Antenna thought (polarization)

Slashhax0r · 01-04-2003

Hey fellow wardrivers.

While I started my wardriving efforts in
our little city, It suddenly dawned upon me,
is there a standard for polarization for antennas
for 802.11? My wap is vertical, the laptop is horizontal...
supposedly from what I remember there is a 20db loss
when you try to talk to a station that's the opposite polarization
as you..

Perhaps we should be looking at helical antennas, or even
just throwing a vertical whip and a horizontal whip on a splitter...

Ahh.. just a thought.

any of you folks building antennas?

VE6KLJ

db8tr · 01-04-2003

I too have thought about polarization, and from looking at most of the access points on the market, it seems that the vast majority are vertically polarized. For those with moveable antennas, most non-technical people would probably point them up thinking of that orientation would naturally provide the best performance. My AP has a diversity antenna system, and I have one antenna horizontal and one vertical. So wherever I am in the house, I still get the benefits from correct polarization. I have been looking into a helical antenna though. I found a promising design at: http://helix.remco.tk/ . Having said all this, I have not done any testing... either qualitative or quantitative, to figure out how much polarization affects signal strength at 2.4gHz. I suppose that a little googling might provide an answer.

Thorn · 01-04-2003

You're right Slashhax0r, the standard seems to be vertical for the APs, and horizontal for the cards. I don't recall if it's a 20dB difference, but you can see it on a client's signal meter just by rotating a laptop 90º on the long axis. Of course, getting that great signal has it's price, as typing becomes a real bitch.

A couple of people have discussed helicals, although I don't recall anyone actually using one.

And yes, a fair amount of people have built their own. Take a look here: http://forums.netstumbler.com/showth...&threadid=2034 Other threads about this abound. Search on "homebrew" and you'll get quite a few.

Of course, the knowledge of the forum members varies from "why won't tv coax work" to people using sophisticated antenna modeling programs, so you'll see a wide variety in skills and understanding.

Slashhax0r · 01-04-2003

Quote:

You're right Slashhax0r, the standard seems to be vertical for the APs, and horizontal for the cards. I don't recall if it's a 20dB difference, but you can see it on a client's signal meter just by rotating a laptop 90º on the long axis. Of course, getting that great signal has it's price, as typing becomes a real bitch.

Hehe. I thought so, I'm a ham radio operator, so i've built my share of antennas, although amongst the hams in my area there seems to be a fear of 2 ghz stuff!

I think that even just using a vertical and horizontal whip with a phasing harness would be a slight improvement.. I'll have to start
digging through my ham antenna books.

Slashhax0r · 01-04-2003

Quote:

Originally posted by db8tr
I too have thought about polarization, and from looking at most of the access points on the market, it seems that the vast majority are vertically polarized. For those with moveable antennas, most non-technical people would probably point them up thinking of that orientation would naturally provide the best performance. My AP has a diversity antenna system, and I have one antenna horizontal and one vertical. So wherever I am in the house, I still get the benefits from correct polarization. I have been looking into a helical antenna though. I found a promising design at: http://helix.remco.tk/ . Having said all this, I have not done any testing... either qualitative or quantitative, to figure out how much polarization affects signal strength at 2.4gHz. I suppose that a little googling might provide an answer.

My AP is the same, its got the two whips.. perhaps this is a solution to another problem at work, out AP has kinda sissy range, I think the difference between polarizations has something to go with it.

Thanks for the info..

It's kinda funny how I totally wasn't applying my ham knowledge to this, just because it's 802.11 Hah.. I'll have my ap all tuned up and with external antennas (on my balcony) in no time.

01-04-2003	#1 (permalink)
Slashhax0r Registered Member Join Date: Dec 2002 Posts: 7	Antenna thought (polarization) Hey fellow wardrivers. While I started my wardriving efforts in our little city, It suddenly dawned upon me, is there a standard for polarization for antennas for 802.11? My wap is vertical, the laptop is horizontal... supposedly from what I remember there is a 20db loss when you try to talk to a station that's the opposite polarization as you.. Perhaps we should be looking at helical antennas, or even just throwing a vertical whip and a horizontal whip on a splitter... Ahh.. just a thought. any of you folks building antennas? VE6KLJ

01-04-2003	#2 (permalink)
db8tr Wireless Widget Whacker Join Date: May 2002 Location: Kansas Posts: 145	I too have thought about polarization, and from looking at most of the access points on the market, it seems that the vast majority are vertically polarized. For those with moveable antennas, most non-technical people would probably point them up thinking of that orientation would naturally provide the best performance. My AP has a diversity antenna system, and I have one antenna horizontal and one vertical. So wherever I am in the house, I still get the benefits from correct polarization. I have been looking into a helical antenna though. I found a promising design at: http://helix.remco.tk/ . Having said all this, I have not done any testing... either qualitative or quantitative, to figure out how much polarization affects signal strength at 2.4gHz. I suppose that a little googling might provide an answer. __________________ -Db8tr

01-04-2003	#3 (permalink)
Thorn Did you do the math? Join Date: Apr 2002 Location: Villa Straylight Posts: 10,358	You're right Slashhax0r, the standard seems to be vertical for the APs, and horizontal for the cards. I don't recall if it's a 20dB difference, but you can see it on a client's signal meter just by rotating a laptop 90º on the long axis. Of course, getting that great signal has it's price, as typing becomes a real bitch. A couple of people have discussed helicals, although I don't recall anyone actually using one. And yes, a fair amount of people have built their own. Take a look here: http://forums.netstumbler.com/showth...&threadid=2034 Other threads about this abound. Search on "homebrew" and you'll get quite a few. Of course, the knowledge of the forum members varies from "why won't tv coax work" to people using sophisticated antenna modeling programs, so you'll see a wide variety in skills and understanding. __________________ Thorn "Read Altas Shrugged. Compare it to today. Repeat as necessary"

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