JT_76 0 #1 September 17, 2006 Me and some friends were having a crazy discussion about skydiving the other day and we're split on who's right and who's wrong. Somehow the topic of illegal ailens sneaking into the country came up and one guy says he could get them in easily by renting a plane in Mexico and doing a tandem skydive. He reasoned he could just have the pilot go over the border about 10-15 miles, drop him and his passenger off at 10-12,000ft and then turn around and fly back into Mexico. He claims that yes the authorities would know an aircraft just entered illegally but they wouldn't know someone jumped out of it and he would just have a vehicle waiting on the ground and take off. Me and another guy think that not only would they know a plane entered illegally, they would also be able to tell that someone or something jumped/fell out of it and track his progress to the ground. But then again the Special Forces use this type of method to get behind ememy lines without detection so maybe he could get away with it. Maybe he wouldn't show up until the chute opened and there was a bigger profile? Anyone know for sure? We have some beer riding on it so hopefully someone here knows something about radar! Quote Share this post Link to post Share on other sites
Ron 7 #2 September 17, 2006 Yes, radar can "see" skydivers. The return is small and most would ignore it, and a solo might not be noticed, but I don't know for sure. However, folks I know that work for the FAA have told me that largish formations (12-16 ways) are pretty easy to see. QuoteHe reasoned he could just have the pilot go over the border about 10-15 miles, drop him and his passenger off at 10-12,000ft and then turn around and fly back into Mexico They could also just walk across like they do now. The plane would attract attention."No free man shall ever be debarred the use of arms." -- Thomas Jefferson, Thomas Jefferson Papers, 334 Quote Share this post Link to post Share on other sites
Merkur 1 #3 September 17, 2006 If you know what to look for, you can detect us. M.vSCR No.94 Don't dream your life - live your dream! Quote Share this post Link to post Share on other sites
Eule 0 #4 September 17, 2006 QuoteMe and another guy think that not only would they know a plane entered illegally, they would also be able to tell that someone or something jumped/fell out of it and track his progress to the ground. Apparently, ATC RADAR can see jumpers when adjusted correctly. QuoteMaybe he wouldn't show up until the chute opened and there was a bigger profile? I'm not sure all that nylon would show up very well on the RADAR. It probably doesn't care about the difference between belly-to-earth and standing up (under canopy) much, but if you're flying towards the RADAR while under canopy, it might have a better chance of picking up the metal bits of the harness. EulePLF does not stand for Please Land on Face. Quote Share this post Link to post Share on other sites
Sockpuppet 0 #5 September 17, 2006 Havent you watched that 100% factual film "Dropzone". Man, your so stupid its all to do with the metal! Its easy when you start modding containers with what looks like parts of seat belts, and black. All equipment must be black. ------ Two of the three voices in my head agree with you. It might actually be unanimous but voice three only speaks Welsh. Quote Share this post Link to post Share on other sites
KrisFlyZ 0 #6 September 17, 2006 I am not sure if this is true but someone said that when we were doing wingsuit formations at Skydive Deland 2004 the ATC(Daytona Beach?) was picking us up. Kris. Quote Share this post Link to post Share on other sites
DZJ 0 #7 September 17, 2006 Apparently the CRW 85-way started showing up on local radars from 30+. (If I recall an article in the BPA magazine correctly) Quote Share this post Link to post Share on other sites
cocheese 0 #8 September 18, 2006 I asked an Army guy at Quincy who was doing air traffic control for the convention. He said "Yes, that's how we time the loads so good." And they ARE awesome at controlling the airspace. Quote Share this post Link to post Share on other sites
matthewcline 0 #9 September 18, 2006 During the GA state record attempts a few years ago ATL ATC could see the big "blot" on the screen. They would tell the Pilots, according to the end of day beer discussions.An Instructors first concern is student safety. So, start being safe, first!!! Quote Share this post Link to post Share on other sites
BlindBrick 0 #10 September 18, 2006 Quote I'm not sure all that nylon would show up very well on the RADAR. It has something to do with the dense air trapped in the cells. And it takes a certain amount of it. Conversations with our pilots and the local ATC seem to indicate that you need a 260+ sf canopy to generate a return. -Blind"If you end up in an alligator's jaws, naked, you probably did something to deserve it." Quote Share this post Link to post Share on other sites
