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russotto
join:2000-10-05
West Orange, NJ

russotto to shoe1

Member

to shoe1

Re: 10-15 mile Wifi possible cheap? legal?

said by shoe1:

So a Linksys WRT54GL(2.4ghz) with 100mW output with a 24dBm yagi antenna would be illegal? When raising the power output on routers with dd-wrt is heat the only issue? I can install extra cooling if need be, but will the router mess up for other reasons? When does too much power start affecting things?(preferably in the WRT54GL)

I can't figure your formulas for finding how much mW translated to dBm, could you explain that a little bit more?
1 mW = 0 dBm (this is part of the definition of dBm)
10 mW = 10 dBm
100 mW = 20 dBm
1000 mW = 1 W = 30 dBm
10000 mw = 10 W = 40 dBm

Your antenna is not 24dBm. It is 24dBi, where the "i" means that the reference (0dBi) is a theoretical perfect isotropic radiator (an antenna which radiates equally in all directions)

You can add those figures to get effective isotropic radiated power -- 20 dBm + 24 dBi = 44 dBm EIRP. This is well above the legal limit of 4W (about 36 dBm)
LLigetfa
join:2006-05-15
Fort Frances, ON

LLigetfa

Member

said by russotto:

This is well above the legal limit of 4W (about 36 dBm)
Depends...
In the context of a Linksys, we are talking about 2.4GHz band which for PtP allows heigher EIRP. The 36dBm limit is for PtMP and even then, only for the AP. The clients are allowed the PtP exception.
stevech0
join:2006-09-17
San Diego, CA

stevech0

Member

I should re-check, but as I recall 4W is the US FCC limit for point-to-point with about 10 degree H beamwidth. Point to multipoint was far less. But my memory may be at fault.

And the FCC regs I recall do not distinguish between a client and an access point. From an FCC viewpoint, they're all radios and can interfere.

Killer Max
@rr.com

Killer Max

Anon

said by stevech0:

I should re-check...
Don't ! This thread is much more interesting with all the speculation going on.
LLigetfa
join:2006-05-15
Fort Frances, ON

LLigetfa

Member

said by Killer Max :
said by stevech0:

I should re-check...
Don't ! This thread is much more interesting with all the speculation going on.
LOL
SteveO just loves to challenge everything I say and you want to take his fun away?

Of course I have to go by IC rules despite the fact I can throw a stone across the river onto US soil but I am quite confident in my knowledge of FCC rules even though they don't apply to me. You'd think that Americans would know their own rules better than Canadians.
stevech0
join:2006-09-17
San Diego, CA

2 edits

stevech0

Member

FCC 15.247(b)(3)
for 2.4GHz, the transmitter power must reduce by 1dB for every 3dB of antenna gain in excess of 6dBi.

Also, freq. hopping system have more stringent power limits. At 2.4GHz, this is mostly Bluetooth these days.

Interesting that this is NOT required in the 5.8GHz band.

------------
What I do know about the US FCC is that they have taken in many BILLIONS of DOLLARS in the spectrum auctions. That's where they sell the ether that nature and God gave us.
LLigetfa
join:2006-05-15
Fort Frances, ON

LLigetfa

Member

Ain't that the truth.

Here is the IC prayer book that I follow.
»strategis.ic.gc.ca/epic/ ··· 210e.pdf

For a quick lookup of FCC stuff however, I often refer to the Telex FAQ.
»www.telexwireless.com/FA ··· rketID=1
LLigetfa

LLigetfa to stevech0

Member

to stevech0
Click for full size
BTW, here is a view through one of my IP cameras aimed South. The lights on the other side of the river is US soil. That thing in the foreground is a hydraulic truck dumper. It picks up giant B trains and stands them on end, dumping out the wood chips. The construction equipment is a second dumper being built.
stevech0
join:2006-09-17
San Diego, CA

stevech0

Member

I was on a project in NYC where we ran wire mesh parabolic dishes, 802.11a 5.8GHz, and had 10 or so near line of sight links, some of which were 5-10 miles. Two used high gain omni's that provided service on the across the river between Manhattan and NJ, and ashore in NYC for a half mile or so to rooftops.