How harmful is Wx radar?
Joined: May 2001
Posts: 1,267
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From: south of Cirencester, north of Lyneham
Graybeard,
Perhaps not 'modern', but years ago I worked on one that used a Travelling Wave Tube with 275kV on the collector, was 13 feet long, water cooled, and lived in a concrete pit lined with lead. Even with a .001% duty cycle, there was 5kW of RF, which would cook you!
When I did my radhaz course back in the '90s, we did an exercise on a 2MW S band radar of using a 'ball on a stick' to run along the waveguide looking for leaky joints. I found it was just as effective and quicker to run your hand along feeling for the spot where it was warm. A procedure heartily disapproved of officially by the lecturer!
Surprisingly, in pacemakers, where the battery power limits you to no more than 1mW out of the transmitter, you have to have some sort of small radome around the antenna to ensure you meet everybodies requirements on SAR. There we are talking generally of transmissions of a few seconds a month or less. becasue of battery life.
Perhaps not 'modern', but years ago I worked on one that used a Travelling Wave Tube with 275kV on the collector, was 13 feet long, water cooled, and lived in a concrete pit lined with lead. Even with a .001% duty cycle, there was 5kW of RF, which would cook you!
When I did my radhaz course back in the '90s, we did an exercise on a 2MW S band radar of using a 'ball on a stick' to run along the waveguide looking for leaky joints. I found it was just as effective and quicker to run your hand along feeling for the spot where it was warm. A procedure heartily disapproved of officially by the lecturer!
Surprisingly, in pacemakers, where the battery power limits you to no more than 1mW out of the transmitter, you have to have some sort of small radome around the antenna to ensure you meet everybodies requirements on SAR. There we are talking generally of transmissions of a few seconds a month or less. becasue of battery life.
Joined: May 2001
Posts: 1,267
Likes: 92
From: south of Cirencester, north of Lyneham
ChristiaanJ,
Remember that we are talking of a 10kW ERP pulse, with 20dB receiver antenna gain - and in all probability, antenna gain is nearer 30dB. So a perfect reflection at 200 miles would be around the -83dBm level into the receiver, even though the average power is very low. Given the signal processing gain available, it doesn't seem too unreasonable.
Remember that we are talking of a 10kW ERP pulse, with 20dB receiver antenna gain - and in all probability, antenna gain is nearer 30dB. So a perfect reflection at 200 miles would be around the -83dBm level into the receiver, even though the average power is very low. Given the signal processing gain available, it doesn't seem too unreasonable.
Joined: Jun 2005
Posts: 275
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From: Oxford, UK
Perhaps not 'modern', but years ago I worked on one that used a Travelling Wave Tube with 275kV on the collector, was 13 feet long, water cooled, and lived in a concrete pit lined with lead. Even with a .001% duty cycle, there was 5kW of RF, which would cook you!
When I did my radhaz course back in the '90s, we did an exercise on a 2MW S band radar
When I did my radhaz course back in the '90s, we did an exercise on a 2MW S band radar
Joined: Jun 2009
Posts: 1,344
Likes: 80
From: Bedford, UK
one opinion
http://www.ntsb.gov/Dockets/Aviation...076/403798.pdf
The following rules apply to the operation of aircraft radar equipment
while on the ground. In this context, "operation" means transmitting in
the "WX, TRB, TERR", position and does not include STBY, TEST, etc.
(1) Aircraft radar equipment shall not be operated while the aircraft is
being refueled.
(2) Aircraft radar equipment shall not be operated when another
aircraft, fuel truck, or other fueling equipment is within 50 feet
ahead or to either side of the nose.
(3) Aircraft radar equipment shall not be operated "nose on" to
another aircraft.
Note: Modem aircraft weather radar units typically transmit
about 70-80 watts of RF energy versus 50,000-75,000 watts
on older radars. The radar units in our aircraft fleet are
modern units, they do not pose a risk to humans, and they
comply with FAA Advisory Circular 20-68B. However,
despite safety to humans, it is prudent to comply with the
above restrictions to prevent possible damage to aircraft
equipment.
