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Hi all ,

I have a question about the 2.4 GHZ wifi frequancy.... why the signal is attenuated while passing through metal , walls , while the cordless phone works on the same range but I can recive signal for long distances.

some times in resorts i can send and recive from a cordless phone 1 kilometer NLOS but for AP HP Colobrous i can't even recive the signal if it pass through 2 walls or 3 walls.

another question is there is any NLOS antenna to cover resorts ... I mean to place the antenna in public areas and to have ac coverage inside the rooms .

That would be because most of those cordless phones are blasting out their signal across a high number of channels without taking into account that other devices are using the frequency. This is why they are particularly destructive to 802.11, they just blast out their signal and have no sense in playing fair with other devices. I would doubt you are getting signal for 1 kilometer, the testing I personally have done with cordless phones has never got to more than about 200 feet from the base station, if that. The basic answer to this, however, is about the power used by the phone and the amount of spectrum it uses in sending its signal.
Of course there are a lot of antenna alternatives you can use to cover public areas of a resort. I have seen myself quite a few places with high power Yagi antennas for example that work well covering the pool and other areas of hotels. Its just a matter of picking one that will cover the area you need.

hi

some times i faced hotel with more than 1000 rooms "[i]in EGYPT there are alot of resorts on huge areas" and I have to cover all the rooms.
structure of rooms , the frontside of rooms m trees , palms and pools are all obstacles that degrade teh signal strength .
I avoid all of that by increasing number of AP , some times I used HP APs dual antenna and repeat them using LINKSYS . but some times it doesn't worth .

any way can you tell me your recommandation about this Antenna.

http://www.wirelessnetworkproducts.com/hd21882.aspx

thanks

Um, this really isn't a good way to go about designing a wireless network. Its not so simple as just 'buy an antenna and put it in to cover the whole site'. Wireless is not plug and play. I would highly suggest that you do a site survey, with proper tools, to figure out what will work given the space you are trying to cover. Its like you wouldn't build a house without any plans, so also you can't design a functioning wireless network without a site survey to make a plan for your wireless spectrum, where the signal will go and what kinds of antennas will work for the particular site you are assessing. Wireless 101, do a site survey FIRST. Especially in a huge resort area.

ok , always I do the site survey .. but due to Time , cost that availabe for me I do Predective site survey .
So the question now if I am in the site "let's say huge resort , narrow windows for the rooms that signal can access , a lot of trees" what's the tools that I can used to do that .

here is a sample for one site
http://www6.0zz0.com/2010/05/08/17/660196140.jpg

http://www6.0zz0.com/2010/05/08/17/456702376.jpg

Well, I can see the problem. I would approach it in two parts. Do a predictive (which will be based on standard omni, I haven't seen any predictive software that handles directional antennas all that well) for the rooms and internal spaces, then you will need a site visit with a couple of different antennas to test the outdoor areas. I normally try to have a 4dBi, 6dbI and 10dBi antenna to use to test placements. This will cut down your on site time and of course your cost. I don't think you can easily do predictive surveys for this kind of outdoor environment, just too many variables that that software can't account for but you as the engineer can.
As to tools, I would suggest Ekahau, LAN Planner (Motorola) or Air Magnet Survey.

I would be a little suspicious of that antenna you are looking at. The site itself may be legitimate, and actually sell you what you order, but they look like they try to sell everything they can get their hands on, without making any real attempt to qualify/quantify what they are selling.

Their claims for this antenna seem very vague, and at the same time too good to be true. The socalled spec page is absent of very much real data.

Take a look at http://www.tessco.com/ to see what a truly legitimate antenna web site looks like. And there are many others too of course.

You know what they say - if it sounds too good to be true, it probably is.

Besides that, the few specs it does quote don't look to me like one you would want for your application.

Another thing as far as I am aware is that the antenna has to have been tested with the access point by the manufacturer to be a correct impementation in line with the regulatory domain specifications. Adding antennas from various manufaturers is fraught with issues.

Pete,

You are right. I know the FCC loosened up their requirements for antennas a couple years ago, but I have no idea what say the EU or Japan, might allow.

We can find out their channel usage fairly easy, but I've never seen an "antenna connections by country" list.

I know many countries follow FCC rulings, but I can't tell you which ones off the top of my head.

I think everyone is pretty relaxed about it, I have never had any issues or the wireless police coming around however I tend to stick with vendor recommended antennas and buy from the vendor, wether that HP, Aruba or Cisco because of 2 points

1 Warranty

2 Wiireless police, or rather a validated solution

I know generally it doesnt make a huge difference but its not unknown to take an antenna apart and find nothing in it!! Allegedly