standby Mode
untill the aircraft has taxied onto the tarmac beside the active runway.
Eve if they were activated, most xBand versions still don't have the
Power Density one foot in front of the antenna to approch the FCC RF
Radiation Biologic Health Maximum.
Military Radars are a totally different beast altogether, and there are
very strict operational rules for when they can be operated inside US
Water and Airspace.

Me

Me wrote:

The basic facts a Any commercial civilian Xband Radar will NOT even
come close to approching FCC RF Radiation Biologic Health Maximum
Radiation Power Densities even if you are right next to the antenna.
You are more likely to get hurt by the rotating antenna hiting you
in the head than from the RF Energy coming out of the antenna.
Wx Radar on Commecrcial Aircraft usually are left in Standby Mode
untill the aircraft has taxied onto the tarmac beside the active runway.
runway
Eve if they were activated, most xBand versions still don't have the
Power Density one foot in front of the antenna to approch the FCC RF
Radiation Biologic Health Maximum.
Military Radars are a totally different beast altogether, and there are
very strict operational rules for when they can be operated inside US
Water and Airspace.

On my plane the radar is 7.6 kw (xband). The manual says not to use it
on the ground especially around people. Also they have been know to
cause some sort of sparking on metal so fuel trucks are to be avoided.
Shop people are cautioned to make sure it is not emitting if in stby
mode, some do. The display will say STBY, the antenna not panning, but
it is emitting. Go figure. Small airplanes have xband not because it is
wimpy but because of antenna size constraints. These are 10 ro 12 inch
diameter "flat dish" antennas. Lots of waveguide-like openings on it.
Extreemly directional. And this is a small 6 seater plane.

Large weather radars, ground based are sband. Big antennas.

In the late 80's many radars dropped down to under 10 watts. Most under
one watt. Mainly due to improved signal processing. Even on large jets
with large dishes. With the lower power came more managable attenuation
affects in rain too.

You do not want your head one foot away from my radar when it is on. And
I wouln't let you try it, even if you asked.

In article ,
Jules wrote:

Me wrote:

The basic facts a Any commercial civilian Xband Radar will NOT even
come close to approching FCC RF Radiation Biologic Health Maximum
Radiation Power Densities even if you are right next to the antenna.
You are more likely to get hurt by the rotating antenna hiting you
in the head than from the RF Energy coming out of the antenna.
Wx Radar on Commecrcial Aircraft usually are left in Standby Mode
untill the aircraft has taxied onto the tarmac beside the active runway.
runway
Eve if they were activated, most xBand versions still don't have the
Power Density one foot in front of the antenna to approch the FCC RF
Radiation Biologic Health Maximum.
Military Radars are a totally different beast altogether, and there are
very strict operational rules for when they can be operated inside US
Water and Airspace.

On my plane the radar is 7.6 kw (xband). The manual says not to use it
on the ground especially around people. Also they have been know to
cause some sort of sparking on metal so fuel trucks are to be avoided.
Shop people are cautioned to make sure it is not emitting if in stby
mode, some do. The display will say STBY, the antenna not panning, but
it is emitting. Go figure. Small airplanes have xband not because it is
wimpy but because of antenna size constraints. These are 10 ro 12 inch
diameter "flat dish" antennas. Lots of waveguide-like openings on it.
Extreemly directional. And this is a small 6 seater plane.

Large weather radars, ground based are sband. Big antennas.

In the late 80's many radars dropped down to under 10 watts. Most under
one watt. Mainly due to improved signal processing. Even on large jets
with large dishes. With the lower power came more managable attenuation
affects in rain too.

You do not want your head one foot away from my radar when it is on. And
I wouln't let you try it, even if you asked.




Jules, you really need to go back to Radar School and try and understand
the technology that your using. 7.6Kw Pulsed Xband Radars have an AVERAGE
Power of less than 20 watts. It isn't the Peak Pulse Power that fries
you, or causes the sparks, it is the AVERAGE Power, and less than 20
watts one foot in front of ANY antenna is considerably less than that,
due to RF Radiation being subject to the Inverse Square Law. Most of
the old Decca 20Kw Commercial Marine Radars in xBand had Average Powers
less that 35 watts, and were well below maximum Radiation Power
Densities directly in from of the 6ft Slotline Antennas.
Your socalled Flat Dish antennas at nothing more than a tuned Phase
Array, and again, one foot out in front, Power Densities are well
below maximum permissable Power Densities.

Third Generation Commercial xBand Radar Technology, that came in the
80's, introduced Solid State LNA's, Ring Circulating Isolators, and
Logrythemic IF ampilfiers, which improved the receivers Noise Figures,
and Dynamic Gain by an Order of Magnitude. This is all in the RF Path,
and had nothing to do with signal processing of baseband signals which
didn't come into play untill DSP Processors were intoduced in the mid
90's and the Fourth Generation of Commercial Radars.

Manuals are written by folks who understand the technology, about as
much as the lawyers, that approve them before they are published. Yes,
there are safety concerns with radar operations around FBO Fueling
Operations, but the incidents of actual causal problems, are rare to the
extreme.

Again, all the above is TRUE only for commercial radars, and may, or may
not be TRUE, and likely NOT TRUE for Military Radars, as these are more
often than not CW operating, and, or doppler type radars that are NOT
Pulsed.

Me

Me wrote:
7.6Kw Pulsed Xband Radars have an AVERAGE
Power of less than 20 watts.

I know it works in pulses and it is the pulse you should look out for.
Like a microwave oven , it can induce voltages in pieces of metal, high
enough to cause sparks. What would that do to a person with a pacemaker?

I only know the power rating.
I am not sure arcing incidents are that rare as I have met a couple of
people who claim to have seen it happen.

If a hammer drops on your foot and then rests there for 20 minutes, is
it the pulse or the average force to look out for.

My radar...

Peak Power Output: 7.5 KW nominal, 6.0 KW minimum

Output Frequency: 9375 Mhz (X-Band)

I think it does 160 pulses per second.



You would be willing to take the full brunt of that one foot away? I
will be back at the airport this afternoon and ask for someone to hold
thier head up to the radome. I never went to radar school.

I'll take your word for it, but I won't volunteer!