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FCC Allows Mix-and-Match Wi-Fi Antennas
Glenn Fleishman writes "We just filed a story at Wi-Fi Networking News about how the FCC recently and quietly approved rules that will allow the legal use of the Pringles can and other antennas. Currently, it's clearly illegal--even though it's incredibly easy--to swap out a manufacturers' antennas from a Wi-Fi access point with an antenna of your choosing. It's legal to sell antennas; not legal to deploy them. Call it the switchblade kit rule: legal to sell, but don't assemble. The FCC's new rule provides a middle ground: a manufacturer can certify their hardware with the highest gain legal antennas of each type (yagi, omni, etc.) and then end-users can swap in antennas of equal or lesser signal characteristics. It's an important move because it removes the potential for community wireless and individual users to be prosecuted for illegal antennas once new certifications are in place."
Does this mean that we can finally get rid of annoying antenna connector types such as RP-SMA and RP-TNC that were originally devised just to make it a pain in the ass to switch out factory antennas? I'd much rather be able to mix and match antennas and cables that can be easily found at local HAM shops.
you can also use a peice of cardboard and aluminum foil http://www.techtastic.ca/articles/homemade-antenna .html
Doesn't this mean quite the opposite - if you have an antenna of questionable legality right now, after the certifications are in place it will become an uncertified and illegal antenna?
Channel 1 is in a band that falls in spectrum assigned to amateur radio operators. That means, of course, we can legally transmit up to 2500 watts vs 50 milliwatts if that happens to be the lowest power we need to get the signal through.
It also means we're licensed users of the spectrum, which trumps Part B and means a license holder could, technically, tell a neighbor to move off of channel 1.
I noticed that the article lists a bunch of different antenna types. I didn't know what they all were, so I looked some of them up and thought I'd share:
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The info in quotes is verbatim from http://www.radiolabs.com/Articles/wifi-antenna.ht
Omni: (Omni-Directional)
This is a standard antenna like you'd see on a cordless phone. Broadcasts the signal more or less equally in all directions.
"An Omni-Directional antenna would serve as your main antenna to distribute the signal to other computers or devices"
Yagi Antennas
"Yagi antennas were the design of two Japanese people, Hidetsugu Yagi and Shintaro Uda, and are sometimes referred to as Yagi-Uda antennas...these antennas are typically very directional and are used for point to point."
Yagis look like a ladder with one vertical bar in the center of each step.
Backfire antennas
"The backfire is a small directional antenna with excellent gain. They look similar to a parabolic dish, but the gain isn't as high."
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Witty movie reviews, eating contests, and a guy who once drank a gallon of milk in an hour.
How is it clearly illegal? I didn't know it was illegal to use your own attenas?
Yes, because license-exempt transmitters ("Part 15" devices) are approved based on a specifc design including the antenna.
Once you modify a Part 15 device, such as by using a non-approved antenna you modify its RF characteristics which change important details such as how much Effective Radiated Power (ERP) which is limited to 4W in the US (many European contries limit WiFi to 1W ERP I believe).
If any one wants to use highpower 802.11 on 2.4gh and use huge wave guide antenas with that high power equipment then all they have to do is get a ham lisense. With the introductory lisense you can use super high power out put transmitters and realy high gain antenas compared to the comercialy avable stuff. How would you like 100 wats PEP on your access point? The only thing is you cant use it for comercial purposes only personal uses. If you get the liscense you also get access to other bands and you can legaly build your own radio equipment. Its not hard to get the lisence either and there are probaly tons of hams in your area to help you get into and promote radio hobbies like packet radio. Check out www.arrl.org, or www.qrz.com if you need some more information.
Faith_Healer -- The antethsis to almost everything, and the worlds worst speller.
Many WiFi products are low enough power that you couldn't violate the standards with any antenna.
The blurb states, "FCC recently and quietly approved rules that will allow the legal use of the Pringles can and other antennas." This is clearly false, since those antennas were already legal to use.
The point of the power limitation is to restrict the signal strength, and thereby reduce interference.
So Tom, Dick and Harry have houses in a row. If each one has nondirectional antennae on his home network, none of them receives network packets coming from another's house. But if Tom and Harry set up directional antennae so they can network together, Dick will receive packets from both Tom and Harry, and his throughput will go down.
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15.204 External radio frequency power amplifiers and antenna modifications (c) Only the antenna with which an intentional radiator is authorized may be used with the intentional radiator.
Now, it says:
15.204 External radio frequency power amplifiers and antenna modifications (c) An intentional radiator may be operated only with the antenna with which it is authorized. If an antenna is marketed with the intentional radiator, it shall be of a type which is authorized with the intentional radiator. An intentional radiator may be authorized with multiple antenna types.
(1) The antenna type, as used in this paragraph, refers to antennas that have similar in-band and out-of-band radiation patterns.
