The short answer is it not usually but it depends.
There are specific circumstances under which a pilot is required to file a flight plan. For the short hop in good weather, it's not likely to be required. Departing or arriving at a busy airport may require a clearance (permission and specific instructions) from ATC but not necessarily a flight plan.
It's an airplane when in the air or taxiing at an airport, private or public. The FAA already has rules covering certificated aircraft and pilots.
Samba 3.0 (release) is in the cooker contribs with package names samba3*. I'm running it now at work. It's packaged to be installed (but not ran) simultaneously with Samba 2.x, using a 3 suffix for all conflicting files and directory names.
Haven't seen the 9.2 release contribs though - has anyone? At least a Samba 3.0 RC should be in there, if not the release.
The author and I worked together in 1997, just as he was starting to transition from 900 MHz to 2.4 GHz equipment. At the time he was seeing some pretty serious interference problems with 900 MHz in the south SF bay - presumably due to the boom in 900 MHz cordless phones. Rest assured he has a lot of experience with that band, so I don't know why he wouldn't write about it, unless he doesn't consider it viable for modern installations.
One interesting thing about 900 MHz is that although the free air path loss and absorption by vegetation is indeed lower vs. higher frequencies, it's also more difficult to deploy antennas with gains like you find in the 2.4 and 5.7 GHz bands. I'm talking mostly about point-to-point deployments. In designs I've done, the system loss (calculation of amount of energy arriving at the remote receiver), assuming antennas of reasonable size, was almost the same for 900 or 2.4. One significant advantage of 2.4 is an 83 MHz band to play with vs. a 26 MHz band on 900. I wouldn't say that kind of equivalence applies to 5.7 though, due to the environmentally-related fade factors starting to really kick in.
I have a lot of respect for Jack and his commitment to wireless, and hope his book sells a gazillion copies. He's a fellow ham radio operator and knows the RF side far better than most wireless LAN/WAN people I've met.
As some other posters have posited, the more modern airliners have extensive shielding and *shouldn't* show much susceptability to RF interference. I agree with you, it's SNR degradation that poses the greatest threat. Not to say it cannot happen, though. I fly light GA aircraft, which are not that well built. A front seat passenger is also just a couple feet away from critical instruments.
Some time ago I came across a database the FAA keeps, where pilots can anonymously report safety-related incidents. There I read many documented and recent cases of erroneous nav instrument readings eventually traced back to a passenger electronic device. Many were airliners. I was shocked (no pun intended).
Just this past week I rented an older plane and once in the air, found one of its instruments was malfunctioning and interfering with another's operation in a complicated way, depending on what frequency the interfering instrument (a receiver!) was set to. Yes, the needle *was* blipping. (It was a VOR receiver.) It partially desensed the working instrument's receiver when set on particular frequencies - exactly the phenomenon you mentioned. I figured it out in a couple minutes, and at the beginning of the trip, so I was not uncertain of my course for long. Fortunately that flight was being made under VFR, or else I would have had to immediately report the failure to ATC (rules again).
My instructor is less conservative than I am. I just happen to also have experience with RF - particularly VHF - and RF testing leading to certification of part 15 intentional radiators. *Most* electronic devices emit quite a lot of 'crud'. I've seen it first hand in the lab.
The safety bar for aviation is quite a bit higher than some might think is necessary. Over time I've come to believe many FAA regulations were made reactively, i.e., something bad happened, it was investigated, the cause found, and a regulation was made. It's not paranoia, but just an awareness of what's really at stake. A quick pull over to the side of the road is not an option when in the air.
The most dangerous kind of equipment/instrument failure in IFR flight is one where the instrument appears to be working normally, but is in fact giving an erroneous reading. I have no intention of knowingly putting myself and my passengers at risk, let alone violate FAA regulations. Over time I certainly may relax a bit on this if I deem the risk acceptable and it does not blow any regulation.
What, don't you think RF engineers apply basic engineering principles? An RF engineer who doesn't won't stay employed for long.
Physical proximity is everything for RF. A 600 mW cell phone transmitter 20-30 ft. away from a navigational instrument is a real potential problem. More so than a 50 kW FM transmitter on a tower a mile or two away. Do the math, taking note of the 1/r^2 factor in the field strength calculation.