JohnMitchell 14 #11 September 18, 2006 QuoteQuote I'm not sure all that nylon would show up very well on the RADAR. It has something to do with the dense air trapped in the cells. And it takes a certain amount of it. Conversations with our pilots and the local ATC seem to indicate that you need a 260+ sf canopy to generate a return. I'm calling Bullshit on that one! Air is transparent to radar, as well as most plastics, such as nylon. But depending on the radar, a small amount of metal will produce a return, such as cable housings, buckles, etc. A techie could tell you much more. I work ATC radar everyday, but our primary (raw) radar is heavily filtered. It would be hard to tell skydivers from random ground clutter. The approach control radar, though, is more sensitive. Quote Share this post Link to post Share on other sites
Mr17Hz 1 #12 September 18, 2006 QuoteQuoteQuote I'm not sure all that nylon would show up very well on the RADAR. It has something to do with the dense air trapped in the cells. And it takes a certain amount of it. Conversations with our pilots and the local ATC seem to indicate that you need a 260+ sf canopy to generate a return. I'm calling Bullshit on that one! Air is transparent to radar, as well as most plastics, such as nylon. But depending on the radar, a small amount of metal will produce a return, such as cable housings, buckles, etc. A techie could tell you much more. I work ATC radar everyday, but our primary (raw) radar is heavily filtered. It would be hard to tell skydivers from random ground clutter. The approach control radar, though, is more sensitive. It doesn't matter that air is transparent to radar. Radar produces electromagnetic fluctuations in the 'radio wave' frequency. For radar to work signals are reflected. The time it takes for the signal sent to return indicates distance, and the doppler shift in the frequency is measured to determine the approximate velocity of the object. Any surface that is ridged is more likely to reflect radio frequency. Air pressure inside of a canopy causes the nylon itself to become extremely taught; and the overall surface to become a flat plain. That tautness will cause more of a signal to be reflected; and the flat surface means that the reflection of the radio signal will be more dense and measurable... so yes, a deployed parachute would increase the chances of being seen on radar.Matt Christenson [email protected] http://www.RealDropzone.com - A new breed of dropzone manifest software. Quote Share this post Link to post Share on other sites
jbrasher 0 #13 September 18, 2006 Be careful out there, radar can cause cancer, too! Red, White and Blue Skies, John T. Brasher D-5166 Quote Share this post Link to post Share on other sites
darkwing 4 #14 September 18, 2006 QuoteIt doesn't matter that air is transparent to radar. Radar produces electromagnetic fluctuations in the 'radio wave' frequency. For radar to work signals are reflected. The time it takes for the signal sent to return indicates distance, and the doppler shift in the frequency is measured to determine the approximate velocity of the object. Any surface that is ridged is more likely to reflect radio frequency. Air pressure inside of a canopy causes the nylon itself to become extremely taught; and the overall surface to become a flat plain. That tautness will cause more of a signal to be reflected; and the flat surface means that the reflection of the radio signal will be more dense and measurable... so yes, a deployed parachute would increase the chances of being seen on radar. I'm more inclined to go for the aggregate metal a skydiver has than any funny business with the nylon and air. So says the physicist in me, who is also quite willing to get educated with real values of aircraft radar reflectivity at air density gradients. If air density gradients did it, then I think stealth planes wouldn't be stealthy, because they have hellacious air density gradients around them. The stealth trickery is in other things (surface composition and contours). As before, I'd be glad to be re-educated. -- Jeff My Skydiving History Quote Share this post Link to post Share on other sites
Zenister 0 #15 September 18, 2006 properly calibrated radar can detect the differences between specular and non-specular returns from nearly any 'reflective' surface. Its mostly a matter of having enough resolution avail in the area while the formation is exposed at optimal angles. most skydiving activities would generally fall in the realm of clutter, but could still be observed.____________________________________ Those who fail to learn from the past are simply Doomed. Quote Share this post Link to post Share on other sites
lekstrom10k 0 #16 September 18, 2006 We used to jump at Salem Airport Michigan in 1972-76. The controllers at Detroit Approach Control prided themselves on how many they counted flying to the formation, they only got confused when we launched a two ir three way. If you look at a flight chart and see a magenta circle (pink) around an airport with numbers near it . Thats telling you the bottom of their visibilty range. and they cant see you Scud Run there, it veries with ground clutter.If they could do it then imagine now. Quote Share this post Link to post Share on other sites
wildblue 4 #17 September 18, 2006 I want to take a big roll of foil on a cross-country with me. Or would that get me shot down?it's like incest - you're substituting convenience for quality 1 Quote Share this post Link to post Share on other sites
