"Yuri Blanarovich" wrote in message
...

Thierry wrote:
We know that during the emission of a radiotelescope (rare, for tests
or to send SETI msg, Hi!), the radiation can sterilize people working
in the dish.

Nonsense - we know nothing of the sort.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)

No-nonsense, it is sense. RF exposure causes temporary sterility, kinda
birth
control. Too much RF can cook us.

Yuri, K3BU.us


First, let's agree on nomenclature; a radio telescope is a receiving device
only, it is not an emitter. Feel free to coin a new term for a highly
directional, high power emitter used for astronomical research.

RF exposure can cause many things, from nothing sensible to boiling to
carbonization to vaporization. It all depends on the RF power, the
absorption and the time of exposure. Absorption is dependent on frequency
and conductivity of the sample. Heating is dependent on the power, the
absorption and the ability to transfer heat from the sample.

For instance, 14 GHz exposure will result in most radiation reflecting off a
human body; move the exposure to 2.4 GHz, and the effective depth of heating
will be several inches into the tissues. Move down to 960 MHz, and you will
get even deeper heating. (Consider why industrial microwave ovens are at 960
MHz.)

Some body tissues are more exposed to RF, and, having only modest blood
circulation, have a poor ability to transfer heat. Assuming you are male,
those tissues at risk would include your earlobes, fingertips, nose,
corneas, elbows, penis, scrotum, testicles and toes. Your earlobes, nose,
fingers and scrotum have good circulation, so the blood cooling helps to
protect them. Your toes are usually electrically close to the ground, and in
a region of lower power density. Your penis is also well cooled and poorly
exposed, unless RF exposure gives you a woodie. And who cares what happens
to your elbows? So that leaves your corneas and testicles as the most
vulnerable tissues.

Canadian Safety Code 6 is a well-written document that will also teach you a
lot about RF emissions, RF measurement and biological effects. It's limits
are based on old ANSI C95.3-1991 work, which has been codified as IEEE STD
C95.1-1999. The USA FCC also uses the IEEE standard. Both the IEEE and ANSI
want to charge you for access, but Industry Canada courteously provides a
free download at:

http://www.hc-sc.gc.ca/hecs-sesc/ccrpb/pdf/99ehd237.pdf

Thanks, Canada!

So we see that RF can do essentially nothing, it can sterilize, it can cook,
it can kill, and it can destroy. It's all a matter of power, frequency,
target and time.

Ed
wb6wsn

Yuri Blanarovich wrote:

Thierry wrote:
We know that during the emission of a radiotelescope (rare, for tests
or to send SETI msg, Hi!), the radiation can sterilize people working
in the dish.

Nonsense - we know nothing of the sort.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)

No-nonsense, it is sense. RF exposure causes temporary sterility, kinda birth
control. Too much RF can cook us.

TOO MUCH certainly can, and of course there are many documented cases.

It's Thierry's use of "we know" that bugs me. Does anyone actually
*know* of any case whe

People have been working in (inside) a radiotelescope dish
AND
The transmitter has been on (most radiotelescopes don't even have one)
AND
They have become sterile?

No, I thought not. That's because it's pure techno-folklore.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

Fractenna wrote:
A radar telescope--using a dish--can be dangerous and the EIRP can be
megawatts.

More techno-folklore.

The only heating power available is the power supplied up the feedline.
"Magnification" by the antenna is irrelevant, and EIRP figures only
serve to scare people.

Actually, the exact opposite is true. RF hazards are a function of power
density (mW/cm^2 or W/m^2). The higher the antenna gain is, and the
higher the far-field EIRP, the larger the aperture area must be and
therefore the lower the power density becomes.

The most dangerous antenna is the smallest, for example, an open-ended
waveguide or a small horn. That is because all the available power is
concentrated into such a small area. Looking into an open waveguide is
like looking into the barrel of a gun - you don't do it until you've
made darn sure about the other end!

But if you take that horn outside and mount it on a big dish where it's
hard to come anywhere near, it is immediately much safer. And the larger
the dish is, the smaller the RF hazard becomes.

Bottom line: "EIRP" and "RF hazard" don't belong in the same sentence -
except this one.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

A radar telescope--using a dish--can be dangerous and the EIRP can be
megawatts.

More techno-folklore.

The only heating power available is the power supplied up the feedline.


Well, why don't you go on the catwalk at Arecibo and see if they'll let you try
a little experiment while the radar is on.