There are also *plenty* of documented cases where some gadget or another has interfered with aircraft navigational systems. It's the unintentional and unpredictable radiation that is a problem. Actual radio receivers are usually right out because they also tend to have oscillators nearby the VHF and UHF frequencies used for the aircraft's nav equipment. The equipment approved for on-board use, e.g., the 'airfone' units, have been tested and shown not to interfere; they are predictable. Not so for items brought on by passengers.
For good reason, the FAA regulations prohibit 'portable electronic devices' being operated while an aircraft flies under IFR. I believe that's relaxed somewhat for commercial airline operations above 10,000 ft. I am also a certificated pilot training for my instrument rating, and you can bet I am not going to allow my future passenger(s) to run their CD walkmans while making my way through a cloud deck under IFR - legal or not.
You're right about the hams but practically speaking, it's little or nothing to worry about.
Hams are growingly concerned about their spectrum getting usurped (and rightfully so, it has happened before and the ARRL is constantly fending off new threats). Part of that sentiment has an outlet via reminders to spectrum users lower on the 'totem pole' that hams have higher status.
IIRC, the 2.4 GHz ham band extends from 2390 to 2450 MHz. (They used to have 2300-2310 or so too, but it's gone.) However, the FCC Part 15-247 unlicensed band extends from 2400 to 2483.5 MHz. This means that the upper 5 or so 802.11b channels are out of the way of hams that might be operating in their licensed band. High power ham radios in that 2390-2450 slot *shouldn't* be emitting much energy outside it, but even a little can cause interference to 802.11b radios operating above 2450. Summary: almost half the unlicensed 2.4 band the hams cannot touch but that doesn't mean there would be no problems.
There are also strict rules on how hams can use their spectrum. A *LOT* of what unlicensed users can do in the way of data transfer (almost anything goes) is prohibited for hams. Anything that facilitates a business is out. Another big one is the issue of unlicensed operators causing emissions of a ham radio (they basically cannot). The regs are a bit vague but that's the gist of it. The result is that the only legally 'safe' manner in which to operate is to talk only to other hams over such a licensed link.
I am a licensed ham - have been since I was 9 years old, yet feel sad when I read the article. It used to be hams were on the forefront of developing new radio technologies (indeed, that's one of the tenets of the amateur radio charter - furtherance of the radio art) but here I see them (us) glomming onto technology mostly developed in the commercial sector, and threatening to push unlicensed users out. Hams still have a boatload of frequencies available, especially in the microwave regions. However, most of us don't want to take the time to design new radios. You get the picture.
Even though I could legally use an 802.11b radio at high power, etc., I'd rather operate unlicensed and not be subject to restrictions on what traffic passes over a link. My Internet connection at home is via an 802.11b-based provider.
Those aren't the fans, but the movable control surfaces (giving specific direction to the downward thrust from the fans). The actual fans are just above them, and are not visible.
If the design goal is highest efficiency for low frequency reproduction (and it usually is), it's difficult or impossible to beat a big driver, mostly for that long throw ability and cone area to push the air.
That said, small drivers can also be made with relatively long throws and a bunch of them can move a surprising amount of air. A benefit of the many-small-drivers approach is they can also handle mid and some high frequencies.
And this is where the need for aggressive EQ comes in. An array of long-throw, wide range 4" drivers together can respond on the lows but they'll be too strong on the mid and highs unless the EQ curve compensates for that.
I'd say this proposed setup from Pioneer is an example of a system that gives up that highest low-frequency efficiency for flexibility - ability to (more) precisely image sound. Now made possible with computer controls inexpensive enough to go into a consumer product.
Funny that it's 254 speakers (2^8 minus 2) but I digress...
Why *can't* a bunch of little speakers reproduce low frequencies? The famous Bose 901 contained what, 16 or so 4" speakers per enclosure? (required active equalization but it sounded pretty good).
AFAIK, it's just a matter of moving enough air, whether by a few woofers or a lot of smaller speakers.
Add some fine-grained control as to exactly what signal goes to each speaker, and the result could be seriously cool...
disclaimer: I don't work for Pioneer or have any particular affinity for their products.
Slashdot Mirror
The short answer is it not usually but it depends.
