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* Safety and Power Emissions [1]
* I fell off the roof of my home after installing an antenna, and I
need someone to sue. Who runs this group, and who insures it? [2]
* Is 2.4Ghz radiation safe? I\'ve heard it uses the same radiation
as my microwave oven? Are you killing me and my chances to reproduce?
[3]
* Someone mentioned 4w is the max power output allowed. I want "more
power" and I\'m willing to spend some serious money to boost my signal
(and to microwave my neighbours, the people who live in a 10km radius
and the surrounding wildlife). [4]
* How do I do this? Whats the deal with EIRP? [5]
* How do I work out my EIRP then? [6]
-------------------------
SAFETY AND POWER EMISSIONS
What's safe and what's not? If your question is not here, try looking
through all of the questions which are listed on TheEvolvingFAQ [7].
I FELL OFF THE ROOF OF MY HOME AFTER INSTALLING AN ANTENNA, AND I NEED
SOMEONE TO SUE. WHO RUNS THIS GROUP, AND WHO INSURES IT?
We are (almost certainly) not liable, but if you feel we are contact
the Committee [8].
-------------------------
IS 2.4GHZ RADIATION SAFE? I\'VE HEARD IT USES THE SAME RADIATION AS MY
MICROWAVE OVEN? ARE YOU KILLING ME AND MY CHANCES TO REPRODUCE?
2.4Ghz signals used for 802.11b/g are limited by law to a maximum
total output of 4W EIRP [9] this is far lower then a microwave oven by
over three orders of magnitude. Even high output cards only put out
200mw (milli-watts) of power, and thus need an antenna to hit the
legal limit.
The WirelessHealth [10] page is a collection of links aimed at
promoting a better understanding of Radio Frequency Electro Magnetic
Radiation (RF and EMR) and the known health risks.
-------------------------
SOMEONE MENTIONED 4W IS THE MAX POWER OUTPUT ALLOWED. I WANT "MORE
POWER" AND I\'M WILLING TO SPEND SOME SERIOUS MONEY TO BOOST MY SIGNAL
(AND TO MICROWAVE MY NEIGHBOURS, THE PEOPLE WHO LIVE IN A 10KM RADIUS
AND THE SURROUNDING WILDLIFE).
YOU WILL BE BREAKING AUSTRALIAN COMUNICATIONS LAW AND WILL BE LIABLE
FOR A VERY LARGE FINE.
We have links over 50KM that are legal, and we can say from
experience that latency at distances above 50km causes serious
problems. Even if you could push the radio signal for 500KM, the link
would be unusable.
-------------------------
HOW DO I DO THIS? WHATS THE DEAL WITH EIRP?
Well, EIRP [11] stands for Emission of Isotropic Radiated Power. The
limit for 802.11b compliance in America, and also in Australia, is 4W
EIRP. In terms of signal output power, that's 36dBm.
The output power for a Lucent/Orinoco/Agere/Avaya 802.11b PC card is
15 dBm. If there is no external antenna then that's the answer. 15dbm.
This is also labelled as 30mw power output. There are some devices
with 100mw and 200mw output, but there is no benefit to performance
unless youre trying to achieve massive distances in a crowded area
with poor antennae.
If you're trying to overcome a problem with a long-distance link,
first get bigger antennae, check the link for obstructions and faults
with equipment, experiment with warping space/time, or move to a
different radio spectrum/channel, before you think about upgrading to
a more powerful device.
If you attach a 2.4ghz amplifier, you need to be careful that the
rated output power does not go over the 36dBm limit once you attach an
antenna and a low-loss cable to the amplifier. See the next question
for details on how to check this.
'NB' adding an amplifier to an 802.11b card will almost certainly be
illegal, as it contravenes the class license on the device.
-------------------------
HOW DO I WORK OUT MY EIRP THEN?
Example: we have a PC Card with a 14 dBi external antenna (a modded
galaxy antenna) and 50 ft (12.7 Metres) of LMR400. we make the
assumptions that the total loss for a pigtail adapter is 0.5 dB and
the loss for each connector on LMR400 is 0.5 dB.
using a quick formula, here's how we work out the EIRP:
PC card - pigtail adapter - connector - 50 ft (12m) of LMR400 -
connector + 14 dBi antenna = ? dB of Total output power
15 dBm - 0.5 dB - 0.5dB - 3.3 dB - 0.5 dB + 14 dBi = 24.7 dBm
The maximum is 36dBm, which makes 4W EIRP.
the resulting signal is roughly 10x stronger than what comes out of
the wireless card, and within the safe limits of the EIRP restriction,
which is 120x the output power of the card.
For more information on working with decibels (dB), and some lookup
tables, check out PowerAndGainToDecibels [12]
-------------------------
CAN\'T FIND THE ANSWERS TO YOUR QUESTIONS? Try looking through all of
the questions listed on TheEvolvingFAQ [13]. If you still can't find
answers, ask your questions here [14].
Links:
------
[1] http://melbournewireless.org.au/#safety_and_power_emissions
[2]
http://melbournewireless.org.au/#i_fell_off_the_roof_of_my_home_after_installing_an_antennaand_i_need_someone_to_suewho_runs_this_group__and_who_insures_it_
[3]
http://melbournewireless.org.au/#is_2_4ghz_radiation_safei_ve_heard_it_uses_the_same_radiation_as_my_microwave_ovenare_you_killing_me_and_my_chances_to_reproduce_
[4]
http://melbournewireless.org.au/#someone_mentioned_4w_is_the_max_power_output_allowedi_wantmore_powerand_i_m_willing_to_spend_some_serious_money_to_boost_my_signaland_to_microwave_my_neighboursthe_people_who_live_in_a_10km_radius_and_the_surrounding_wildlife
[5]
http://melbournewireless.org.au/#how_do_i_do_this___whats_the_deal_with_eirp_
[6] http://melbournewireless.org.au/#how_do_i_work_out_my_eirp_then_
[7] http://melbournewireless.org.au/?TheEvolvingFAQ
[8] http://melbournewireless.org.au/?Committee
[9] http://melbournewireless.org.au/?EIRP
[10] http://melbournewireless.org.au/?WirelessHealth
[11] http://melbournewireless.org.au/?EIRP
[12] http://melbournewireless.org.au/?PowerAndGainToDecibels
[13] http://melbournewireless.org.au/?TheEvolvingFAQ
[14] http://melbournewireless.org.au/?FAQYourAdditions
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