Knowledge isn't worth as much as people seem to think; at its heart, it's just trivia. What matters is the ability to think, and that doesn't change from generation to generation.
I agree that the 'ability to think' is the most valuable commodity in this day and age. However, to dismiss 'knowledge' as merely 'trivia' negates the possibility of adding wisdom to decisions and that can be a critical multiplier.
While you may want a dozen different 'artistic interpretations' of what the UI, err "menue's" should look like, for a carrier, that would be a nightmare.
Just imagine being a large carrier's customer care agent, and walking 100 Grandmas a day through how to send a picture to their grand kids... That's why they dictate the UI.
And as for signing apps; that's so the masses don't accidentally go to Jim's Java Joint and download a nefarious application that uploads their entire contact list to the internet, etc, etc....
Actually, it doesn't, it just isn't very clear about it.
The 'gotcha' is the comment "two-thirds of smart phones"; Smart Phones make up a smaller percentage of the global handset population say 10 to 20% globally. The remaining 80 to 90% are regular old phones like the Razor, or Chocolate, Pebl, etc...
Technically each has a different OS, and trying to support every vendor, and each phone model is a nightmare for content developers and providers. You end up with different MIDP support, different screen sizes, and different network access API's. (we won't even bring up Brew vs. Java:-)
I won't argue the points of spectral efficiency with you as you may have a point, and I don't want to do the math at this time of night:-), but I have to take issue with a couple points;
Firstly,
"satellite radio hasn't taken off because the bit rate available results in suboptimal sound quality."
You've got to be kidding? As compared to 'monthly subscription fees' and the need to purchase satellite receivers, you really think sound quality is the deal breaker for the masses??? I would bet that less than 1% of interested consumers even ponder that at the time of purchase... btw & FWIW, I've been a Sirius subscriber for years now, two different cars and three different decks, and in each case the satellite stations sounded much better than regular FM. Not to mention a car is no place for an audiophile...
Secondly;
"It uses an omnidirectional antenna, which means that both Siruis and XM share a 50 MHz band, into which they've crammed three hundred digital radio stations."
Maybe I'm missing a leap of logic here, but an omnidirection antenna has absolutely NOTHING to do with the bandwidth allocation or spectral efficiency in this system... (MiMo and Rec Diversity notwithstanding)
Maybe that just didn't come out the way you meant it too????
I would agree that it seems a little obvious, but have to admit, it's really good work for a student...
The article mentions 4 patents, it would be interesting to know the other three.
I have to hand it to you, that is way more than I would have written this close to Christmas, you must have had all your shopping done!:-)
I'm intrigued by the chart that you link to, as I know a T. Nguyen and am curious if this is some of his handy work from a previous life... One thing that is not obvious from the chart is the distance at which the measurement is made... A -55dBm signal at the center frequency of the C/A GPS band is disconcerting, if made at a standard of 3 meters, but if this is a near field measurement, I'm not so worried.... (btw, I wouldn't call that a stray harmonic, that's broad band noise!)
Perhaps it is just a matter of semantics, but there is no "pulse" involved in the signaling for VOR. It is simply an integration of two signals using FM and AM modulation techniques. To be overly simple about it; with a center freq between 108 and 117.95 MHz, a 30Hz 'reference' signal is FM modulated onto a 9960Hz 'carrier' which is then AM modulated by another 'varying' 30Hz signal. The receiver 'simply' applies a Phase Lock Loop on the 'reference' and compares the 'varying' signal. The difference in phase is indicated as the 'radial' or direction to the VOR station. The 'To' and 'From' indication is derived off of the signals being above or below 180 degrees out of phase.
I think you would agree that good old fashioned FM is fairly immune to transient interference. If not, just kick on your FM radio during your next thunderstorm and see how much static you get around a lightning bolt, then switch over to AM....
Unlike most modern digital radios (WiFi/Cellular) aviation radios still tend to be super heterodyne designs, or at least they where when I stepped out of the business... This gives them much better selectivity, or image rejection, and makes it even harder for transient signal to impact the functionality of the radio.
