Fractenna wrote:
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.

73,
Chip N1IR
According to a article I read sometime ago the people that built the
BWMEWS system in Greenland used to stand in front of the antenna and
warm up.

Dave WD9BDZ

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

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

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

"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

"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

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.....

Me

"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

We recommend getting a vasectomy instead of microwaving yourself. Its less
painful, and cleaner.