squirrel 0 #18 September 18, 2006 "According to the Surgen General, Radar is in use and can cause cancer" This is what is going to be posted at DZs out here in California! ________________________________ Where is Darwin when you need him? Quote Share this post Link to post Share on other sites
matthewcline 0 #19 September 18, 2006 I was at a DZ in TN and it was posted in a plane and on the ground.An Instructors first concern is student safety. So, start being safe, first!!! Quote Share this post Link to post Share on other sites
squirrel 0 #20 September 18, 2006 really, actually warning skydivers...or the gernal public at an airport? ________________________________ Where is Darwin when you need him? Quote Share this post Link to post Share on other sites
matthewcline 0 #21 September 18, 2006 It is a tongue in cheek comment at a DZ. We took a controller up for a jump 2 weekends ago and he thought it was funny to see the sign in the plane. He also told us he could track individuals as long as he was not watching other traffic, so on non UT home game weekends he would watch the jumpers for hours.An Instructors first concern is student safety. So, start being safe, first!!! Quote Share this post Link to post Share on other sites
vskydiver 0 #22 September 18, 2006 Quote If you look at a flight chart and see a magenta circle (pink) around an airport with numbers near it . Thats telling you the bottom of their visibilty range. and they cant see you Scud Run there, it veries with ground clutter. Ummm, sorry, that's incorrect. The magenta circle incicates a control zone, or now called class E surface area. That's the legal description of the type of airspce at the airport's surface. There is no marking on the pilot's chart that tell him the radar coverage. Sometimes it to the ground, sometimes doesn't start until 10,000 feet or higher in some remote airports out west. Scud running we don't really care about if you do it legally. But that's why the control zones, to keep scud runners out of higher density IFR operation areas. Quote Share this post Link to post Share on other sites
JohnMitchell 14 #23 September 18, 2006 QuoteBe careful out there, radar can cause cancer, too! You are joking, right? Very unlikely for radar to cause cancer. It's lower frequency, non-ionizing radiation, actually lower frequency than the heat lamp in the bathroom or the light bulb in your reading lamp. The higher frequency, ionizing radiation, think UV on up into xray and gamma, cause the chemical changes that may lead to cancer. Quote Share this post Link to post Share on other sites JohnMitchell 14 #24 September 18, 2006 Quote It doesn't matter that air is transparent to radar. Radar produces electromagnetic fluctuations in the 'radio wave' frequency. For radar to work signals are reflected. so yes, a deployed parachute would increase the chances of being seen on radar. Interesting hypothesis. Do you have any proof? Why do I not see giant plastic research ballons on my radar scope, then. I've worked dozens of missions with them at Tillamook, OR. Your talk of how radar works is correct, although mine doesn't use the Doppler effect, but to say that something is transparent to radar but also a good reflector sounds illogical. However, I have observed temperature inversions bending radar (think mirages) but that is much different than reflecting radar. Quote Share this post Link to post Share on other sites Mr17Hz 1 #25 September 18, 2006 QuoteQuote It doesn't matter that air is transparent to radar. Radar produces electromagnetic fluctuations in the 'radio wave' frequency. For radar to work signals are reflected. so yes, a deployed parachute would increase the chances of being seen on radar. Interesting hypothesis. Do you have any proof? Why do I not see giant plastic research ballons on my radar scope, then. I've worked dozens of missions with them at Tillamook, OR. Your talk of how radar works is correct, although mine doesn't use the Doppler effect, but to say that something is transparent to radar but also a good reflector sounds illogical. However, I have observed temperature inversions bending radar (think mirages) but that is much different than reflecting radar. What I am saying is that in general terms - air does not effect radio waves (this is actually untrue, particles in the air do but as a level that takes it out of the scope of this conversation). However, if air causes another material that would reflect radio waves (nylon) to take a different physical shape (in this case making it a flat plane) then the originally very weak and scattered reflection becomes more concentrated and it is more likely that a receiver looking for the signal is able to pick it up. Technically speaking, all radar technology needs to consider the Doppler effect. Radio waves are everywhere, from every directions. Even your cell phone emits a signal that travels forever if nothing absorbs it. The further away from the transmitter, the more spread out the electromagnetic radiation becomes, causing the signal to be more difficult to identify. In order to transmit and receive signals with accuracy, radio technology as we know it uses a carrier frequency and different forms of