Wifi Legal power limit help!!

[AntiMiracleMan]

Goodmorning.

I am trying a painfull project that no one can shine some light on atm...
I have a router in my roof with a wifi network that i want people around me to connect to for some gaming.
its the normal old telkom router with the zcon mini pci wifi card in... producing 50mW or 17dBm of power...

I then built a biquad (directional aerial) with about 10dBi gain... first site of client to connect to my router is about
250M away with a few tree branches in the way... Picked up signal but then it dropped the whole time etc etc.. Now that is a nice distance for 50mW... Heres my question...

What is the legal limit of dBm and mW that we can use... I was looking online and people are buying these wifi antenna boosters working at 2000mW or 33dBm. and with a normal 5dBi antenna on it... Isant that illegal...
http://www.pricecheck.co.za/offers/34019535/EP-WB2000+New+2000mW+2W+2.4GHz+802.11b_g+WLAN+Wireless+Signal+Amplifier+Power+Wifi+Booster/

Thats the boosters i see all over.. Now i dont just wanna run my 17dBm router into this 33dbm booster and add a 5dbi antenna... this sounds way over the top... (not taking into account loss of signal with joins and cable)

So A: Would i be in trouble with a device freely sold in sa and online, and what is SA legal limit ?
B: Amplifiers also amplify noise, how would you go about boosting the low 50mW and 17dBm wifi router, with amplifier or just with antenna?

Thanks alot for any responce as it became a bit of a headache allready....

Francois

 

[AntiMiracleMan]

PS: This is on the normal 2.4ghz range

 

[dadecoza]

afaik the legal limit is 100mw (the law is not very clear on if this is after or before antenna gain). Anyways I would rather get a propper out door router like a bullet2 (okay the wuggers will laugh at me for calling a bullet2 propper but in your case we will keep it simple) and a 12dbi omni antenna (now I will get in trouble for mentioning omnis) the setup should cost you less then a R1000.

What will your clients have on their side?

I'm sharing internet with my neighbours (zomg) with a bullet and omni some of them sommer connect directly with their laptops.

If they are all in the same direction you can maybe look at a panel or even sector antenna. no need to go over 100mw as long as there is clear line of sight or they are close enough.

look at http://scoop.co.za/ for wireless awesomeness.

Ps. well done on building a biquad I alos still have one from the early ctwug days

 

[AntiMiracleMan]

hi dade.
Thx for your info... Dont laugh now but client side we are using the wifi dongle in a sif.. Works very well indeed .
Im trying to keep the costs down... so i dont want to change the router... have that allready.. Thats why the idea of the booster amp came into mind... Is this device illegal then ??? They are not in the same direction so thats why i thought of going 5dbi omni directional with a bosster... Rather then a 50mW with a 24dbi directional... if you catch my drift

100mW = 20dBm.. thats kinda stupid as an normal 7dbi antenna mounted to an old telkom router is illegal ??
more commenly on 100mW routers u can add 24dbi antennas and get huge probs there ? Bare in mind i have a router with 50mW i want to use... this is not my internet router and wont allow the clients to even see the inet bridge

 

[FNfal]

AFIK transmitters are rated in watts, miliwatts (power output ) so it dont matter what antennae you put on the end for gain .
For sure a 2 watt linear amplifier will be illegal (wifi antenna boosters working at 2000mW)
http://mybroadband.co.za/news/wireless/7982-are-you-breaking-the-law-with-your-wi-fi-antenna.html

 

[rorz0r]

100mW is the legal limit. Antenna makes no diff.

 

[xumwun]

I'm pretty sure 2000mw is totally overkill for 250m anyway.

 

[AntiMiracleMan]

ye well this is what i was thinking... knowing amplifiers i know that the 2000mW is the peak! Also i know that double the power = 3db.... but thats excluding the cable runs or the input power... so if the amp gives out peak at full power... with a reccommended power input of 100mW... That means my input power is half of what it should be to get the 2000mW...

