Subject: [NEXTEL-1] FCC Allows Add-on Antennas But Read the Fine Print

From: [email-masked]
Date: Wed, 28 Jul 2004 15:54:37 -0400

July 23, 2004

FCC Allows Add-on Antennas But Read the Fine Print

FCC rule allows end-users to change out antennas on their Wi-Fi and
other gear legally if the manufacturer has performed the right tests and
the antennas conform to certain guidelines: Jim Thompson alerted me to
FCC rule 04-165 issued July 12, 2004, which has some substantial changes
for devices that use unlicensed spectrum, most significantly Wi-Fi. The
rules affect devices that operate under Part 2 and Part 15 rules, and
we’re most concerned with Part 15, which governs 900 MHz, 2.4 GHz, and
several bands in 5 GHz.

The most notable general applicable of this rule change is in section 2,
which starts with point 18: “Replacement Antennas for Unlicensed
Devices.” Until now, the FCC has required that any antenna to be used
with a device operating under Part 15 rules had to be tested and
certified as part of a system. There was no mix and match proviso.
Further, the FCC required unique connectors for each manufacturer, and
required new connectors to be designed as the existing ones became
commonplace.
“Wait,” you may ask—“I can go to HyperLink Technologies or other
companies and buy antennas with the right connectors and attach them to
my Wi-Fi gateway. If it’s illegal, how can I buy this gear?” Simple.
It’s legal to sell antennas; it’s illegal to use them. It’s the same
logic that guides the sale of bongs and switchblade kits. It’s opposite
to the logic that underlies the Digital Millennium Copyright Act. The
antenna/switchblade law essentially says that the seller isn’t
responsible for all the uses to which a purchaser may put a product. The
purchaser is obliged to know local and federal rules and conform to
them.
Thus, attach the antenna, and you’re a pirate. Assemble the switchblade,
and you’re a criminal. Forget that there have been approximately zero
prosecutions for the use of these antennas on home or business systems.
But no one wants to be in de facto violation of a law, especially
businesses that may considering building out Wi-Fi as part of their
operations. The lawyers might look askance, and the companies might have
to pay enormously higher fees to purchase legal antennas—if they’re
available.  Those fees help cover the companies’ cost in certifying the
antennas as part of a system, but also represent their lock-in market
for legal use.

The FCC rule doesn’t suddenly make all antennas legal for all systems.
Instead, they have chosen a clever middle ground. For new devices—or,
presumably for recertification of old devices—manufacturers will be
allowed to test the system with high-gain antennas of each major type,
like omni, patch, yagi, and so forth. Once the device is certified, the
manufacturer can release the characteristics of the antennas they tested
for both their in-band and out-of-band signal patterns and strengths.
(Out-of-band transmissions are the inevitable but not intentional
frequencies that are broadcast on at typically very low levels due to
harmonics and other technical radio issues.)

Thus, if Linksys certifies its WRT54G with a very high-gain yagi antenna
within the Part 15 rules, then a user can add a lower-gain yagi that has
all its parameters within those levels and be perfectly legal.

Jim Thompson provided a longer, detailed explanation via email:

“Let’s say you have a (warning, plug alert!) HS3000 that has been tested
with a 9dBi omni. Were you to find an 8dBi omni from a different
manufacturer, with similar out of band gain (i.e. it doesn’t generate
more gain in the restricted bands, thereby causing a system that would
otherwise comply with the restricted band limits to ‘go illegal’), you
could use it.

“You could also attach a 2.2dBi omni, as long as it didn’t have more
gain out of band than the antennas with which the device is certified.
You can repeat the above paragraph substituting ‘yagi’ or ‘patch’ or
‘grid’ antenna everywhere ‘omni’ occurs.
“What you can’t do is certify (let’s say) with a single 2.2dBi omni, and
then have your customer attach a 13dBi yagi, (without recertification),
nor could you say, certify with a 13dBi yagi and have your customer
attach a 13dBi patch (or omni).”
I have some suspicion that the recent array of Linksys add-on antennas
were certified under this new rule and delayed for release until such
point that the rule could go into effect. This rule would dramatically
reduce the cost of re-certifying gear for more antennas, and it makes it
possible for Linksys to sell a huge matrix of their own antennas at no
additional testing cost beyond the initial certification. On the other
hand, it also makes it easier for third parties to sell antennas legally
for Linksys’s devices, but sales of legal antennas for illegal uses has
seemed to curtail sales before this.

Remember that until a device is retested under these rules—and who knows
if manufacturers will pay to retest the current generation of
equipment—you’re still technically violating the law by mixing and
matching antennas. Watch for more news on this front, as devices are
certified until these new rules.

The FCC decided to leave the connector rules intact, even though
manufacturers argued that it’s so easy to get their “proprietary”
connectors from third parties, that the current rules just added cost
and complexity. The FCC demurred, noting that it wanted to make it just
hard enough to make adding an antenna an intentional act. It gets lost
in the furor over unscientific concerns about the risk of Wi-Fi and 2.4
GHz electromagnetic radiation that microwaves can injure humans at
sufficiently high gain—far, far higher than the Part 15 rules allow.

The FCC said in regards to the connector issue, “…our concern that
removing this requirement might have the unintended consequence of
allowing uninformed consumers to inadvertently attach an antenna which
causes the device to emit at levels in excess of the limits for human
exposure to radio emissions.” Good enough. It preserves the market for
pigtails, that’s for sure.

This section also revises the rules about integral antennas for 5 GHz
(802.11a and other uses) devices. The FCC will now allow externally
detachable antennas for these devices, which adds flexibility.

The FCC tweaked a number of other rules, including one that appears to
reflect a change in thinking from its one-off approval of Vivato’s
beam-focused Wi-Fi—I’m trying to better understand that section. In
another part, they tweak measurement standards. Part 5 covers changing
rules for frequency hopping to make it possible for future Bluetooth
flavors to work legally in the U.S.

Interestingly, spectrum etiquette in unlicensed bands was discussed in
part 6, but the FCC declined to take any action. They gave props to
Microsoft for a proposal they might implement in the future that would
reduce the noise of devices that aren’t actively transmitting. Some of
these principles are already embodied in 802.11h, which was a required
extension for 802.11a to operate in the 5 GHz band in Europe.
http://wifinetnews.com/

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