The following rules apply to the operation of aircraft radar equipment
while on the ground. In this context, "operation" means transmitting in
the "WX, TRB, TERR", position and does not include STBY, TEST, etc.
(1) Aircraft radar equipment shall not be operated while the aircraft is
being refueled.
(2) Aircraft radar equipment shall not be operated when another
aircraft, fuel truck, or other fueling equipment is within 50 feet
ahead or to either side of the nose.
(3) Aircraft radar equipment shall not be operated "nose on" to
another aircraft.
Note: Modem aircraft weather radar units typically transmit
about 70-80 watts of RF energy versus 50,000-75,000 watts
on older radars. The radar units in our aircraft fleet are
modern units, they do not pose a risk to humans, and they
comply with FAA Advisory Circular 20-68B. However,
despite safety to humans, it is prudent to comply with the
above restrictions to prevent possible damage to aircraft
equipment.
Joined: Jan 2005
Posts: 2,315
Likes: 10
From: France
Does not sound like something I would have gone and stood in front of.
But at this moment I'm just trying to gather a bit of data again in the context of this particular thread.... which seems to ignore just about everything... peak power versus average power of the transmitter, antenna gain, the fact whether the antenna is scanning or not, beam width, you name it.
Unfortunately the internet seems to have very little coherent
data.CJ
Joined: Dec 2006
Posts: 236
Likes: 1
From: belgium
There is a saying among our engineers that standing for too long in a beam will cause you to have female children only. And in fact, 9 at 10 of them in my company have daughters, so maybe some truth in there? I'd rather believe you will not get any children at all
Joined: Aug 2002
Posts: 1,320
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From: Switzerland, Singapore
slightly off topic. But you might be right. There is serious science trying to understand if it is possible to influence the gender of babies. There is one study that says that fathers with a sitting profession are more likely to have female babies, although not statistically significant. It might have a connection with the temperature of the father's sperm. Radar radiation might also induce higher temperatures.
As I said in an earlier post: microwave radiation doesn't work as radioactivity, so it doesn't primarly destroy the DNA, it just increases temperature in the affected tissue.
Dani
As I said in an earlier post: microwave radiation doesn't work as radioactivity, so it doesn't primarly destroy the DNA, it just increases temperature in the affected tissue.
Dani
Joined: May 2001
Posts: 1,267
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From: south of Cirencester, north of Lyneham
Way back when the world was young and the fields full of daisies and real beer was 1/3d a pint and even Watneys Red Barrel was palatable (yes it was - but they soon changed that!), radeng was an apprentice at Marconi in Chelmsford. It was noticeable and well known there that all the engineers working on high power transmitters always had daughters.
Only half a speed-brake
Joined: Apr 2003
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From: Commuting not home
Joined: Jun 2007
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From: Wanderlust
it’s less dangerous as standing in front of a microwave.
Joined: Jul 2006
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From: Somewhere over the rainbow
Hello Vilas,
I think this recommendations is just to be on the safe side as if we are not 100% sure it’s safe, then we must implement safety rules such as no cellphone during taxi and take off and landing. We all know this is horse !!!! but they still forbid us to use our phone.
For the weather radar, I know so cause I sent an Email to the manufacturer and they confirmed me it was not hazardous at all to humans.
Here’s the reply:
I think this recommendations is just to be on the safe side as if we are not 100% sure it’s safe, then we must implement safety rules such as no cellphone during taxi and take off and landing. We all know this is horse !!!! but they still forbid us to use our phone.
For the weather radar, I know so cause I sent an Email to the manufacturer and they confirmed me it was not hazardous at all to humans.
Here’s the reply:
Hi Gregory,
Sorry for my slow reply. I recently retired from Rockwell Collins and now work contract for them. So I am not regularly checking my email. In the past, with very old weather radars, it was common practice to turn off the radar whenever there was no significant weather because you quickly wore out the magnetron. Today's digital radars no longer use magnetrons and have a very long life. So we recommend having the radar on from push back to taxi in. With that said, over time there will be wear and tear on the gears and bearings in the pedestal. And although Rockwell Collins has a very low failure rate for these components, they are a mechanical system and are subject to failure. So some airlines elect to keep the radar off during operations to reduce the mechanical wear and tear.
