[TriLUG] Wireless access
reginald at cisco.com
Tue Sep 23 10:50:15 EDT 2003
If you are doing point to point over a long distance with clear line of
sight, I'd use something more directional than a Yagi. I'd use a
> -----Original Message-----
> From: trilug-bounces at trilug.org
> [mailto:trilug-bounces at trilug.org] On Behalf Of Ron Joffe
> Sent: Tuesday, September 23, 2003 10:24 AM
> To: Triangle Linux Users Group discussion list
> Subject: Re: [TriLUG] Wireless access
> On Tuesday 23 September 2003 10:10 am, Ron Joffe wrote:
> > On Tuesday 23 September 2003 09:19 am, Ralph Blach wrote:
> > > your yaggi might be able to get the Job done, but it would most
> > > assuredly violate the FCC rules. Remeber, that these radio's
> > > operate in the 2.4 ghz ham band and are Secondary users.
> That means
> > > that you will have to put up with Ham activities causing
> > > interference.
> > Would hooking up a Yaggi antenna directly to a commercial 802.11
> > broadband bridge without amplification violate any FCC Rules?
> > Ron
> Well I answered my own question. In the cisco link that Reginald sent:
" In Point-to-Multipoint systems, the FCC has limited the maximum EIRP
(effective isotropic radiated power) to 36dBm. EIRP = TX power + antenna
gain. For every dB that the transmitter power is reduced, the antenna
increased by 1dB. (29dBm TX, +7dB antenna = 36dBm EIRP, 28dBm TX, +8dB
antenna = 36dBm EIRP).
The Cisco Aironet Bridge transmitter power is 20dBm, which is 10dBm
than maximum. This then allows the use of antennas up to 10dB over the
initial 6dBi limit, or 16dBi.
In Point-to-Point systems for 2.4GHz systems, using directional
rules have changed. Because a high gain antenna has a narrow beamwidth,
therefore the likelihood is high that it will cause interference to
area users. Under the rule change, for every dB the transmitter is
below 30dBm, the antenna may be increased from the initial 6dBi, by 3dB.
(29dB Transmitter means 9dBi antenna, 28dB transmitter means 12dBi
Because we are operating at 20dBm, which is 10dB below the 30dBm level,
can increase the out antenna by 30dB. However Cisco has never tested,
therefore is not certified with any antenna larger than 21dBi."
So I read this to mean that using a cisco aironet bridge, I should be
legally use up to a 36dbi Yaggi antenna.
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