A lot of places in this world don't have computers, and those people survive just fine.
Very true, but did those places gradually move their way of being towards electrified industry to the point of completely relying on it and then... have those mechanisms of survival suddenly stop working?
I think it would have little effect on most electronics. Perhaps it could even be a positive effect.
I would like to think that security considerations in antenna design should be absolutely minimal. To the point where the only consideration might be for a design on both ends that allows very high rejection of signals that don't come from the intended direction. To avoid any low tech denial of service attacks. Of course, this can be achieved with moderate effort placing transmitters within the line of sight to disrupt the link with an appropriately chosen modulation method perhaps injecting noise, at a power greater than the victim radio links. I say "moderate effort" because this is childs play compared to defeating high strength encryption and authentication methods. Hell, you could even just disrupt the link with some metallic obstacle.
A place I worked at had irregular drop-outs on the inter office microwave which was puzzling. The techs got up onto the roof and saw off in the distance some construction work being done with a crane which was occasionally blocking the line of sight as it moved about. : )
Any radio link should be considered insecure as far as eavesdropping and interception goes, if it does not employ encryption and authentication. But this has nothing to do with antenna design.
An antenna "system" that dynamically configures itself for multiple beams could maybe be coaxed into using up all it's beams into one area, as a denial of service attack. But I think guarding against such a thing could be trivial. All that would be needed is some consistency checking that assures that no channels of the same frequency overlap in the radiation pattern, which could effectively limit a DoS.
Don't worry, I won't yell and I won't say you are wrong either. Because what different people consider `active' can be very different things.
I have a chuckle when I hear people in the mountain bike world call their rear suspension systems `active'. I can't help but to think that something that is active, is something that provides certain gains that are "paid for" through external power, whereas a passive device is merely something that passes gains on through efficient designs that merely convert or transfer the power that they receive.
It's a grey area, but as far as I am concerned, a passive antenna includes no powered circuitry to enhance it's performance.
As far as I am concerned, as a purist, an antenna that includes a low noise amp, is a passive antenna with an active assistance device bolted on.
People choose to refer to these as "active antennas" to make them easier to describe, so I can't complain too much about that. As long as I know. : )
Second, the article mentions it uses a gigabit connection. Umm...why?
Because having an antenna design/phase manipulation system such as this sharing it's entire range with just 11Mbit/sec would be a complete waste of the system itself.
They must be using multiple channels to better use the bandwidth capabilities of this antenna.
The most amazing part of this will not be if they can actually produce an antenna that comes close to what they are claming
Phased arrays that use manipulated phases to manipulate radiation pattern are not new. They're actually pretty old. I wouldn't be amazed to see them do it.
Using them for domestic use is new though and I'm glad to see it coming.
I see how the directional antenna on the base station can transmit to the roaming laptop that is far away. But, the roaming laptop has a standard internal omnidirectional antenna, how does it transmit back?
Good question, here's the answer: Antenna gain works for the transmitted signal AND the received sensitivity.
Meaning that the directional antenna is not only able to get the transmitted signal to go a long way through a higher effective radiated power by focusing the power in one direction, but it is also able to boost the signal it receives through higher sensitivity through also the same focusing in that same direction. These go hand in hand.
This is in stark contrast to merely using a higher output transmitter in only one radio, which can have the effect of elimination of duplex operation.
When doing 802.11b over long distances, the directional antenna is needed on BOTH sides.
No, wait a sec, keep your mind open. This is not the case. Directional antenna's on both ends will allow greater distances and bandwidth, but if the combined antenna gains, transmitter power, receiver sensitivity, transmission line losses (radio to antenna cabling) and atmospheric conditions allow communications over a certain distance, then the actual antenna radiation pattern (omni vs directional, assuming directional pattern is used to the fullest potential for the claimed gain) will be of no consequence. From strictly an antenna design point of view, the gain is what matters for a given distance to be feasible, not the pattern. But it just so happens that an antenna that provides a narrow beam also can provide a high gain, but that's not to say that this is always a requirement.
An omni direction antenna, being used for point to point is merely wasting the majority of it's output power and not receiving as much remote signal as it could if it were directional. This does not mean it will not work.