There are specific circumstances under which a pilot is required to file a flight plan. For the short hop in good weather, it's not likely to be required. Departing or arriving at a busy airport may require a clearance (permission and specific instructions) from ATC but not necessarily a flight plan.
It's an airplane when in the air or taxiing at an airport, private or public. The FAA already has rules covering certificated aircraft and pilots.
yes, IAAP (I am a pilot).
The prepended "1" is the country code for the US. Seems many other countries have two or three digit codes.
Silly to have to dial it within the country though...
Samba 3.0 (release) is in the cooker contribs with package names samba3*. I'm running it now at work. It's packaged to be installed (but not ran) simultaneously with Samba 2.x, using a 3 suffix for all conflicting files and directory names.
Haven't seen the 9.2 release contribs though - has anyone? At least a Samba 3.0 RC should be in there, if not the release.
Well, OpenOffice.org is in fact the product name too.
It's one way to get the web site name out there...
The author and I worked together in 1997, just as he was starting to transition from 900 MHz to 2.4 GHz equipment. At the time he was seeing some pretty serious interference problems with 900 MHz in the south SF bay - presumably due to the boom in 900 MHz cordless phones. Rest assured he has a lot of experience with that band, so I don't know why he wouldn't write about it, unless he doesn't consider it viable for modern installations.
One interesting thing about 900 MHz is that although the free air path loss and absorption by vegetation is indeed lower vs. higher frequencies, it's also more difficult to deploy antennas with gains like you find in the 2.4 and 5.7 GHz bands. I'm talking mostly about point-to-point deployments. In designs I've done, the system loss (calculation of amount of energy arriving at the remote receiver), assuming antennas of reasonable size, was almost the same for 900 or 2.4. One significant advantage of 2.4 is an 83 MHz band to play with vs. a 26 MHz band on 900. I wouldn't say that kind of equivalence applies to 5.7 though, due to the environmentally-related fade factors starting to really kick in.
I have a lot of respect for Jack and his commitment to wireless, and hope his book sells a gazillion copies. He's a fellow ham radio operator and knows the RF side far better than most wireless LAN/WAN people I've met.
As some other posters have posited, the more modern airliners have extensive shielding and *shouldn't* show much susceptability to RF interference. I agree with you, it's SNR degradation that poses the greatest threat. Not to say it cannot happen, though. I fly light GA aircraft, which are not that well built. A front seat passenger is also just a couple feet away from critical instruments.
Some time ago I came across a database the FAA keeps, where pilots can anonymously report safety-related incidents. There I read many documented and recent cases of erroneous nav instrument readings eventually traced back to a passenger electronic device. Many were airliners. I was shocked (no pun intended).
Just this past week I rented an older plane and once in the air, found one of its instruments was malfunctioning and interfering with another's operation in a complicated way, depending on what frequency the interfering instrument (a receiver!) was set to. Yes, the needle *was* blipping. (It was a VOR receiver.) It partially desensed the working instrument's receiver when set on particular frequencies - exactly the phenomenon you mentioned. I figured it out in a couple minutes, and at the beginning of the trip, so I was not uncertain of my course for long. Fortunately that flight was being made under VFR, or else I would have had to immediately report the failure to ATC (rules again).
My instructor is less conservative than I am. I just happen to also have experience with RF - particularly VHF - and RF testing leading to certification of part 15 intentional radiators. *Most* electronic devices emit quite a lot of 'crud'. I've seen it first hand in the lab.
The safety bar for aviation is quite a bit higher than some might think is necessary. Over time I've come to believe many FAA regulations were made reactively, i.e., something bad happened, it was investigated, the cause found, and a regulation was made. It's not paranoia, but just an awareness of what's really at stake. A quick pull over to the side of the road is not an option when in the air.
The most dangerous kind of equipment/instrument failure in IFR flight is one where the instrument appears to be working normally, but is in fact giving an erroneous reading. I have no intention of knowingly putting myself and my passengers at risk, let alone violate FAA regulations. Over time I certainly may relax a bit on this if I deem the risk acceptable and it does not blow any regulation.
What, don't you think RF engineers apply basic engineering principles? An RF engineer who doesn't won't stay employed for long.
Physical proximity is everything for RF. A 600 mW cell phone transmitter 20-30 ft. away from a navigational instrument is a real potential problem. More so than a 50 kW FM transmitter on a tower a mile or two away. Do the math, taking note of the 1/r^2 factor in the field strength calculation.
