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802.11 RF Amp
MikeLRoy writes "Linksys has announced a signal amp, to be available soon, for their wireless ap's/routers. While many people have been using commercial rf amps hacked onto their ap's, linksys now has a commercial solution!" I wonder when ISPs are going to stop soft-pedaling the anti-NATing provisions in their terms of service.
While many people have been using commercial rf amps hacked onto their ap's, linksys now has a commercial solution!
Now if they could just come up with a commercial solution, we'd be all set.
And I'm not even a SpeakEasy customer. I wish RoadRunner would implement similarly "with-it" policies...
"BSD: Free as in speech. Linux: Free as in beer. Windows 10: Free as in herpes." --Man On Pink Corner in #52607549.
Actually, this device increases the RX sensitivity and power as well as that of the TX, thus giving a greater range regardless of what you have in your laptop.
Erm, no... it's a signal amp... so if you stick it halfway between a laptop and a wireless AP, it will amplify the signal from both. It's just like using a repeater in a cabled network.
"If at first you don't succeed, lower your standards."
Because this device emmits at the FCC max, something most APs do not. Yeah, this thing would rock inside a Pringles can, but it's likely even the worst designed can will put the setup over the limit.
Unless you start snooping into the data packets, looking for User-Agent strings, etc (if you're NATting 2 different OSes behind it). You can make educated guesses (why do all TCP connects come from port 61000+?) but you really can't KNOW if someone is NATting.
I want to delete my account but Slashdot doesn't allow it.
Balam
If that would bring down your ISP, get a new ISP.
...but ours goes up to 11.
Get yours here!
Karma: Censored (mostly affected by decency laws)
The entire point of 802.11b is that it is low power, allowing a lot of use in a small area. If my neigbours all start to boost their signals (both ways of course), my 2.4 GHz RF environment is going to be be useless. X.10, cordless phones, bluetooth, 802.11b all share this frequency (and I have all four of those at home...)
In the UK, until recently 802.11b was illegal for commercial use because it was full, making it useless. My car the other day would not open in a high-RF environment (near Toronto's CN tower).
Can we please keep this frequency useable? Amplifying will kill it. An RF signal of this type can carry 30 miles very easily, making it useless if we all start amplifying.
Michael (radio amateur, VA3MVW)
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I'm sorry, but that's no way to run an ISP. An ISP should provide some degree of insulation of customers from one another. There are a lot worse things that people can do by accident, or deliberately, than "plug in a NAT backwards".
I don't like the idea of amps for 802.11.
:)
People seem to be getting excellent range out of very low power devices using fairly cheap antennas!
Pumping out more power will just increase interference with other 802.11 networks in the area. Not to mention it would almost certainly be illegal in the UK to use one of these things
Ah... I open it with an RF-operated key (it's a Mercedes). And no matter how I pressed, nothing happened. MOst disconcerting. From using my radios I know this to be a high-RF environment. I could open the car using a metal 'emergency' key, and once away from that area, all worked OK again.
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I dumped my Comcast cable modem for SpeakEasy DSL just about a year ago, and I've never been happier with an ISP.
I've never had an outage, I can (and do) run servers in my house to handle my own mail, www, etc. Their phone reps are courteous and don't suffer total brain shutdown when I mention the magic sentence, "I'm using a Mac."-- not that I've needed support beyond a little help sorting out a password issue when I wanted to configure the INCLUDED dial-up access in case I needed it.
When I needed an additional IP address last year, I called them up and had one in a couple minutes. I just upgraded my service from 608K down/128K up to 1.5M down/384K up, and it was not a hassle at all. Since my employer chips in $50/month of my ISP charges, this higher speed service now costs me $40 per month, the same I was paying a year ago for my cable modem with all of its restrictions.
To all Slashgeeks who are able: If you have a choice, go with SpeakEasy-- you won't regret it!
~Philly
I'd be a lot happier if the FCC got rid of some of those UHF TV channel frequency monopolies and gave the spectrum back to the public that rightfully owns it, to try to lower contention over the narrow strip of bandwidth that 802.11 uses. There's also much more use of wireless these days by non-mobile devices than there really needs to be, when those devices could perfectly well use wired ethernet, or maybe a much lower-powered shorter-range wireless scheme (like a higher-bandwidth Bluetooth) to an access point that's nearby (i.e. in the same room or close to it, not far away in the building). However, that last part is harder. Tragedy of the commons and all that.