Case in point, cell phones: Base stations use directional antennas pointing in different directions (I usually see towers pointing in what looks like 3 separate directions with vertically stacked phased arrays), yet your phone uses an omni directional antenna simply because you the user, can not be expected to point it accurately each time and for the duration of a phone call. Yet, the system works well, because the directional antennas at the base stations make up for the inefficient omni design of your phone with their own high gains in both transmitted power and received signal.
Although years ago there was a Motorola analog mobile phone which actually had an automatically tracking phased array (just two verticals) which the phone would manipulate to track the current base station so as to allow the best reception. I believe this phone never made it to market because one of the techs testing the phone got a cancer near his temple on the side he used the phone and thus the phone got bad publicity.
1> The math behind antenna design theory leaves little room for innovation.
Well, except for the fact that the best antenna designers DON'T UNDERSTAND the complete math behind antenna design theories!
Last time I checked (9 years ago), the formulas for the Yagi directional antenna designs were approximate to the point of requiring trial and error manual tweaking to get best performance, due to the fact that the exact formulas have yet to be found. We have something really close, but we didn't know it all. It was commonly believed however, that the US Navy did in fact know the exact formula, but are keeping it secret.
I don't see where this antenna design is any more efficient than many that are already on the market..
This design dynamically manipulates the phasing of the hundreds of antenna's that comprise the phased array, so that multiple beams can be made, independently directed and track targets without any physical antenna movement.
See the difference in this antenna now? It's not a new concept, but certainly a new concept for WiFi.
2> There are already products on the market that can push WiFi signals well over 4 miles.
Whoa! Now back up a second there cowboy, did you say FOUR MILES! WHOA!
4 miles is nuttin'. I've seen 30km and heard reports of 30 miles.
They might as well be putting out a press release saying they've invented a circular device that they're calling a "wheel".
In the past, I've been guilty of not reading the article. Guess what...
WaveRider Communications [waverider.com] has been selling 802.11 based units with ranges up to 15 km (with outdoor antennas) for several years.
And can this WaveRider unit have a radiation pattern that suddenly changes from 98% at 0 degrees, to 49% 0 degrees and 49% 37 degrees at a moving target which it tracks without any physical antenna movement?
There is the magic and there is the cost. Though it's not really magic, just looks like it, especially when it can be a lot more than just 2 targets.
Yeah, yeah -- they tried to sell me that for my cellphone too. Doesn't work.:)
This is not some silly snake-oil sticker. This is the commercial application of an old technology that has been waiting for one side of it's technology to catch up (although military, etc have used it for many years).
Computing power meets manipulated phased arrays!
PS, they do work, extremely well. So well in fact, that some people will see their claims as snake-oil!
Look into the REAL technology before passing it by.
But most importantly, having hundreds of phased antennas allows multiple separate beams in addition to dynamic changes to (not just the direction but) the overall radiation pattern.
No, this is not new, it's old by military standards, but pretty nifty to see on the domestic market and a really neat application of technology.
They switched it to horizontal polariztion and now we get a good 1.2Mbit+ connection at our site in the middle of nowhere.
Are your techs routing your PABX lines through it also? You can get about 18 (uncompressed) 64k voice lines across that.
The PABX could most likely be set up to first try to route internal calls (and maybe least cost routed external calls) through that link with telco lines as the fail-over to save some money.
Compress those voice channels and get much more.
I worked for a place that had a set up like this at a backup site that housed system developers and entire backup production systems. Pick up a phone and call an extension at the remote site and the call would go through the microwave without the user ever knowing the difference. If the microwave was saturated including the reserved bandwidth for the PABX, then telco lines would be used (a rarity), also without the phone user ever noticing a thing.
I know of an airline company in Sydney that installed a microwave link between the city office and Sydney airport. They routed their internal inter-office calls through it and in the first year, the money they saved from reduced telco bills actually payed for the system and then some.
Mention it to your boss if it isn't being done, its a very worthwhile exercise.
I've never seen any published studies that show this.