There are also *plenty* of documented cases where some gadget or another has interfered with aircraft navigational systems. It's the unintentional and unpredictable radiation that is a problem. Actual radio receivers are usually right out because they also tend to have oscillators nearby the VHF and UHF frequencies used for the aircraft's nav equipment. The equipment approved for on-board use, e.g., the 'airfone' units, have been tested and shown not to interfere; they are predictable. Not so for items brought on by passengers.
For good reason, the FAA regulations prohibit 'portable electronic devices' being operated while an aircraft flies under IFR. I believe that's relaxed somewhat for commercial airline operations above 10,000 ft. I am also a certificated pilot training for my instrument rating, and you can bet I am not going to allow my future passenger(s) to run their CD walkmans while making my way through a cloud deck under IFR - legal or not.
You're right about the hams but practically speaking, it's little or nothing to worry about.
Hams are growingly concerned about their spectrum getting usurped (and rightfully so, it has happened before and the ARRL is constantly fending off new threats). Part of that sentiment has an outlet via reminders to spectrum users lower on the 'totem pole' that hams have higher status.
IIRC, the 2.4 GHz ham band extends from 2390 to 2450 MHz. (They used to have 2300-2310 or so too, but it's gone.) However, the FCC Part 15-247 unlicensed band extends from 2400 to 2483.5 MHz. This means that the upper 5 or so 802.11b channels are out of the way of hams that might be operating in their licensed band. High power ham radios in that 2390-2450 slot *shouldn't* be emitting much energy outside it, but even a little can cause interference to 802.11b radios operating above 2450. Summary: almost half the unlicensed 2.4 band the hams cannot touch but that doesn't mean there would be no problems.
There are also strict rules on how hams can use their spectrum. A *LOT* of what unlicensed users can do in the way of data transfer (almost anything goes) is prohibited for hams. Anything that facilitates a business is out. Another big one is the issue of unlicensed operators causing emissions of a ham radio (they basically cannot). The regs are a bit vague but that's the gist of it. The result is that the only legally 'safe' manner in which to operate is to talk only to other hams over such a licensed link.
I am a licensed ham - have been since I was 9 years old, yet feel sad when I read the article. It used to be hams were on the forefront of developing new radio technologies (indeed, that's one of the tenets of the amateur radio charter - furtherance of the radio art) but here I see them (us) glomming onto technology mostly developed in the commercial sector, and threatening to push unlicensed users out. Hams still have a boatload of frequencies available, especially in the microwave regions. However, most of us don't want to take the time to design new radios. You get the picture.
Even though I could legally use an 802.11b radio at high power, etc., I'd rather operate unlicensed and not be subject to restrictions on what traffic passes over a link. My Internet connection at home is via an 802.11b-based provider.
'nuff said.
Those aren't the fans, but the movable control surfaces (giving specific direction to the downward thrust from the fans). The actual fans are just above them, and are not visible.
If the design goal is highest efficiency for low frequency reproduction (and it usually is), it's difficult or impossible to beat a big driver, mostly for that long throw ability and cone area to push the air.
That said, small drivers can also be made with relatively long throws and a bunch of them can move a surprising amount of air. A benefit of the many-small-drivers approach is they can also handle mid and some high frequencies.
And this is where the need for aggressive EQ comes in. An array of long-throw, wide range 4" drivers together can respond on the lows but they'll be too strong on the mid and highs unless the EQ curve compensates for that.
I'd say this proposed setup from Pioneer is an example of a system that gives up that highest low-frequency efficiency for flexibility - ability to (more) precisely image sound. Now made possible with computer controls inexpensive enough to go into a consumer product.
Funny that it's 254 speakers (2^8 minus 2) but I digress...
Why *can't* a bunch of little speakers reproduce low frequencies? The famous Bose 901 contained what, 16 or so 4" speakers per enclosure? (required active equalization but it sounded pretty good).
AFAIK, it's just a matter of moving enough air, whether by a few woofers or a lot of smaller speakers.
Add some fine-grained control as to exactly what signal goes to each speaker, and the result could be seriously cool...
disclaimer: I don't work for Pioneer or have any particular affinity for their products.
about 1KW (1000W) per square meter