So, now we have to figure out how to make a cell phone interfere with the VOR... Let's try for a worst case scenario, of the user being seated in the cabin directly above the VOR antenna, or nearest the cabin. Either way, the cell phone would have to create an interfering signal between 108 and 117.95MHz, strong enough to overcome the signal present at the VOR antenna. Since devices run low power 3.3 volt, or lower, logic these days, I think we can safely preclude digital switching noise from the realm of possibility.
As phones go these days that is actually in the realm of the CPU clock frequency. As far as I know, every wireless technology has gone with 'direct conversion' operation these days, so there really is no analog 'mixing' to produce traditional harmonics. Also, all phones have at least a ceramic filter in the front-end, typical is to have the 800MHz and 1900MHz pass bands. Not to mention that the PA and all of the feeding circuits are tuned to those frequencies...
So, we end up needing a device that is significantly malfunctioning, to be putting sufficient power between 108-117.95MHz into a PA that is not designed to transmit there, and we need it to be 'stable' enough to actually interfere with the 'varying' 30Hz signal from the VOR station and not be rejected as random noise.
Obviously, it is within the real of possibility, but certainly at the edges.
However, before we get all worked up about planes falling out of the sky, let's try to keep in mind that people actually flew aircraft before any of these technologies where around. In fact, most pilots I know still look out the window when they fly! The point being, there are well trained crews at the helm of these airships, and should something go awry with their electronics, they are more than capable of dealing with it. Think about it, they can lose the entire navigation rack, ALL of it, and all they need to do is reach down to that air traffic controller and ask for a vector. They still land the plane by looking out the window.
In the end, the only thing I would actually be concerned about is messing with air to ground communication
Well Ceep, you've certainly acquired an impressive amount of anecdotal knowledge on the subject so I'll give you some credit. But I would like to challenge you to explain how, in a commercial aircraft, a 1900MHz or 800MHz, digital mobile phone (i.e. CDMA, GSM, UMTS) would interfere with oh let's say GS, ILS or VOR. Take your pick and engineer away... Preferably with something real, like the IF Frequency of 'X' is jammed by an errant VCO bleeding through the front end of 'Y'... As an EE, you get my drift. The fact is, yes, these error conditions can happen mathematically, but your much, much, much more likely to be affected by natural weather phenomenon, or the guy with the flu that sneezed on your seat during the previous flight segment.:-)
BTW and FWIW; every paper I've seen suggesting reducing the the restrictions on use of PED's suggests allowing the use 'in flight' only, i.e. not during takeoff or approach. So, even if issues were to arise, any aircrew would be able to compensate with no danger to the aircraft.
Two things; Some medical equipment actually reads 'signals' from the body measured in femto amps, so yes, a classic old 800MHz FM cell phone did cause problems...
Regarding your comment on the people 'who DO know', that noticeable absence is probably more to do with a fear of loosing ones job for posting one way or the other. Any company in either industry would be quite upset to see one of their engineers making 'statements' regardless of positive or negative. It's just too much of a liability.
Personally, I've worked in both avionics and wireless design, and I can't wait to have access to my wireless data while in flight. Voice would be OK in a real pinch, but data and SMS would be far more appropriate.
Does anyone happen to have the issue of 'Spectrum' they refer to? It might be a little better than this 'marketing brief' for it...
Note that it says "These devices CAN disrupt normal operation....", it does not say "DID" or "HAVE", or even 'we witnessed'.
There are a lot of things that 'can' happen in the physical realm, but it doesn't mean they are going to...
I'd be more concerned about someone firing a frozen chicken at the plane while on approach:-)
You need to go back and watch that episode again. I've worked in both avionics, and the wireless industry, so I recorded it and have watched it several times just for laughs.
The situation you are referring to was TOTALLY bogus. Instruments out of the rack, no shielding for the wiring, etc... You can't get much further from a real aircraft installation. (btw, it was a GSM handset, and I think they were testing at 800MHz)
Additionally, when they did try a real aircraft, there was absolutely no effect from the cell phone.
Given the frequency domain differences, cable shielding, and spatial diversity in an aircraft makes the amount of energy from your cell phone the equivalent of 'a bug on the windshield'.