Agreed wholeheartedly occamboy. There have been absolutely tons of studies showing overwhelming evidence that ionizing radiation causes cancers and yet tons of studies that failed to show any evidence that non-ionizing radiation (microwaves, mobile phones, WiFi, etc) even slightly highten cancer incidents.
I take that as pretty overwhelming evidence that there is little to no risk with these devices.
Besides that, more effective use of effective radiated power can only serve to reduce overall radiated power.
This technology is older than I am and probably older than most of you too. : )
I have an old FORTRAN text book that has a programming case study about FORTRAN code running on old VAXen being used in RADAR and communications surveillance for the USAF.
The picture in the case study depicts (what is obvious to me as an ex RADAR tech), a few groups of typical RADAR frequency phased arrays.
Back then (late 80's) the technologies I witnessed were amazing, and I have a little chuckle when I see whittled down versions of these various technologies in domestic equipment 20 years later. ; )
I wouldn't get too excited everytime a company comes out with some wireless gadget without documented proof that they actualy made it secure for the user to use.
If you need your wireless network security to be provided by the antenna, you have very serious security problems.
Oh, so now wardrivers can be 2-3 streets away to hack into the network instead of right next to the house? Wonderful.
Hackers have been hacking from streets away long before this came out. Good old high gain antenna designs would allow this with searching done with antenna direction changes as opposed to antenna location changes that driving around facilitates. This new product might just make it quicker and easier to find victim networks.:)
But never fear, you have a life and a place in the World right?
People here who usually get in quick often tend to have little valuable to say, since they spend their lives refreshing/. in the hopes that they can say something vaguely disguised as interesting, informative or insightful to get moderated up before real people with real knowledge who only get to check/. once a day (because they're actually interested in the stories) take their points.
The problem is that they are usually quite expensive, take up a lot of space, AND usually require considerable processing
Phased array antenna's don't require any processing at all.
The application of automatic manipulation of the individual phases (in particular designs that allow it), to give dynamic patterns that change with detected requirements, is something that requires considerable processing power.
Consider it a sort of software antenna, you have a series of antenna that you can bias towards a particular direction. You then listen for incoming signals and use a processor to calculate environmental multipath (RF signals bouncing off buildings, etc.) and then fire off your signal so that the main signal and multipath reflections arrive at the reciever at the same time. Instant gain.
This is not a description of a "phased array" antenna design, this is a description of an application of a particular phased array design.
Not all phased array designs allow simple pattern changes based on phase manipulation.
Some can have none, requiring physical antenna pointing, some have simple switched 90 degree changes (forward+back/left+right vertical designs) and then others can be super advanced and highly variable of the likes of military designs with all sorts in between.
BTW, something I really hate about/., is that when I see stuff like this, I feel very compelled to post, rather than moderate (even if I did have moderator points right now).
I imagine this is a feeling most others share, which leads me to the logical and very sad conclusion, moderators are usually ignorant about what they moderate, plain and simple.
Which is why complete crap often gets moderated up and PhD's often get moderated down.
Think of how FM broadcasters get increased erp and still have a circular coverage area.
This is absolutely correct, but does not argue in any way the comment that this reduces the uniform coverage.
You can bias towards distance and not narrow the beam width.
If you compare the two designs you are referring to, but only look at vertical pattern at any one particular horizontal angle, you will actually find, that the virtual "beam" IS in fact narrowed vertically and thus the gain is made possible. Just because it is narrowed toward human population does not make his comments about loss of uniform coverage less true.
We should not delve too far into practicalities and at the same time move away from the technicalities, because we gain the practicalities from the technicalities.
I've been invloved in phased array antenna design and military RADAR since the late 80's. The above comment is NOT Score:5 Informative!
1. "phased array antenna" DOES NOT EQUAL "active antenna". A phased array can receive benefits from active circuitry just the same way a simple single vertically polarized "whip" can.
2. "Your statements are true for a passive antenna design." This statement... "You can get more distance in exchange for not getting uniform coverage." is true for any particular moment in time, for EVERY antenna design, bar none. And the whole paragraph of draziw's post stands out glaringly to me, that he knows antenna design practicalities.