LOL ok yea it's posible allthough doubtfull any DSLM worth it's salt dosent forward DHCP responce packets in from the CPE and dosent forward DHCP requests out to the CPE end either. If a small ISP has missed bridge configuration 101 (Yes most DSLAM's especialy cheap ones are simply bridges) but in my state at least the DSLAM is actualy the Telco's the small ISP gets a single ATM connection into there cloud and PVC's are setup for each port to there router generaly running PPPoE to that router. The first thing you do after you get it working is get it secure (yea I know it's nice ot say secure first but for a small company working is normaly more of a priority than secure) BTW if you were to actualy worry about this they shouldent allow windows boxes turn on ICS the wrong way and you have a DHCP server on your cable modem / DSL. Oh Cable modems may have more of an issue with this they would have to filter at the cable modem or the head end (I dont think any of the cable modems can receive on there transmit frequencies at the same time so any modem to modem connection need to pass through the head end? Would like to be corrected if I'm wrong on this I dont nroamly deal with this low end gear :)
No sir I dont like it.
The Wap11 Hack courtesy seattle wireless.
;)
Basically using a different firmware/snmp agent for a different ap based on the same chipset you can up the signal strength at no charge. It is risky however, so I take no responsibility blah blah blah. Maybe thats all the amp does is up the built in power..
That's not entirely true. If the signal going FROM the hub to the laptop are strengthened, the data transmission would definately be improved, but in most cases, one can also improve the "reception" capability of the hub by boosting the recieving antenna gain. But by the same token, these systems run full duplex (transmit and recieve at the same time), so if the transmitter is boosted, it COULD concievably de-sensitize the reciever.
Not sure of the exact machanisms IF the hub actually transmits and recieves at exactly the same time, but now that I think about it, perhaps not (being digital - it COULD be simplex).
If you've even been near a powerful FM or even a TV transmitter, and try to use an FM radio, you would be hard pressed to pick up anything else BUT the FM transmitter.
RF can get into ANYTHING... as a 1st class FCC license holder, and former Chief Engineer of a 25KW FN station, I know only too well what RF can do. Ask your food, when you take it out of the Microwave oven.
A while ago on slashdot there was breathless coverage of a Linksys hardware 'hack' that raised their 30mw AP to 100mw. Some knowledgeable RF engineer took a look and it *was* putting out 100mw - 31mw in channel, and 69 mw of crap spattered all over 2350 - 2550 MHz. All that 'hack' accomplished was giving more ammunition for those satellite radio folks that want to regulate the ISM band.
Instead of building a 100mw radio with good sensitivity, Linksys is building a cheesy amp to go with their cheesy AP.
If you genuinely need some amplification I've used YDI.com and Teletronics.com amps in the 250mw to 1 watt range and not had much trouble with any of them. RFLinx or RFLynx(sp?) has come out with a 750mw amp for $200, but I haven't tried that product yet.
FYI half of the reason to deploy an amp is for the LNA (low noise amplifier) effect - besides boosting output they pump up the return signal by 10 - 14 dB. There is a real call for a 150mw output amp with a solid LNA for client side problems, but that is a story for another day.
I am very easy to get along with, but I don't have time to waste being nice to people who are being stupid. -Theo
I don't think you need to worry. What Linksys is doing is not nearly as interesting as people might assume (which is I suppose is par for the course for Slashdot :-) What I'm pretty sure is going on is that the wireless access point on the linksys doesn't have a very strong radio transmitter to begin with (I'm guessing 30-50mW), and the signal amplifer just raises the transmit power to the max legal limit for the 2.4GHz band.