modulation. The most common knowledge modulation types are AM (Amplitude Modulation) and FM (Frequency Modulation). Radar radio doesn't need to carry any more information than is necessary to be able to identify itself when listening to the echo. If you bounce a certain frequency (using unproportional figures for simplicity) off of an object that is not moving at say 10MHz - your echo will be 10MHz. However if that object is moving away from you, the frequency becomes slower - lets say 9.9MHz. If that object is moving closer to you, the frequency becomes faster at 10.1MHz. This is the Doppler effect, and can also be noticed with sound (the textbook example is when a police car drives past you, the siren on his car changes tone slightly from a high pitch, to a lower pitch) Again, these numbers are for the sake of example... the actual change would be much much smaller. A radar can't take a "snapshot" to detect anything. It requires time to work. Radio frequency is quite high, you can receive 100 million wavelengths a second - so from our perspective it seems to work instantly - but it needs to receive the signal for long enough to lock on to the carrier frequency, and then determine small changes in frequency. This is all done with analog electronics because digital computers of today are not powerful enough to make this calculations. Various techniques can be used to assist in making sense of weak signals. One of these is to look for patterns that would represent signals reflecting off of a flat surface that was not at an exact 90 degree angle. These types of analog circuits are commonplace in electronics; but are most commonly implemented in the design of the antenna. The round nature of a balloon is not something most receivers are designed to accomodate (not that it couldn't but it would be a lot of extra unnecessary engineering for most common radar practices). This would explain why an inflated parachute would be more likely to be picked up than a weather balloon. It all comes down to what a particular radar was designed to look for. ATC radar systems may or may not be able to pick up single skydivers. I would be surprised if they did, as they're looking for larger items. They have a larger chance of being able to see a deployed ram-air parachute. The point that I was trying to make is that the air pressure inside of a ram air canopy *would* indirectly make a physical difference in a radar being able to detect that parachute because air is what is giving the parachute a close-to-flat surface, and that most radios are designed to receive signals being sent from (antennas) or reflecting off of (airplanes) relatively flat surfaces. As any radio expert would tell you, what I wrote above isn't 100% accurate from the perspective that I left a lot out about concepts involved in receiving signals... But that was my best job of explaining why the air inside of a ram-air canopy would contribute to the entire parachute becoming easier to see on a radar than if it was not inflated. - without writing a book on radio. While I'm not a professional with radio (I've never made money doing it), about 5 years ago I actually built a radio that I used to measure the distance between the earth and moon by reflecting signals off it. and, It was only a 5 watt transceiver. My original intention was to make a clock that would teach itself what time it was over a few days time based on light changes, and measuring the position and distance of the moon... I only got as far as measuring the distance between the earth and moon before I got bored with the project. Took me about 2 weeks of free time.Matt Christenson [email protected] http://www.RealDropzone.com - A new breed of dropzone manifest software. 1 Quote Share this post Link to post Share on other sites Prev 1 2 Next Page 1 of 2 Join the conversation You can post now and register later. If you have an account, sign in now to post with your account. Note: Your post will require moderator approval before it will be visible. 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JohnMitchell 14 #24 September 18, 2006 Quote It doesn't matter that air is transparent to radar. Radar produces electromagnetic fluctuations in the 'radio wave' frequency. For radar to work signals are reflected. so yes, a deployed parachute would increase the chances of being seen on radar. Interesting hypothesis. Do you have any proof? Why do I not see giant plastic research ballons on my radar scope, then. I've worked dozens of missions with them at Tillamook, OR. Your talk of how radar works is correct, although mine doesn't use the Doppler effect, but to say that something is transparent to radar but also a good reflector sounds illogical. However, I have observed temperature inversions bending radar (think mirages) but that is much different than reflecting radar. Quote Share this post Link to post Share on other sites