Antenna gain depends completely on how well the antenna is tuned for the intended frequency and the radiation/sensitivity pattern it creates.
If you want signals to travel VERY far for example, you could design an antenna that (in laymens terms) compresses it's transmitted power (as in Effective Radiated Power) to a beam, or from a receiver point of view focuses in one particular direction. What this also does, is effectively quieten/deafen the antenna to areas other than that direction intended to communicate with. Thus, his comment about loss of uniform coverage.
Now before anyone argues the virtues of active designs, they MUST consider that the circuitry added to "active antennas" (usually wide-band receiver amplification) does NOT constitute and nor should it, an antenna at all! This is merely a traditional antenna, with active radio amplification which serves to feed ANOTHER radio and APPEARS to be a very effective antenna.
In short, technically, there is no such thing as an "active antenna".
I've been designing my own WiFi massive phased array, a-la flat jet fighter RADAR arrays. I'm currently trying to figure out whether just building a good parabolic design would be easier as the many highly tuned and quite small dipoles would be hard to tune and assemble in phase well enough.
I'll venture it'll cost about $800
I'll venture you don't fully know, that which you speak. I am really starting to hate/. Someone posts a comment here that is absolute textbook and then some dick comes along and pisses on his parade with a completely incorrect rebuttal, which in turn gets Score:5 Informative.
Even if you don't believe that Moz has a chance against Internet Explorer
I quite like Moz and really hope that it continues to get better. My mind is certainly open. Netscape 7 and the new Mozilla's are looking good.
I would actually like to see Mozilla kick arse, especially against IE. I just learned to really hate Netscape and when 6 came out it was like the last straw.
I'm sure the open source community will keep making Moz great. It's just that when I think of Netscape, all I can think of is the slow buggy Netscape of times before open source was able to improve it.
Slashdot Mirror
A lot of places in this world don't have computers, and those people survive just fine.
Very true, but did those places gradually move their way of being towards electrified industry to the point of completely relying on it and then... have those mechanisms of survival suddenly stop working?
I think it would have little effect on most electronics. Perhaps it could even be a positive effect.
You raised some very good points. That I failed to see beforehand.
You actually prompted me to think of antenna design from a DoS point of view.
there is more to it than just an antenna.
I would like to think that security considerations in antenna design should be absolutely minimal. To the point where the only consideration might be for a design on both ends that allows very high rejection of signals that don't come from the intended direction. To avoid any low tech denial of service attacks. Of course, this can be achieved with moderate effort placing transmitters within the line of sight to disrupt the link with an appropriately chosen modulation method perhaps injecting noise, at a power greater than the victim radio links. I say "moderate effort" because this is childs play compared to defeating high strength encryption and authentication methods. Hell, you could even just disrupt the link with some metallic obstacle.
A place I worked at had irregular drop-outs on the inter office microwave which was puzzling. The techs got up onto the roof and saw off in the distance some construction work being done with a crane which was occasionally blocking the line of sight as it moved about. : )
Any radio link should be considered insecure as far as eavesdropping and interception goes, if it does not employ encryption and authentication. But this has nothing to do with antenna design.
An antenna "system" that dynamically configures itself for multiple beams could maybe be coaxed into using up all it's beams into one area, as a denial of service attack. But I think guarding against such a thing could be trivial. All that would be needed is some consistency checking that assures that no channels of the same frequency overlap in the radiation pattern, which could effectively limit a DoS.
Please don't yell at me if I'm wrong... :-)
Don't worry, I won't yell and I won't say you are wrong either. Because what different people consider `active' can be very different things.
I have a chuckle when I hear people in the mountain bike world call their rear suspension systems `active'. I can't help but to think that something that is active, is something that provides certain gains that are "paid for" through external power, whereas a passive device is merely something that passes gains on through efficient designs that merely convert or transfer the power that they receive.
It's a grey area, but as far as I am concerned, a passive antenna includes no powered circuitry to enhance it's performance.
As far as I am concerned, as a purist, an antenna that includes a low noise amp, is a passive antenna with an active assistance device bolted on.
People choose to refer to these as "active antennas" to make them easier to describe, so I can't complain too much about that. As long as I know. : )
(I suppose that big phased array might be really good at picking up weak signals ... is that it?. Hmmm.)