The Cisco 350 Access Point (and wireless cards) has better receive sensitivity (I don't know if that's due to a better built-in antenna, or better radio circuity, or both), and a stronger transmit power than most other 802.11 cards (selectable from 5mw to 100mW). In contrast, the Lucent Wavelan Silver card has a 31 mW transmitter. I don't know what the transmit power for the Linksys access point, since it's not listed on the web site or in the user's guide, but they claim an outdoor range of 1500 feet at 1 Mbps, and 500 feet at 11 Mbps. For comparison, the Orinocco access point claims 1750 feet at 1 Mbps, and 525 feet at 11 Mbps, and the Cisco 350 access point claims an outdoor range of 2000 feet at 1 Mbps and 800 feet at 11 Mbps. If we assume that both Cisco and Linksys are exagerating to an equal extent for the best case scenario, it seems pretty clear that the Lucent transmitter is less powerful than the Cisco 350.
Of course, as radio amateurs know, transmitter power doesn't have as much effect on range as some people might think. That's why QRP operators can sometimes communicate with people halfway across the globe with only a Watt or two of power. So the Linksys signal amplifier will probably not make that much of a difference.
That being said, I would recommend the Cisco 350, not because of the higher transmit power, but because the access point has better manageability (you have much finer control over how the access point operates, with various nice features such as having the AP ask your radius server whether or not a particular MAC address should be allowed, LEAP authentication/encryption, etc.). Also the Cisco 350 PC card has a full-featured Linux driver, which allows you to control the transmit power, scan for all available 802.11 networks, and so on. Another nice feature with the Cisco 350 is that you can store the WEP keys in flash memory, so that you can lend the card to house guests, without needing to reveal the WEP key. (Right now, I haven't been able to find an open source radius server that supports LEAP, so I'm using a combination of 128-bit WEP keys plus MAC address access controls. One nice thing about the 350 Access Point, as compared to the Apple airport, is that you can change WEP keys without needing to reboot the access point. So while I haven't implemented it yet, it should be possible for me to automate changing the WEP key every 24 hours, by calculating a MD5 hash of a secret plus a timestamp. That way, a shell script on my Linux laptop would allow me to get update the WEP key at the same time, automatically.)
-Ted (N1ZSU)
Actually, like puzzled (12525) posted: "FYI half of the reason to deploy an amp is for the LNA (low noise amplifier) effect - besides boosting output they pump up the return signal by 10 - 14 dB."
Give him the karma. And mods, why the hell are you modding up this post's parents, and it's parent's parent?
The amp doesn't go halfway between anything, and you don't need a similar device on the other end.
-Berj
I wonder when ISP's are going to realize that it is futile to say "no NAT" or "no servers" or "max transfer gb per month" and realize that the only sane thing to do is to provide unrestricted access, and simply charge their customers what it actually costs to provide xx mb of bandwidth?
Let's not beat around the bush. Heavy users pay for heavy bandwidth. Light users pay for less bandwidth, and get less bandwidth. Trying to weasel out of providing less than the amount of data that the pipe can carry is a waste of everyone's time.
Tired of FB/Google censorship? Visit UNCENSORED!
This is a SERIOUS consideration anymore, no place in the world is "immune" to terrorist events, and it's only a matter of when-not if- that RF/EM devices start to be used. And to me "who" uses them isn't as important as "they will most likely be used". It's too good of a weapon to think it WON'T be used. This is my opinion of course, but I think it's something to consider.
That amplifiers amplify everything... including the ambient noise PLUS they also insert a certain amount of noise themselves (LNA stands for "low-noise-amplifier not no-noise-amplifier). So while the signals may be amplified, the noise level might also be amplified enough to negate the effect.
In addition, the FCC has a dba limit on the amount of signal you can have so you cannot just stick power amplifiers on all the devices in the network without incurring some exposure to fines and penalties (for interference).
It makes a lot more sense to design the wireless system to use numerous low-power devices spread around the area so that you can cover just what you need to cover and not simply saturate the area with signal.
No one ever had to evacuate a city because the solar panels broke!
If your aircraft transceiver is running on 2.4 GHz, you've got bigger problems than renegade WiFi networks.
Dahlmann tightly grips the knife, which he may have no idea how to use, and steps out into the plain.
> Would you like it if the phone company said you
> could only have 1 phone on your line,
The phone company did just that for more than half a century. In fact, they did not allow customers to use their own phones at all. We were supposed to rent phones from them.
I agree, though. ISPs should sell metered service and charge by the byte.
Warning: this article may contain humor, sarcasm, parody, and perhaps even irony. Read at your own risk.