Mr17Hz 1 #25 September 18, 2006 QuoteQuote It doesn't matter that air is transparent to radar. Radar produces electromagnetic fluctuations in the 'radio wave' frequency. For radar to work signals are reflected. so yes, a deployed parachute would increase the chances of being seen on radar. Interesting hypothesis. Do you have any proof? Why do I not see giant plastic research ballons on my radar scope, then. I've worked dozens of missions with them at Tillamook, OR. Your talk of how radar works is correct, although mine doesn't use the Doppler effect, but to say that something is transparent to radar but also a good reflector sounds illogical. However, I have observed temperature inversions bending radar (think mirages) but that is much different than reflecting radar. What I am saying is that in general terms - air does not effect radio waves (this is actually untrue, particles in the air do but as a level that takes it out of the scope of this conversation). However, if air causes another material that would reflect radio waves (nylon) to take a different physical shape (in this case making it a flat plane) then the originally very weak and scattered reflection becomes more concentrated and it is more likely that a receiver looking for the signal is able to pick it up. Technically speaking, all radar technology needs to consider the Doppler effect. Radio waves are everywhere, from every directions. Even your cell phone emits a signal that travels forever if nothing absorbs it. The further away from the transmitter, the more spread out the electromagnetic radiation becomes, causing the signal to be more difficult to identify. In order to transmit and receive signals with accuracy, radio technology as we know it uses a carrier frequency and different forms of modulation. The most common knowledge modulation types are AM (Amplitude Modulation) and FM (Frequency Modulation). Radar radio doesn't need to carry any more information than is necessary to be able to identify itself when listening to the echo. If you bounce a certain frequency (using unproportional figures for simplicity) off of an object that is not moving at say 10MHz - your echo will be 10MHz. However if that object is moving away from you, the frequency becomes slower - lets say 9.9MHz. If that object is moving closer to you, the frequency becomes faster at 10.1MHz. This is the Doppler effect, and can also be noticed with sound (the textbook example is when a police car drives past you, the siren on his car changes tone slightly from a high pitch, to a lower pitch) Again, these numbers are for the sake of example... the actual change would be much much smaller. A radar can't take a "snapshot" to detect anything. It requires time to work. Radio frequency is quite high, you can receive 100 million wavelengths a second - so from our perspective it seems to work instantly - but it needs to receive the signal for long enough to lock on to the carrier frequency, and then determine small changes in frequency. This is all done with analog electronics because digital computers of today are not powerful enough to make this calculations. Various techniques can be used to assist in making sense of weak signals. One of these is to look for patterns that would represent signals reflecting off of a flat surface that was not at an exact 90 degree angle. These types of analog circuits are commonplace in electronics; but are most commonly implemented in the design of the antenna. The round nature of a balloon is not something most receivers are designed to accomodate (not that it couldn't but it would be a lot of extra unnecessary engineering for most common radar practices). This would explain why an inflated parachute would be more likely to be picked up than a weather balloon. It all comes down to what a particular radar was designed to look for. ATC radar systems may or may not be able to pick up single skydivers. I would be surprised if they did, as they're looking for larger items. They have a larger chance of being able to see a deployed ram-air parachute. The point that I was trying to make is that the air pressure inside of a ram air canopy *would* indirectly make a physical difference in a radar being able to detect that parachute because air is what is giving the parachute a close-to-flat surface, and that most radios are designed to receive signals being sent from (antennas) or reflecting off of (airplanes) relatively flat surfaces. As any radio expert would tell you, what I wrote above isn't 100% accurate from the perspective that I left a lot out about concepts involved in receiving signals... But that was my best job of explaining why the air inside of a ram-air canopy would contribute to the entire parachute becoming easier to see on a radar than if it was not inflated. - without writing a book on radio. While I'm not a professional with radio (I've never made money doing it), about 5 years ago I actually built a radio that I used to measure the distance between the earth and moon by reflecting signals off it. and, It was only a 5 watt transceiver. My original intention was to make a clock that would teach itself what time it was over a few days time based on light changes, and measuring the position and distance of the moon... I only got as far as measuring the distance between the earth and moon before I got bored with the project. Took me about 2 weeks of free time.Matt Christenson [email protected] http://www.RealDropzone.com - A new breed of dropzone manifest software. 1 Quote Share this post Link to post Share on other sites