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Knowledge isn't worth as much as people seem to think; at its heart, it's just trivia. What matters is the ability to think, and that doesn't change from generation to generation.
I agree that the 'ability to think' is the most valuable commodity in this day and age. However, to dismiss 'knowledge' as merely 'trivia' negates the possibility of adding wisdom to decisions and that can be a critical multiplier.
While you may want a dozen different 'artistic interpretations' of what the UI, err "menue's" should look like, for a carrier, that would be a nightmare.
Just imagine being a large carrier's customer care agent, and walking 100 Grandmas a day through how to send a picture to their grand kids... That's why they dictate the UI.
And as for signing apps; that's so the masses don't accidentally go to Jim's Java Joint and download a nefarious application that uploads their entire contact list to the internet, etc, etc....
Actually, it doesn't, it just isn't very clear about it.
:-)
The 'gotcha' is the comment "two-thirds of smart phones"; Smart Phones make up a smaller percentage of the global handset population say 10 to 20% globally. The remaining 80 to 90% are regular old phones like the Razor, or Chocolate, Pebl, etc...
Technically each has a different OS, and trying to support every vendor, and each phone model is a nightmare for content developers and providers. You end up with different MIDP support, different screen sizes, and different network access API's. (we won't even bring up Brew vs. Java
I won't argue the points of spectral efficiency with you as you may have a point, and I don't want to do the math at this time of night :-), but I have to take issue with a couple points;
Firstly, "satellite radio hasn't taken off because the bit rate available results in suboptimal sound quality."
You've got to be kidding? As compared to 'monthly subscription fees' and the need to purchase satellite receivers, you really think sound quality is the deal breaker for the masses??? I would bet that less than 1% of interested consumers even ponder that at the time of purchase... btw & FWIW, I've been a Sirius subscriber for years now, two different cars and three different decks, and in each case the satellite stations sounded much better than regular FM. Not to mention a car is no place for an audiophile...
Secondly; "It uses an omnidirectional antenna, which means that both Siruis and XM share a 50 MHz band, into which they've crammed three hundred digital radio stations."
Maybe I'm missing a leap of logic here, but an omnidirection antenna has absolutely NOTHING to do with the bandwidth allocation or spectral efficiency in this system... (MiMo and Rec Diversity notwithstanding) Maybe that just didn't come out the way you meant it too????
I would agree that it seems a little obvious, but have to admit, it's really good work for a student... The article mentions 4 patents, it would be interesting to know the other three.
I have to hand it to you, that is way more than I would have written this close to Christmas, you must have had all your shopping done! :-)
I'm intrigued by the chart that you link to, as I know a T. Nguyen and am curious if this is some of his handy work from a previous life... One thing that is not obvious from the chart is the distance at which the measurement is made... A -55dBm signal at the center frequency of the C/A GPS band is disconcerting, if made at a standard of 3 meters, but if this is a near field measurement, I'm not so worried.... (btw, I wouldn't call that a stray harmonic, that's broad band noise!)
Perhaps it is just a matter of semantics, but there is no "pulse" involved in the signaling for VOR. It is simply an integration of two signals using FM and AM modulation techniques. To be overly simple about it; with a center freq between 108 and 117.95 MHz, a 30Hz 'reference' signal is FM modulated onto a 9960Hz 'carrier' which is then AM modulated by another 'varying' 30Hz signal. The receiver 'simply' applies a Phase Lock Loop on the 'reference' and compares the 'varying' signal. The difference in phase is indicated as the 'radial' or direction to the VOR station. The 'To' and 'From' indication is derived off of the signals being above or below 180 degrees out of phase.
I think you would agree that good old fashioned FM is fairly immune to transient interference. If not, just kick on your FM radio during your next thunderstorm and see how much static you get around a lightning bolt, then switch over to AM....
Unlike most modern digital radios (WiFi/Cellular) aviation radios still tend to be super heterodyne designs, or at least they where when I stepped out of the business... This gives them much better selectivity, or image rejection, and makes it even harder for transient signal to impact the functionality of the radio.