Errr... there is no longer a 1st class FCC Commercial License. Mine turned into a "General Class" a couple of decades ago. Second class also turned into a "General Class."
(for those who ask, this is a kind of license needed to be a technical person on various kinds of FCC stuff, such as two way radios and broadcast stations). The term "engineer" in broadcasting is like the term "engineer" in trains - it doesn't mean you are an engineer. I started as a broadcast "engineer" when I was in high school with a 1st class FCC License (commonly called "First Phone").
The only good weather is bad weather.
Why does my ISP care how many computers I hook up to my network? I'm paying for the bandwidth.
No, you're paying for a personal internet connection. If you were paying for bandwidth, it would likely be more expensive and they wouldn't care what you did with the connection. That said, it shouldn't matter what you do, so long as you don't abuse the service, say by downloading stuff 24/7 or having 4 or 5 people using it all the time.
Would you like it if the phone company said you could only have 1 phone on your line, or the power company said you can't share electricity with your roommates? I didn't think so.
Well, it's already been mentioned that the phone company did just what you describe. Your analogy is flawed. Having more than 1 phone on the line doesn't affect the load on the phone company - you can only make 1 phone call at a time. The power company charges you based on usage, and at a higher rate if you exceed a set amount per mnonth, so why should they care?
"We returned the General to El Salvador, or maybe Guatemala, it's difficult to tell from 10,000 feet"
> No, you're paying for a personal internet
...and they wouldn't care what you did with the
...it shouldn't matter what you do, so long as
...or having 4 or 5 people using it all the
> connection.
But what I want to pay for is bandwidth usage.
> If you were paying for bandwidth, it would
> likely be more expensive...
Why?
>
> connection.
That's the point.
>
> you don't abuse the service, say by downloading
> stuff 24/7...
Not likely with one phone line used for personal calls, business, and the computer.
>
> time.
Two people, and usage that is probably below average.
Warning: this article may contain humor, sarcasm, parody, and perhaps even irony. Read at your own risk.
The new NAT mechanism implemented in the Linux 2.4 kernels tries to use the same source port as the translated packet. I suspect other NAT implementations might be doing the same.
What I wish linksys would allow in the firmware was a mac address allow list. Right now you can only set mac addresses to block from the WAP. Kinda stupid if u ask me, why not list the mac addresses you want to allow. I know that they can be spoofed, but it makes it just THAT much harder
Most folks I know of here in Columbus who have more than one computer use NAT. Mostly Roadrunner. A tech was out and seen my setup and they said nothing. Only thing they said was t would be slower (BS). In facet I think they support you doing things like NAT. Saves them equipment and IP adresses.
Gorkman
Since 11Mbps is a tasty target, it's hardly surprising that people will be gunning for maxing out what 802.11 will do.
Maybe the better thing to have done, rather than come out with a single wireless protocol would be to have two; one that would do 50Mbps but at a range of no more than 50m, and another good for 50 miles but at no more than 250Kbps, with a large number of channels.
The former would be great for offices or other places that need high bandwidth, but the distance limitation would have kept it from being so popular as a last-mile. The latter would be awesome for linking buildings or other long-range applications, but a large channel count and low bandwidth would keep people from trying to replace T1s between buildings..
YMMV, but SBC Yahoo / Ameritech doesn't care about NAT. In fact they acknowledge that customers may be connecting more than one system in their customer support materials. The downsides:
-Non windows / mac OS support doesn't exist. They run a don't ask don't tell policy when it comes to multiple PC's, but you need a windows PC for them to do any sort of trouble shooting. (My guess says their support people are reading from a card)
-Installation (from the telco side) is intermittent. Some people I've talked to get setup in a couple weeks. My setup took just shy of three months. To be fair, my order went in just a few days after my area went DSL ready. half of their systems said I could have DSL, the other half didn't. I had two separate orders canceled by the compliance check.
SBC Yahoo may be a good option for your area. sure comparing it to Comcast / Roadrunner is like comparing genital warts to Leporasy (you don't really *want* either, but one's probably a bit easier to live with). It may be wrth investigating. I'm running wireless + two regular boxen and they (officially no less) don't care.
