I go into some detail on this in my paper too.
http://www.lns.com/papers/part15/
Tim
On Fri, Nov 22, 2002 at 12:29:29AM -0500, Jim Thompson wrote:
>
> On Thursday, Nov 21, 2002, at 19:20 US/Eastern, Tim Pozar wrote:
>
> > Of course at 5.8 GHz there are different restrictions on power.
>
> At 5.8GHz, TX power is still limited to 1W (30dBm), and if you're
> running
> PTP under the UNII rules, you get 23dBi of gain before you start a 1:1
> reduction
> in dBm for every dBi of antenna gain over 23dBi, while if you're running
> PTP the ISM rules, antenna gain is unlimited. Relevant sections
> quoted:
>
> 47CFR15.247:
> 2)
> (b) The maximum peak output power of the intentional radiator shall
> not exceed the following:
> (1) For frequency hopping systems in the 2400-2483.5 MHz band
> employing at least 75 hopping channels, all frequency hopping systems in
> the 5725-5850 MHz band, and all direct sequence systems: 1 watt.
> [...]
> (3) 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.
> (i) Systems operating in the 2400-2483.5 MHz band that are used
> exclusively for fixed, point-to-point operations may employ transmitting
> antennas with directional gain greater than 6 dBi provided the maximum
> peak output power of the intentional radiator is reduced by 1 dB for
> every 3 dB that the directional gain of the antenna exceeds 6 dBi.
> (ii) Systems operating in the 5725-5850 MHz band that are used
> exclusively for fixed, point-to-point operations may employ transmitting
> antennas with directional gain greater than 6 dBi without any
> corresponding reduction in transmitter peak output power.
>
> 47CFR15.407
> (a) Power limits:
> (3) For the band 5.725-5.825 GHz, the peak transmit power over the
> frequency band of operation shall not exceed the lesser of 1 W or 17 dBm
> + 10logB, where B is the 26-dB emission bandwidth in MHz. In addition,
> the peak power spectral density shall not exceed 17 dBm in any 1-MHz
> band. If transmitting antennas of directional gain greater than 6 dBi
> are used, both the peak transmit power and the peak power spectral
> density shall be reduced by the amount in dB that the directional gain
> of the antenna exceeds 6 dBi. However, fixed point-to-point U-NII
> devices operating in this band may employ transmitting antennas with
> directional gain up to 23 dBi without any corresponding reduction in the
> transmitter peak output power or peak power spectral density. For fixed,
> point-to-point U-NII transmitters that employ a directional antenna gain
> greater than 23 dBi, a 1 dB reduction in peak transmitter power and peak
> power spectral density for each 1 dB of antenna gain in excess of 23 dBi
> would be required. Fixed, point-to-point operations exclude the use of
> point-to-multipoint systems, omni directional applications, and multiple
> collocated transmitters transmitting the same information. The operator
> of the U-NII device, or if the equipment is professionally installed,
> the installer, is responsible for ensuring that systems employing high
> gain directional antennas are used exclusively for fixed, point-to-point
> operations.
--
Snail: Tim Pozar / LNS / 1978 45th Ave / San Francisco CA 94116 / USA
POTS: +1 415 665 3790 Radio: KC6GNJ / KAE6247
"A mass in movement resists change of direction. So does the world
oppose a new idea. It takes time to make up the minds to its value
and importance. Ignorance, prejudice and inertia of the old retard
its early progress. It is discredited by insincere exponents and
selfish exploiters. It is attacked and condemned by its enemies.
Eventually, though, all barriers are thrown down, and it spreads
like fire. This will also prove true of the wireless art."
- Nikola Tesla in 1908
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