So, now we have to figure out how to make a cell phone interfere with the VOR... Let's try for a worst case scenario, of the user being seated in the cabin directly above the VOR antenna, or nearest the cabin. Either way, the cell phone would have to create an interfering signal between 108 and 117.95MHz, strong enough to overcome the signal present at the VOR antenna. Since devices run low power 3.3 volt, or lower, logic these days, I think we can safely preclude digital switching noise from the realm of possibility.
As phones go these days that is actually in the realm of the CPU clock frequency. As far as I know, every wireless technology has gone with 'direct conversion' operation these days, so there really is no analog 'mixing' to produce traditional harmonics. Also, all phones have at least a ceramic filter in the front-end, typical is to have the 800MHz and 1900MHz pass bands. Not to mention that the PA and all of the feeding circuits are tuned to those frequencies...
So, we end up needing a device that is significantly malfunctioning, to be putting sufficient power between 108-117.95MHz into a PA that is not designed to transmit there, and we need it to be 'stable' enough to actually interfere with the 'varying' 30Hz signal from the VOR station and not be rejected as random noise.
Obviously, it is within the real of possibility, but certainly at the edges.
However, before we get all worked up about planes falling out of the sky, let's try to keep in mind that people actually flew aircraft before any of these technologies where around. In fact, most pilots I know still look out the window when they fly! The point being, there are well trained crews at the helm of these airships, and should something go awry with their electronics, they are more than capable of dealing with it. Think about it, they can lose the entire navigation rack, ALL of it, and all they need to do is reach down to that air traffic controller and ask for a vector. They still land the plane by looking out the window.
In the end, the only thing I would actually be concerned about is messing with air to ground communication
Well Ceep, you've certainly acquired an impressive amount of anecdotal knowledge on the subject so I'll give you some credit. But I would like to challenge you to explain how, in a commercial aircraft, a 1900MHz or 800MHz, digital mobile phone (i.e. CDMA, GSM, UMTS) would interfere with oh let's say GS, ILS or VOR. Take your pick and engineer away... Preferably with something real, like the IF Frequency of 'X' is jammed by an errant VCO bleeding through the front end of 'Y'... As an EE, you get my drift. The fact is, yes, these error conditions can happen mathematically, but your much, much, much more likely to be affected by natural weather phenomenon, or the guy with the flu that sneezed on your seat during the previous flight segment. :-)
BTW and FWIW; every paper I've seen suggesting reducing the the restrictions on use of PED's suggests allowing the use 'in flight' only, i.e. not during takeoff or approach. So, even if issues were to arise, any aircrew would be able to compensate with no danger to the aircraft.
Can you throw a reference for that event? Accident report, etc...??? Thanks!
Two things; Some medical equipment actually reads 'signals' from the body measured in femto amps, so yes, a classic old 800MHz FM cell phone did cause problems... Regarding your comment on the people 'who DO know', that noticeable absence is probably more to do with a fear of loosing ones job for posting one way or the other. Any company in either industry would be quite upset to see one of their engineers making 'statements' regardless of positive or negative. It's just too much of a liability. Personally, I've worked in both avionics and wireless design, and I can't wait to have access to my wireless data while in flight. Voice would be OK in a real pinch, but data and SMS would be far more appropriate.
Does anyone happen to have the issue of 'Spectrum' they refer to? It might be a little better than this 'marketing brief' for it... Note that it says "These devices CAN disrupt normal operation....", it does not say "DID" or "HAVE", or even 'we witnessed'. There are a lot of things that 'can' happen in the physical realm, but it doesn't mean they are going to... I'd be more concerned about someone firing a frozen chicken at the plane while on approach :-)
You need to go back and watch that episode again. I've worked in both avionics, and the wireless industry, so I recorded it and have watched it several times just for laughs. The situation you are referring to was TOTALLY bogus. Instruments out of the rack, no shielding for the wiring, etc... You can't get much further from a real aircraft installation. (btw, it was a GSM handset, and I think they were testing at 800MHz) Additionally, when they did try a real aircraft, there was absolutely no effect from the cell phone. Given the frequency domain differences, cable shielding, and spatial diversity in an aircraft makes the amount of energy from your cell phone the equivalent of 'a bug on the windshield'.