Yes. Gain works for transmitting and receiving.
Second, the article mentions it uses a gigabit connection. Umm...why?
Because having an antenna design/phase manipulation system such as this sharing it's entire range with just 11Mbit/sec would be a complete waste of the system itself.
They must be using multiple channels to better use the bandwidth capabilities of this antenna.
The most amazing part of this will not be if they can actually produce an antenna that comes close to what they are claming
Phased arrays that use manipulated phases to manipulate radiation pattern are not new. They're actually pretty old. I wouldn't be amazed to see them do it.
Using them for domestic use is new though and I'm glad to see it coming.
I see how the directional antenna on the base station can transmit to the roaming laptop that is far away. But, the roaming laptop has a standard internal omnidirectional antenna, how does it transmit back?
Good question, here's the answer: Antenna gain works for the transmitted signal AND the received sensitivity.
Meaning that the directional antenna is not only able to get the transmitted signal to go a long way through a higher effective radiated power by focusing the power in one direction, but it is also able to boost the signal it receives through higher sensitivity through also the same focusing in that same direction. These go hand in hand.
This is in stark contrast to merely using a higher output transmitter in only one radio, which can have the effect of elimination of duplex operation.
When doing 802.11b over long distances, the directional antenna is needed on BOTH sides.
No, wait a sec, keep your mind open. This is not the case. Directional antenna's on both ends will allow greater distances and bandwidth, but if the combined antenna gains, transmitter power, receiver sensitivity, transmission line losses (radio to antenna cabling) and atmospheric conditions allow communications over a certain distance, then the actual antenna radiation pattern (omni vs directional, assuming directional pattern is used to the fullest potential for the claimed gain) will be of no consequence. From strictly an antenna design point of view, the gain is what matters for a given distance to be feasible, not the pattern. But it just so happens that an antenna that provides a narrow beam also can provide a high gain, but that's not to say that this is always a requirement.
An omni direction antenna, being used for point to point is merely wasting the majority of it's output power and not receiving as much remote signal as it could if it were directional. This does not mean it will not work.
Case in point, cell phones: Base stations use directional antennas pointing in different directions (I usually see towers pointing in what looks like 3 separate directions with vertically stacked phased arrays), yet your phone uses an omni directional antenna simply because you the user, can not be expected to point it accurately each time and for the duration of a phone call. Yet, the system works well, because the directional antennas at the base stations make up for the inefficient omni design of your phone with their own high gains in both transmitted power and received signal.
Although years ago there was a Motorola analog mobile phone which actually had an automatically tracking phased array (just two verticals) which the phone would manipulate to track the current base station so as to allow the best reception. I believe this phone never made it to market because one of the techs testing the phone got a cancer near his temple on the side he used the phone and thus the phone got bad publicity.
1> The math behind antenna design theory leaves little room for innovation.
Well, except for the fact that the best antenna designers DON'T UNDERSTAND the complete math behind antenna design theories!
Last time I checked (9 years ago), the formulas for the Yagi directional antenna designs were approximate to the point of requiring trial and error manual tweaking to get best performance, due to the fact that the exact formulas have yet to be found. We have something really close, but we didn't know it all. It was commonly believed however, that the US Navy did in fact know the exact formula, but are keeping it secret.
I don't see where this antenna design is any more efficient than many that are already on the market..
This design dynamically manipulates the phasing of the hundreds of antenna's that comprise the phased array, so that multiple beams can be made, independently directed and track targets without any physical antenna movement.
See the difference in this antenna now? It's not a new concept, but certainly a new concept for WiFi.
2> There are already products on the market that can push WiFi signals well over 4 miles.
Whoa! Now back up a second there cowboy, did you say FOUR MILES! WHOA!
4 miles is nuttin'. I've seen 30km and heard reports of 30 miles.
They might as well be putting out a press release saying they've invented a circular device that they're calling a "wheel".
In the past, I've been guilty of not reading the article. Guess what...
WaveRider Communications [waverider.com] has been selling 802.11 based units with ranges up to 15 km (with outdoor antennas) for several years.