And I think this was mentioned in the Cathay video, but the radar is a very minuscule radiation hazard... less than standing in front of a micorwave oven. So it is safe to turn it on during taxi.
Sincerely,
Steve
Sorry for my slow reply. I recently retired from Rockwell Collins and now work contract for them. So I am not regularly checking my email. In the past, with very old weather radars, it was common practice to turn off the radar whenever there was no significant weather because you quickly wore out the magnetron. Today's digital radars no longer use magnetrons and have a very long life. So we recommend having the radar on from push back to taxi in. With that said, over time there will be wear and tear on the gears and bearings in the pedestal. And although Rockwell Collins has a very low failure rate for these components, they are a mechanical system and are subject to failure. So some airlines elect to keep the radar off during operations to reduce the mechanical wear and tear.
And I think this was mentioned in the Cathay video, but the radar is a very minuscule radiation hazard... less than standing in front of a micorwave oven. So it is safe to turn it on during taxi.
Sincerely,
Steve
Joined: Apr 2008
Posts: 57
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From: UK
Some blurb from Rockwell Collins on their Multiscan Radar (150W by the way)
“The American National Standards Institute has specified a maximum level of 10mw/cm^2 for personal exposure of 6 minutes or longer to radar antenna electromagnetic radiation. The exposure time is limited to the amount of time within the antenna pattern during each sweep.......Microwave ovens represent a more public safety concern and their leakage standard has been set at 4mw/cm^2. The WXR-2100 power density is half or less than that of the microwave oven standard.”
Which backs up what Pineteam is saying. Now I’m not going to lie down on a radome while the radar is switched on any time soon, but I will be pretty relaxed about whether I’m going to get fried if the radar happened to get left on.
As a general rule, a while ago I read 50ft avoidance should cover pretty much most of the radars out there today.
“The American National Standards Institute has specified a maximum level of 10mw/cm^2 for personal exposure of 6 minutes or longer to radar antenna electromagnetic radiation. The exposure time is limited to the amount of time within the antenna pattern during each sweep.......Microwave ovens represent a more public safety concern and their leakage standard has been set at 4mw/cm^2. The WXR-2100 power density is half or less than that of the microwave oven standard.”
Which backs up what Pineteam is saying. Now I’m not going to lie down on a radome while the radar is switched on any time soon, but I will be pretty relaxed about whether I’m going to get fried if the radar happened to get left on.
As a general rule, a while ago I read 50ft avoidance should cover pretty much most of the radars out there today.
Joined: Jul 2014
Posts: 344
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From: Germany
Those distances are for being in front of the radar dish.
Isn't the more interesting figure how much radar energy there is in the cockpit from the weather radar? (none to speak of)
Also i get the impression people get confused mainly because it's "radiation".
Even without getting a sun burn, the light ("radiation" in the same sense as radar) from the sun will be much much more dangerous than the weather radar for pilots in the cockpit.
Isn't the more interesting figure how much radar energy there is in the cockpit from the weather radar? (none to speak of)
Also i get the impression people get confused mainly because it's "radiation".
Even without getting a sun burn, the light ("radiation" in the same sense as radar) from the sun will be much much more dangerous than the weather radar for pilots in the cockpit.
Avoid imitations
Joined: Nov 2000
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From: Wandering the FIR and cyberspace often at highly unsociable times
The Wx radar in the aircraft I fly is wired through a weight-on-wheels switch so it doesn't actually transmit on the ground.
Avoid imitations
Joined: Nov 2000
Aviation Qualifications: ATPL
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From: Wandering the FIR and cyberspace often at highly unsociable times
Psychophysiological entity
Joined: Jun 2001
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From: Walton on the Naze Essex.
The Wx radar in the aircraft I fly is wired through a weight-on-wheels switch so it doesn't actually transmit on the ground.
Taxiing out at JSY and being stopped adjacent to the radar head. Bzzzzz Bzzzzz Bzzzzz on the headphones and even little movements on the old moving coil instruments. Vasectomy a waste of time on those nights. Nah, more than a few nippers given the spark of life thanks to that myth.
https://www.who.int/peh-emf/publicat...acts/fs226/en/