What is the point of 17 dBi?

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headstrong

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Hi

What is the point of having a 17dBi antenna when I can use an 8 dBi and boost the signal with dd-wrt firmware....?

Is there something I am missing?

Thanks
 
headstrong said:
Hi

What is the point of having a 17dBi antenna when I can use an 8 dBi and boost the signal with dd-wrt firmware....?
Click to expand...

Is there something I am missing?
Click to expand...
Yes.

..:D ok, OK - I'll tell you what: as antennas give you ever more gain they focus to an ever finer degree at the same time. Reason for this is NOTHING for nothing: against the theoretical isotropic reference antenna which radiates perfectly in all directions, as you jack up the gain (dBi number) you take all that radiation and squish it ever tighter in your chosen direction. The GOOD news here is that it's pure, all you're doing is focussing what you already have and aren't messing with it.

But boosting the amp in the router is a WHOLE different animal. Down that road lies all manner of lurgies, notably as you boost your signal you ALSO amplify the noise level. If it helps think of the difference between a GOOD audio amp/speaker cranked to high volume and another one next to it that's gone into distortion ... the latter sounds pretty crap - and that's what you end up with when you jack up an amp.
 
let me add my 2cents...

i've got a 100meter link between 2 sites...

caseA:

it was 2 x 21dbi directional grid antennas on both sides - both with dlink dwl2100AP''s behind each one...thus 28mW amplification..

i could get up to 5.5/6.0MB/sec transfer speed but this was a very unastable link for some reason! - perfect line of sight

superG with static turbo...

caseB:

i replace one side with a linksys CPE (17db panel+wrt54gl(ddwrtsp2)) and jack it up to 100mW...

0 packet loss , and the link is much more stable

only drawback - its 54mips - thus max transfer i can get 3.6-4.0



so i'd say in all that amplification does help...but not like certain retailers who sell 3dbi omni's with 1watt amplification..thats just wrong and bad!

cheers
 
OK that seems to make more sense now.....

Ok heres what I need 2 do:

use a 12 dBi yagi antenna for a link between 2 houses....now as bdt says, the 12dBi yagi will "squish the radiation ever tighter" .....i understand that...hence directional antenna...

but heres what I want 2 do:
use an 8dBi patch antenna and use dd-wrt and boost signal however much so that the output is 12 dBi....

How does noise affect latency and throughput?
Thanks
 
headstrong said:
Hi

What is the point of having a 17dBi antenna when I can use an 8 dBi and boost the signal with dd-wrt firmware....?

Is there something I am missing?

Thanks
Click to expand...

Because increasing the power but keeping a lower gain antenna wont do jack for the received signal only transmitted signal.
 
OK, my post is a cautionary tale on the principles and concepts. At the level you're, well, playing you're FAR from being in any real danger of ending up with a broadband (in the radio sense) noise generator squatting on the neighbourhood ruining Wi-Fi for everyone. Just, with small antennas like this (notably the 8dBi one) you want to avoid long co-ax runs and go for as much height/LOS as you can get.
 
Setsquare said:
wont do jack for the received signal only transmitted signal.
Click to expand...

Why won't it help with the received signal? if use a 8dBi antennas at each end and each with dd-wrt boosting the amp will that help will received and transmitted signal?

Sorry if I ask noob questions!
 
headstrong said:
Why won't it help with the received signal? if use a 8dBi antennas at each end and each with dd-wrt boosting the amp will that help will received and transmitted signal?

Sorry if I ask noob questions!
Click to expand...
Sooner or later EVERYone is a n00b, don't sweat it. As to amping, you boost the signal the device transmits, but you don't jack the sensitivity up along with it.

Except you're looking at this:

[amped 8dBi box] -> boost to get range to reach [std 12dBi box] ..this may be enough to get you the range

[std 12dBi box] -> boost to get range to reach [amped 8dBi box] is a stronger signal from the 12dBi to the weaker receiver - but if you're close enough the 8dBi may be strong enough to pick the signal up anyway.

Caution: just about everyone else here will tell you that this is heresy: use at your own risk, YMMV.
 
headstrong said:
use dd-wrt and boost signal however much so that the output is 12 dBi....
Click to expand...
I assume you using the WRT54GL with this firmaware on it?

Just a word of warning - pushing the output power above 60mW has been known to cook such hardware. I had a WRT54GL running at 40mW and it died recently with symptoms of partially crisped insides... ;)
 
What do u mean it died? did it stop working completely or should very tempremental?
 
What happened once the nvram was corrupted? Coz my wrt54gl with dd-wrt v23sp2 is giving me problems!!!!

I cant connect to any AP in client mode..........is this because of the NVRAM?
 
My wrt is running at 100mw for nearly 7months now and no prob, also using dd-wrt
 
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