And if you do setup a network remember; http://www.coyotelinux.com, because if you buy a router from best buy, then the terrorists have already won.
There are some people that if they don't know, you can't tell 'em.
Ted,
Mmm.. I wish I could be as much of an optimist. I have recently noticed that 2.4 GHz seems to be getting fuller. My MAME box in the basement sometimes will not see the wireless access point upstairs, and I suspect it's due to QRM - in other words, to the neighbours doing stuff (X.10, phone, etc) in the same frequency range. Power isn't everything (with 10W on 6m I have worked SCotland), but this is line of sight, and surely raising the power from 40 mW to 250 mW will enable more distant neighbours to add to that problem. Bluetooth uses 1 mW by the way, which gives 10m range. Power isn;t "nothing" either!
73
Michael
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I used to be a radar tech. I used to fondly call the things and open air microwave oven.
Which brings up the usual questions of frequency range and power. One or two probably are no great shakes, but a Special High Intensity Test would be needed if you had a bunch of them
"It is a greater offense to steal men's labor, than their clothes"
The fundamental design flaw. I would rather eat sand than that crap. My dog seemed to agree.
You can't judge a book by the way it wears its hair.
Would running a proxy server be harder to detect? I run squid and have all of my home pcs connect to the web through it.
http://www.windmeadow.com/
Apparently the key also communicates with the ignition system through IR... there's something that looks like an IR receiver in the well where you insert the key.
--Larry
Never attribute to malice that which is adequately explained by incompetence
It is just a repeater. It doesn't broadcast at any greater strength than your typical 802.11b access point, all it does is repeat whatever it picks up, thus increasing the range.
I wonder whether Linksys will include an upgraded antenna in their signal booster kit instead of the little rabbit ears that their current access points come with. For about $100 you can get a 10 decibel gain antenna (for example, see www.telexwireless.com.) Add a 10db gain omni to an amped signal and we may really be able to get some distance out of 802.11b!
:) Click that white button and turn it green.
What the world needs is fewer karma whores and more good friends.
Go ahead, friend.
http://tinyurl.com/4ny52
The logic goes that you have to certify with a known antenna, so if you use standard connectors anybody could hook up a different antenna and make the device noncompliant...
and yes, it sounds screwy to me too, but those are the rules
As someone who has worked for an ISP, I can tell you that the majority of the traffic comes from a minority of the customers. I haven't worked for an ISP that's had DSL service, and so, I see it from the point of view of dial up. In fact, I'm going to assume that the AUPs in question stem from dialup related problems.
You see, the issue is that phone lines cost money. For us, it was costing us almost $70/month, [business lines are more expensive than residential lines, and well, they were PRIs], plus the cost of hardware (modems, servers) and other costs (staffing, office space, internet connection). The only way to make a profit off of modems is to NOT have someone sitting on 'em 24hrs a day.
Although we didn't get picky when a whole family was using their connection, we would start asking questions when someone was on more than 500hrs in a month (as well, we expect people to sleep once in a while). Sometimes, you get more than one person in the house who's an addict, and they're working different shifts... normally, it's someone who has their mail program set to check every 5 minutes, and they've got dial-on-demand set up.
So, to make up for this, and so you didn't have to completely kick people out, there were normally additional tiers of service. Many times, they were just listed as 'business' and 'residential', or they might have some other name for an always-on-connection, or where it was okay to be sharing out the line -- because the more computers using the line, the more likely it was to be up all the time.
Now, with DSL, the model has completely changed, so that doesn't entirely fit, but have the ISPs changed their AUP? Doubtful. And if they did, they'd probably have to have one for broadband connections, and one for dialup, and then you've got to have seperate tracking of users, etc. Of course, your bottleneck problem now isn't busy modems, but your connection to the internet -- so people downloading every mp3 they can find, divx movies, etc, start cutting into your bottom line. [And well, you've either got to lose money on each individual that's doing it, or get rid of 'em so they don't adversely affect every other customer.]
Oh, and for those wondering...I am a speakeasy customer...only outage I've had was when they changed my IP address. [and they even called me the day before to remind me it was going to be happening... but I wasn't at home, and forgot to write down my new IP, and I had it saved in e-mail, so I had to go to the local library the next day, and check my mail from there to get my new IP]
Build it, and they will come^Hplain.
I think you are confused as to what an amp is and what it does and doesn't do.
An amplifier takes raw signal (including noise) and amplifies the power on it in the direction it is set to amplify. There are bidirectional amplifiers to do it in both directions.
Amps are best placed as close to the antenna as possible to reduce loss and noise. As a signal travels across cable, noise and loss increase. Thus, a short "jumper" cable is ideal to connect the antenna to the amp.
Putting an amp on one side of the communication pathway will improve the signal and perhaps the distance a bit. The biggest improvement will be in the quality of the wireless link at the far reaches of the original signal.
To greatly improve distance, it is absolutely necessary to amplify on both ends. The end goal is to improve your signal to noise ratio. The weaker your signal from the other end, the worse that ratio becomes.
Buy what I want to pay for is bandwidth usage.
That is not what you bought. Your options are: business class DSL, various kinds of leased lines, and colocation. Wireless is sometimes an option, but that isn't widely available.
Why?
All your options for paying based on usage are expensive. If you just want a server, colocation and managed hosting are likely your best bet.
Two people, and usage that is probably below average.
So why are you bitching? Your ISP may care, but it can't find out and, unless you make a big stink, they won't care about you beyond your monthly check. In all seriousness, if you care about your ISP and its posturing, then switch. If you can't, then keep your head down and donate to a lobbyist group that represents your interest. That's how Democracy works in the US.
"We returned the General to El Salvador, or maybe Guatemala, it's difficult to tell from 10,000 feet"
In many ways, 802.11b Access Points give you similar performance to what you would find in a 10BaseT hub
It is actually a bit worse. Bad signal levels, noise, multipath and other issues conspire to make the throughput of the average "11Mbps" 802.11b network lower than you would expect on a regular 10Mbps 10baseT hub with a similar number of clients.
Clients scale back to 1, 2 or 5.5 Mbps if the signal quality is not sufficient for 11. A client sending 1K of data at 1Mbps use the same air-time as a client sending 11K at 11Mbps.
On a shared hub, all clients can 'see' each other, so when two nodes transmit at the same time they detect a collission. On wireless, you can have hidden nodes (both clients can hear the AP, but they can't hear eachother) so you can get collissions but the clients don't know that they collided. To mitigate this problem, you can revert to an RTS/CTS system (AP tells nodes when they can send) but at the cost of lower throughput.
2.4GHz is also becoming crowded. Bluetooth, DECT phones and other equipment also use the same frequencies. This creates more noise and interference.
Etc..
When having more than a few clients, expect aggregate thrughput on 802.11B to be closer to 4-5Mbps than 11.
If J.K.R wrote Windows: Puteulanus fenestra mortalis!
Just read a web site about a ham "working 500kms on 3cms with 2.5W on Rain Scatter". That is 500 kms' not the 50 km I was talking about. Rain scatter!!
See http://www.neoamateur.org/
Mike va3mvw
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What you're ignoring here is that the receiver has a limit on its sensitivity - So that even if it is receiving a signal with a good SNR, if that signal is too weak, it will be below the noise floor of the receiver itself.
Adding a preamp boosts that signal. Yes, it amplifies the noise, but it will bring the signal above the receivers' internal noise floor. The most important factor in the noise performance of a receiver is the noise figure of the very first gain/loss stage after the receive antenna. Put in a low-noise gain stage here and the NF of the entire system drops. (This is why satellite receivers have a preamp at the dish, not at the receiver at the other end of the coax, and why broadcast TV amps should be at the antenna, BEFORE the coax run)
WLAN receivers (especially budget ones like Linksys, D-Link, and almost any mainstream Prism2/2.5/3 implementation) usually don't have the best receive sensitivity because a good preamp at 2.4 GHz costs $$$. This preamp is a cheap way around that problem.
If you want a good example of why a preamp will help you - Use Kismet (a passive receive-only monitor) with:
a) A Prism-based card
b) An Orinoco card
c) A Cisco card
You'll notice that given almost identical antenna designs and identical signals at the receive location, the Prism-based card has horrible receive sensitivity, the Orinoco is INCREDIBLY good (compared to the Prism), and the Cisco is even better. (Not as much improvement as Orinoco vs. Prism, but still noticeable)
Note: High-end Prism-based cards like the Demarctech ReliaWave are exceptions. The Reliawave beats Orinocos and even Ciscos I believe.
So you can get a LOT of receive performance improvement with just a transmit power amp/receive preamp on one end. Especially when the receiver in the AP isn't particularly hot. (I think most APs are better than cards, but at the card end, you'll see a lot more benefits from adding a preamp to a Prism based card than to an Orinoco or Cisco card, since the Prism has the worst receiver and as I mentioned before, the very first gain stage is the most important.)
retrorocket.o not found, launch anyway?
802.11 is not full-duplex.
To the user, it may appear full-duplex because it switches between transmit/receive extremely quickly, but it's not full-duplex, just like 10 or 100baseT on a shared hub is not full duplex but without extensive benchmarking in a high-load situation, the user can't tell that it isn't FDX.
Do a search for N9ZIA - The guy is a bit nuts, but has done a LOT of 802.11 hacking, including some major mods including bidirectional amp ideas for Proxim's 802.11 precursor products. (Not 802.11, but very similar)
retrorocket.o not found, launch anyway?
I haven't seen any specs, but I have a feeling this doesn't emit at the FCC max.
In fact, I wouldn't be surprised if it's not anywhere close to the power output of some of the $300-400 range of bidirectional amps - I can't find specs on Linksys' website, but I wouldn't be surprised if this only boosted the signal to 100-200 mW. Legal limit into an isotropic antenna (or is it a dipole?) is 1W.
Also, FCC regs on the EIRP are a bit odd - There isn't an exact fixed limit on EIRP, i.e. for every 3 dB of antenna gain you add, you don't have to drop transmit power by 3 dB - It's only 1 or 2 dB or power you're required to drop.
http://www.qsl.net/n9zia/wireless/page12.html has specific info.
+30 dBm max output at the product's connector
+36 dBm max EIRP for multipoint connections
For fixed point-to-point connections, the PEP of the transmitter must be reduced 1 dBm for every 3 dB of antenna gain beyond 6 dB.
i.e. with a 6 dB antenna, you may run 30 dBm (1W) output power, for an EIRP of 36 dBm. With a 9 dB antenna, you must drop to 29 dBm output, for an EIRP of 38.
At 20 dBm output (100 mW), you may run 36 dB of gain
At 23 dBm output (200 mW), you may run 33 dB of gain
If the max output of this amp is only 20-23 dBm as I suspect, then not even the best Pringles antenna won't be able to push it beyond the legal limit. Only a large high-quality dish will have a chance. (33 dBi is a LOT of gain. The largest parabolic antenna at http://www.fab-corp.com/ only has 24 dBi of gain)
retrorocket.o not found, launch anyway?
Why don't I ever have mod points when I need them?
The device, while so far light on specs, is marketed as an amplifier, not as a repeater. From Linksys' product page - "The Linksys Wireless Signal Booster piggybacks onto your Linksys Wireless Access Point (or Wireless Access Point Router)"
Repeaters don't "Piggyback" on the AP. They're placed elsewhere.
Also, if you look at the picture, esp. the enlarged one on buy.com's product page, you'll see that the booster is stacked on top of an AP in the pictures - WITH COAX RUNNING FROM THE AP TO THE AMP. Also confirmed on Linksys' product page - "To install, just stack the Wireless Signal Booster on your Access Point, move the antennas to the Booster, and attach the Booster's twin cables to the Access Point -- no drivers or modifications to your setup are necessary."
retrorocket.o not found, launch anyway?
a) 2.5W = 2.5 times the FCC legal limit for 802.11
Also, thy were probably using a very high-gain antenna on top of that 2.5W of transmit.
Last but not least - They were almost surely using CW (or *MAYBE* PSK31) - Which have bandwidths measured in *hertz* not megahertz.
The closest comparison to this would be taking a magnetron from a microwave, putting it into a feedhorn, and using that to communicate.
(Actually, hams DO things like this - Use a PLL to clean up the magnetron's signal, and then use it with a big dish for EME (Earth-Moon-Earth) work)
retrorocket.o not found, launch anyway?