Had a talk with ICASA just now... regarding this issue.. According to the official i need a licence to run any network in the outside... I ask him to email me the regulation limits and are waiting to get it from him... This makes no sense...

The regulation has a 100mW limit... now you add a 20dBi antenna ad you are over the limit.... Even with only a 100mw..

Is the law on the mW or on the dBm ?

 

[daffy]

Is the law on the mW or on the dBm ?

Its measured on EIRP.
The law in South Africa for 2.4Ghz is 20dBm (or 100mW)

EIRP is calculated as:
Radio TX Power + Antenna Gain - Cable/Connector losses

So a 100mW Radio with a 20dBi antenna and a few connectors work out at

20dB + 20dB - 3dB = 37dB
Which is waaaay over the 20dB EIRP limit (37dB = 5Watts)

http://www.fab-corp.com/pages.php?pageid=1

 

[AntiMiracleMan]

Thx Daffy. I was under the impression that the limit is only on the mW... So this is wat i have decided to do...
I will keep my 17dBm 50mW and gain the losses on a nice areal Not gonna struggle around with the active amplifiers...
I guess im just struggeling to see how people can get these insane distances on some equipment without clearly violating the EIRP law...
Does the WUG's running in SA have licences ? or am i tredding on the rattlesnakes rattle ?

 

[daffy]

Jawug has what is necessary to operate as a Community run, free network, with no internet services provided.

Careful antenna selection is the key to creating long distance links that stay on the correct side of the limitations in law.
If I ever come across a router that is outside of the specs on the Jawug network, I immediately return it to sane settings. This doesn't happen often thankfully, and we encourage and educate our users on this.
Jawug is a member of the ISPA and WAPA, and conforms to the Code of Conduct for both.

Db and mW are both measurements of power, and you can convert between them. But you cannot mix them in the EIRP calculation. Thats like adding apples and pears to figure out how many bananas you have.

 

[AntiMiracleMan]

ye thats what confused me there for a bit.. im a qualified sound engineer and also electrical... so dB i worked with alot... mW i work with alot.. Combining the two in wifi just opened alot of things for me.. Intresting as allways was the 3db rise in double the power.. Really opened my mind to the 50mw being little... its just 3dBm less than a 100 mw.. easly to be gained by the right antenna.

As for EIRP and Icasa... i get the feeling that its still a grey area around this and they can only "act" when they get a complaint etc... which is prob why guys get away with it.

Thanks alot for your info daffy appreciate it

 

[Superspeed]

We manage and run wifi networks all over the country. I have found a few networks that are grossly over the specified max EIRP. ICASA has been notified but never does a thing. My advice - get the strongest antenna you can get an nuke the neighbourhood

 

[acidrain]

I'm actually curious as to whether the legal limits apply anymore as the legal limit for 5Ghz is 1W yet the MT SXT5HP has a 16dbi antenna + a 31dbm card which is well over the 1W limit and is ICASA approved.

 

[AntiMiracleMan]

Ye i noticed the 1W limit on 5ghz... got sent a PDF on the limits by icasa... they were more intrested in my contact details ....
asked them if i need a license to run a normal network between friends... this was a few days ago... no reply... il take it as a no

 

[Diabolix]

On any mikrotik you can set the country, that will ensure that you stay within your countries legal limit.

 

[Hummercellc]

Yes but the Mikrotik device has no idea what antenna you have on it? so will limit on power level only.

 

[AntiMiracleMan]

jip 100mw is 100mw... no officer... dont worry about this big antenna on my roof... its for talking to the aliens!

 

[Diabolix]

Yes but the Mikrotik device has no idea what antenna you have on it? so will limit on power level only.

You can. You can set the dbi antenna you have connected to the radio, and it will limit accordingly.

 

[AntiMiracleMan]

You can. You can set the dbi antenna you have connected to the radio, and it will limit accordingly.

Why would someone use this option... i mean you dont buy a aerial cause you would like to limit the rf on the card just saying i know its illegal but how many people will use it actually?