(2) Compliance testing shall be performed using the highest gain antenna for each type of antenna to be certified with the intentional radiator. During this testing, the intentional radiator shall be operated at its maximum available output power level.
(3) Manufacturers shall supply a list of acceptable antenna types with the application for equipment authorization of the intentional radiator.
(4) Any antenna that is of the same type and of equal or less directional gain as an antenna that is authorized with the intentional radiator may be marketed with, and used with, that intentional radiator. No retesting of this system configuration is required. The marketing or use of a system configuration that employs an antenna of a different type, or that operates at a higher gain, than the antenna authorized with the intentional radiator is not permitted unless the procedures specified in Section 2.1043 of this chapter are followed.
Apple, on the other hand, probably has no plans to sell replacement antennas for its Airport devices and will only get certification for its standard antenna.
Perhaps a poor example, since all current Airport Extreme models have an external antenna connector...
For reception, you can use whatever antenna you like, as long as it doesn't pose a safety hazard to the general public, and you have permission to erect it (if required by local building codes.) In other words, if you want to use that chain link fence (for reception only) that goes along the back yards of the next 20 houses, you can. Just make sure that if you do decide to transmit with it, you aren't exceeding part 15 rules, or those of your license class, and the environmental safety rules that require minimum seperation between transmitters and living things.
BAN BPL! Keep the radio spectrum free fro
What about this rule:
15.247(b)(4) Except as shown in paragraphs (b)(3)(i), (ii) and (iii) of this section, if transmitting antennas of directional gain greater than 6 dBi are used the peak output power from the intentional radiator shall be reduced below the stated values in paragraphs (b)(1) or (b)(2) of this section, as appropriate, by the amount in dB that the directional gain of the antenna exceeds 6 dBi.
Why would the FCC worry about the gain on these antennas?
Because Part 15 for license-free (or license-exempt I can't remember which term they use officially) limited the total effective raditated power (ERP) to 4W, and a limit of 1W transmitter. So you can use a up to a 1W transmitter and a 6db gain antenna and remain within the Part 15 limits, or a lower power transmitter (typically 100-250mW with WiFi) and a higher gain antenna.
Someone please explain why High Gain antennas are/were evil to the FCC?
Because license-free devices have no protection and are suppose not to interefere with licensed "services" (official term) in the same frequency band (2.4 GHz has several users including Industrial, Scientific and Medical usage, and I believe some satellite downlinks are also in 2.4 GHz).
Modified devices may create intereference on harmonics (normally non-approved amplifers are most common cause of harmonics). The limited gain of antennas limits intereference between license-free devices and licensed devices.
There are federal laws that prohibit interstate transport of automatic knives, however in most states they are legal to purchase in buy, and in many they are legal to carry with some restrictions. Here's a list by state: http://www.amatecon.com/switchblade.html
No, you are never going to get enough power out of a Part 15 device to do any damage. In fact I've stood in front of an antenna powered by a 200mW radio which had WAY more gain then you can legally have for an 802.11b fixed point installation and there was zero damage. The RF engineers said that so long as the power was under 50W there was basically zero chance of any damage, even that extreme setup only put out around 5W. Microwave ovens operate by bombarding hundreds or thousands of watts of energy into a relativly small volume of food. You could accomplish the same amount of cooking if you could push a resistive element the same amount of power with the same efficiency.
There are 4 boxes to use in the defense of liberty: soap, ballot, jury, ammo. Use in that order. Starting now.
You miss the point ... the manufacturers can qualify their equipment with very powerful antennas. I don't believe they have to -sell- those more powerful antennas. So Linksys could qualify a WRT54G rev3 with a different, more powerful, antenna but continue selling with the wimpy ones they have. Then if I want to go to Radio Shack and pick up the more powerful antennas for $20, I can do so so long as they are equal or less than the power of the -qualified- antennas.
/. over a high speed link to my ISP. In the future, if the bridge manufacturer certified an antenna of equal or -higher- strength, I could keep using my antenna without breaking the law. That doesn't mean that they are going to sell that $120 bridge with a $100 antenna ... only that they qualify it.
Of course, this probably means companies will start doing things to make their connectors hard to match so you have to buy a name-brand antenna rather than a BNC connector antenna from Radio Shack (alot of products already do this).
So for instance at my house I'm breakin da law by having a directional high gain antenna connected to an 802.11b bridge so that I can do things like post to
It is more productive to voice thoughtful opinions (reply) than to judge (moderate) others.
The pringles can antennas work really well. I've built two of them. There's plenty of really good guides on how to make the antennas and how they work.
It's pretty hard to exceed the legal limit for antenna gain with a pringles can (unless you're using it in conjunction with an amplifier). 15 dbm card + 12 dbi cantenna = 27 dbm effective radiated power, which is significantly less than 36 dhm erp (4 watts), which is the limit for most applications.
See also part 15 section 23 (home built devices), which seems to imply that its perfectly okay to build your own custom antennas in some situations regardless of what the article says.
-jim