I am speaking from knowledge, my friend.

73,
Chip N1IR

On Mon, 10 Jan 2005 09:09:35 +0000, "Ian White, G3SEK"
wrote:
Bottom line: "EIRP" and "RF hazard" don't belong in the same sentence -
except this one.

Hi Ian,

Even more remote is EIRP and nearness (EIRP demands the source appear
to be a point so that all phases from the reflector add to produce the
EIRP).

Another boner is that "a radio telescope is a receive-only device."
This bald statement would consign Arecibo to the ash heap of radio
telescopes because it has a 430 MHz radar system built into it. I
suppose by the same logic, a radar is a receive-only device between
pulses.

73's
Richard Clark, KB7QHC

Fractenna wrote:
A radar telescope--using a dish--can be dangerous and the EIRP can be
megawatts.

More techno-folklore.

The only heating power available is the power supplied up the feedline.


Well, why don't you go on the catwalk at Arecibo and see if they'll let
you try a little experiment while the radar is on.


It doesn't matter whether it's Arecibo or just an open waveguide, you
cannot ever be heated by more energy than is being supplied by the
transmitter.

The transmitter supplies all the available energy - there is no other
energy source involved - and it all comes out of the feedhorn. If you're
on the catwalk close to the feedhorn, and if there is enough energy,
then of course you'll feel it.

But that interaction involves only the transmitter, the feedhorn and
you. The dish and its gain have absolutely nothing to do with it. If the
dish were completely removed, you would still experience exactly the
same.

I am speaking from knowledge, my friend.

I know that you possess the knowledge; but that's not where you're
speaking from.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

"Fractenna" wrote in message
...
A radio telescope is a receive-only device. It is incapable of rendering
anything sterile.

A radar telescope--using a dish--can be dangerous and the EIRP can be
megawatts. In this case, a number of health dangers apply. Fortunately
those
most likely to be exposed are the best informed, and I am not familiar
with a
single case of dangerous exposure.

SETI has nothing to do with this.

Yes it does.
My post states in the case of the RT is used (was sued) to send SETI msg,
like to Arecibo and others.
Please believe, I know what I say.
http://www.astrosurf.com/lombry/menu-seti.htm

Thierry


73,
Chip N1IR

"Ian White, G3SEK" wrote in message
...
Fractenna wrote:
A radar telescope--using a dish--can be dangerous and the EIRP can be
megawatts.

More techno-folklore.

The only heating power available is the power supplied up the feedline.
"Magnification" by the antenna is irrelevant, and EIRP figures only
serve to scare people.

Actually, the exact opposite is true. RF hazards are a function of power
density (mW/cm^2 or W/m^2). The higher the antenna gain is, and the
higher the far-field EIRP, the larger the aperture area must be and
therefore the lower the power density becomes.

Ok Ian
I think that I can compute it now. I know the gain and MW sent by some RT,
the RF limits for the health, etc.

Thanks.
Thierry, ON4SKY



The most dangerous antenna is the smallest, for example, an open-ended
waveguide or a small horn. That is because all the available power is
concentrated into such a small area. Looking into an open waveguide is
like looking into the barrel of a gun - you don't do it until you've
made darn sure about the other end!

But if you take that horn outside and mount it on a big dish where it's
hard to come anywhere near, it is immediately much safer. And the larger
the dish is, the smaller the RF hazard becomes.

Bottom line: "EIRP" and "RF hazard" don't belong in the same sentence -
except this one.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

"Me" wrote in message
...
In article , "Thierry" - wrote:

We know that during the emission of a radiotelescope (rare, for tests or
to
send SETI msg, Hi!), the radiation can sterilize people working in the
dish.

If "We" know all this, "We" should not be in the dish when these test
are being conducted. Duhhhh.....


remark very useful to answer the question

Me

"Ian White, G3SEK" wrote in message
...
Yuri Blanarovich wrote:

...
It's Thierry's use of "we know" that bugs me. Does anyone actually
*know* of any case whe

People have been working in (inside) a radiotelescope dish
AND
The transmitter has been on (most radiotelescopes don't even have one)
AND
They have become sterile?

No, I thought not. That's because it's pure techno-folklore.


Where is the problem ? Folkore ? Non sense.
You never work with maths ?, you know, these kind of relaiton useless... on
the air.
but without which there hadn't had antennas either.

Why are you all so off-subject ? Is this so hard to answer a question.
It is more simple maybe to be involved in controversy... pfff


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek