Calculating Output Power / Effective Isotropic Radiated Power

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diebaas

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HI Guys,

Thought this might be an iteresting one, all the wifi specialist out there post you comments on how the do the calculations and where to look on the equipment for the details, so that you can teach others the basics of WIFI, and to try and make unsuspecting patrons aware of their wrongfull actions.
 
teaching peoples how to calculate the outpower so that it doesn't go over our legal limit of 100mw and cause exstra noise in the 2.4 or 5.8ghz spectrum
 
diebaas said:
teaching peoples how to calculate the outpower so that it doesn't go over our legal limit of 100mw and cause exstra noise in the 2.4 or 5.8ghz spectrum
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Your best bet would be to buy ICASA certified equipment. No need to do any calculations IMO
 
acidrain said:
afaik mikrotik is not icasa certified, which is bs since imo mikrotik is one of the best if not the best.
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The routerboards isn't, but i know some of the radios is well. Like the CM9, they are certified by icasa, and in my opinion thats what count, cause that is what determine the output power.
 
Only the radio needs to be ICASA certified, because thats the part thats communicating.
 
EIRP (Effective Isotropic Radiated Power) is used around the world to regulate RF systems - simply: Radio Output Power - LESS any losses through cable & connectors PLUS the gain of the antenna.
The common base for these calculations is the dB - where 20 dB = 100mWatt. An increase of 3 dB doubles the mWatt and vice versa. It follows that 23dB = 200mW, 26dB = 400mW etc.
ICASA Type Approval only applies to the active RF components, ie the Access Point, Client Bridge or Mini-PCI card used on MikroTik. MikroTik is "only" the software to provide management features over 802.11 WiFi products. There is a large selection of Type Approved products available locally.
EIRP limits are 20dB(100mW) in 2.4GHz and 30dB(1 Watt) in 5.8GHz.
 
Bertus said:
EIRP limits are 20dB(100mW) in 2.4GHz and 30dB(1 Watt) in 5.8GHz.
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EIRP limits for wireless LAN equipment are:

2400MHz to 2483.5MHz = 100mW (20dBm)
5150MHz to 5350MHz = 200mW (23dBm) indoor use only
5470MHz to 5725MHz = 1W (30dBm) indoor and outdoor use

The band 5725MHz to 5875MHz is only approved for non-specific SRD use, not WLAN, and is limited to 25mW (14dBm) EIRP. Road transport and traffic telematics (RTTT) has a sub-band allocation in that range and can operate up to 2W (33dBm) EIRP between 5795MHz and 5815MHz.

(Sources: Notice 533 of 2004 and Notice 1114 of 2007)

*Trybble
 
There we go, stick to that values and forget about the amps and you are safe.com

If you can do 15-25km with a 31dbi 5.8 grid coupled to a cm9 and connect to a sector with a cm9 and have a signal of -72, who the fook needs amps.
 
Nice theory, nOss, except your numbers don't quite work out. Ignoring for the moment the small fact that 5.8GHz isn't currently available for WLAN use without a spectrum licence, if the CM9's output is 20dBm (100mW) and you put a 31dBi grid on it, that gives you an EIRP of 51dBm, 125892mW or close to 126 Watts! Even being nice and factoring in 4dB loss for 10m of LMR-400 and connectors, you've still got 50118mW (50.1 W) EIRP.

That's *way* over the "speed limit" :)

*Trybble
 
Hold on, so what you're saying is....My Grid isnt an antenna? It's an amp? how the hell can you get to 126Watts with only a 40W power supply running the RB????

Calculate again please.

Also, isnt the dbi rating of the grid more to do with the sensitivity of the grid and less with the power rating?
 
I think I see your problem... Are you using a calculator??? In that case, please but the minus in front of your dbi ratings. Its signal LOSS, not signal AMPING
 
A grid is a passive trasmitter/receiver. There is no way that a grid can amplify the power output of the radio card. And also: the 2 unlicensed ISM bands are 2.4 and 5.8 Ghz, so you do not need a license to use 5.8 Ghz
 
Trybble said:
Nice theory, nOss, except your numbers don't quite work out. Ignoring for the moment the small fact that 5.8GHz isn't currently available for WLAN use without a spectrum licence, if the CM9's output is 20dBm (100mW) and you put a 31dBi grid on it, that gives you an EIRP of 51dBm, 125892mW or close to 126 Watts! Even being nice and factoring in 4dB loss for 10m of LMR-400 and connectors, you've still got 50118mW (50.1 W) EIRP.

That's *way* over the "speed limit" :)

*Trybble
Click to expand...

ZOMG, If this is true does that mean you are not allowed to have any gain on your antenna? If that is the case I don't know of anyone that is legally using a WLAN.

5.8GHz isn't currently available for WLAN use!?

/me runs to go take down his equipment before he ends up in jail!
 
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