And can this WaveRider unit have a radiation pattern that suddenly changes from 98% at 0 degrees, to 49% 0 degrees and 49% 37 degrees at a moving target which it tracks without any physical antenna movement?
There is the magic and there is the cost. Though it's not really magic, just looks like it, especially when it can be a lot more than just 2 targets.
Yeah, yeah -- they tried to sell me that for my cellphone too. Doesn't work. :)
This is not some silly snake-oil sticker. This is the commercial application of an old technology that has been waiting for one side of it's technology to catch up (although military, etc have used it for many years).
Computing power meets manipulated phased arrays!
PS, they do work, extremely well. So well in fact, that some people will see their claims as snake-oil!
Look into the REAL technology before passing it by.
But most importantly, having hundreds of phased antennas allows multiple separate beams in addition to dynamic changes to (not just the direction but) the overall radiation pattern.
No, this is not new, it's old by military standards, but pretty nifty to see on the domestic market and a really neat application of technology.
They switched it to horizontal polariztion and now we get a good 1.2Mbit+ connection at our site in the middle of nowhere.
Are your techs routing your PABX lines through it also? You can get about 18 (uncompressed) 64k voice lines across that.
The PABX could most likely be set up to first try to route internal calls (and maybe least cost routed external calls) through that link with telco lines as the fail-over to save some money.
Compress those voice channels and get much more.
I worked for a place that had a set up like this at a backup site that housed system developers and entire backup production systems. Pick up a phone and call an extension at the remote site and the call would go through the microwave without the user ever knowing the difference. If the microwave was saturated including the reserved bandwidth for the PABX, then telco lines would be used (a rarity), also without the phone user ever noticing a thing.
I know of an airline company in Sydney that installed a microwave link between the city office and Sydney airport. They routed their internal inter-office calls through it and in the first year, the money they saved from reduced telco bills actually payed for the system and then some.
Mention it to your boss if it isn't being done, its a very worthwhile exercise.
I've never seen any published studies that show this.
Agreed wholeheartedly occamboy. There have been absolutely tons of studies showing overwhelming evidence that ionizing radiation causes cancers and yet tons of studies that failed to show any evidence that non-ionizing radiation (microwaves, mobile phones, WiFi, etc) even slightly highten cancer incidents.
I take that as pretty overwhelming evidence that there is little to no risk with these devices.
Besides that, more effective use of effective radiated power can only serve to reduce overall radiated power.
This technology is older than I am and probably older than most of you too. : )
I have an old FORTRAN text book that has a programming case study about FORTRAN code running on old VAXen being used in RADAR and communications surveillance for the USAF.
The picture in the case study depicts (what is obvious to me as an ex RADAR tech), a few groups of typical RADAR frequency phased arrays.
Back then (late 80's) the technologies I witnessed were amazing, and I have a little chuckle when I see whittled down versions of these various technologies in domestic equipment 20 years later. ; )
I wouldn't get too excited everytime a company comes out with some wireless gadget without documented proof that they actualy made it secure for the user to use.
If you need your wireless network security to be provided by the antenna, you have very serious security problems.
Oh, so now wardrivers can be 2-3 streets away to hack into the network instead of right next to the house? Wonderful.
:)
Hackers have been hacking from streets away long before this came out. Good old high gain antenna designs would allow this with searching done with antenna direction changes as opposed to antenna location changes that driving around facilitates. This new product might just make it quicker and easier to find victim networks.
I'm comming here late, but
/. in the hopes that they can say something vaguely disguised as interesting, informative or insightful to get moderated up before real people with real knowledge who only get to check /. once a day (because they're actually interested in the stories) take their points.
That's OK Kelerain, I'm late on this one too.
But never fear, you have a life and a place in the World right?
People here who usually get in quick often tend to have little valuable to say, since they spend their lives refreshing
The problem is that they are usually quite expensive, take up a lot of space, AND usually require considerable processing
Phased array antenna's don't require any processing at all.
The application of automatic manipulation of the individual phases (in particular designs that allow it), to give dynamic patterns that change with detected requirements, is something that requires considerable processing power.
Consider it a sort of software antenna, you have a series of antenna that you can bias towards a particular direction. You then listen for incoming signals and use a processor to calculate environmental multipath (RF signals bouncing off buildings, etc.) and then fire off your signal so that the main signal and multipath reflections arrive at the reciever at the same time. Instant gain.
This is not a description of a "phased array" antenna design, this is a description of an application of a particular phased array design.
Not all phased array designs allow simple pattern changes based on phase manipulation.
Some can have none, requiring physical antenna pointing, some have simple switched 90 degree changes (forward+back/left+right vertical designs) and then others can be super advanced and highly variable of the likes of military designs with all sorts in between.
BTW, something I really hate about /., is that when I see stuff like this, I feel very compelled to post, rather than moderate (even if I did have moderator points right now).
I imagine this is a feeling most others share, which leads me to the logical and very sad conclusion, moderators are usually ignorant about what they moderate, plain and simple.
Which is why complete crap often gets moderated up and PhD's often get moderated down.
Think of how FM broadcasters get increased erp and still have a circular coverage area.
This is absolutely correct, but does not argue in any way the comment that this reduces the uniform coverage.
You can bias towards distance and not narrow the beam width.
If you compare the two designs you are referring to, but only look at vertical pattern at any one particular horizontal angle, you will actually find, that the virtual "beam" IS in fact narrowed vertically and thus the gain is made possible. Just because it is narrowed toward human population does not make his comments about loss of uniform coverage less true.
We should not delve too far into practicalities and at the same time move away from the technicalities, because we gain the practicalities from the technicalities.
I've been invloved in phased array antenna design and military RADAR since the late 80's. The above comment is NOT Score:5 Informative!
/. Someone posts a comment here that is absolute textbook and then some dick comes along and pisses on his parade with a completely incorrect rebuttal, which in turn gets Score:5 Informative.
1. "phased array antenna" DOES NOT EQUAL "active antenna". A phased array can receive benefits from active circuitry just the same way a simple single vertically polarized "whip" can.
2. "Your statements are true for a passive antenna design." This statement... "You can get more distance in exchange for not getting uniform coverage." is true for any particular moment in time, for EVERY antenna design, bar none. And the whole paragraph of draziw's post stands out glaringly to me, that he knows antenna design practicalities.
Antenna gain depends completely on how well the antenna is tuned for the intended frequency and the radiation/sensitivity pattern it creates.
If you want signals to travel VERY far for example, you could design an antenna that (in laymens terms) compresses it's transmitted power (as in Effective Radiated Power) to a beam, or from a receiver point of view focuses in one particular direction. What this also does, is effectively quieten/deafen the antenna to areas other than that direction intended to communicate with. Thus, his comment about loss of uniform coverage.
Now before anyone argues the virtues of active designs, they MUST consider that the circuitry added to "active antennas" (usually wide-band receiver amplification) does NOT constitute and nor should it, an antenna at all! This is merely a traditional antenna, with active radio amplification which serves to feed ANOTHER radio and APPEARS to be a very effective antenna.
In short, technically, there is no such thing as an "active antenna".
I've been designing my own WiFi massive phased array, a-la flat jet fighter RADAR arrays. I'm currently trying to figure out whether just building a good parabolic design would be easier as the many highly tuned and quite small dipoles would be hard to tune and assemble in phase well enough.
I'll venture it'll cost about $800
I'll venture you don't fully know, that which you speak. I am really starting to hate
I downloaded the song before the "OpenBSD is ready for download" post was on /.
So why is the song, suddenly ready for download?
It's the James Bond'ish, operatic number with the chick with the sexy voice right? Sharp flippers and all that?
Even if you don't believe that Moz has a chance against Internet Explorer
I quite like Moz and really hope that it continues to get better. My mind is certainly open. Netscape 7 and the new Mozilla's are looking good.
I would actually like to see Mozilla kick arse, especially against IE. I just learned to really hate Netscape and when 6 came out it was like the last straw.
I'm sure the open source community will keep making Moz great. It's just that when I think of Netscape, all I can think of is the slow buggy Netscape of times before open source was able to improve it.