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WiFi range experiment, please read and give me some comments

I

iamgenius

Senior member
Okay, I'll soon be working in a place where the only internet source allowed is placed inside a lobby/rest area (whatever you want to call it). And as you might have guessed it is a wireless router. You will have to get in there and connect via WLAN. That's fine, but not good enough for me. I want to be able to use internet from inside my room which is located about 250 meters from the the building containing the router.

I only visited the place for one time, so I wasn't able to investigate further. I know I can use a range extender and place the original router in good places so that I can get a good signal from inside my room, but I actually don't want to do that because it might enable others to connect and suck up the bandwidth which is already low(1Mbs). And please don't think that's selfish because I'll be in charge of stuff that needs internet whereas others will mainly use it for Prosperity.

Anyways, that was an introduction and here is the little experiment I did over the two past days:


Devices used:

1-My HP laptop(Pavillion dv2000)



2-The alfa wireless adapter which is arguably the best wifi adapter out there( I used the 2 watts version, although I don't how that matters for receivers !)



3-My Blackberry bold 9700



Uploaded with ImageShack.us

4-My nokia E52



5-My good old router(the infamous Dlink DIR655 router)



6-New Aztech wireless router provided from my ISP(aztech hw550-3g):



7-Two high gain wifi antennas (shown below):




Of course the purpose of the experiment was to figure out how to get the strongest signal from inside my room. I'll proceed with the experiment findings and details in the next post.
 
I took my laptop with me along with the alfa adapter and one of the two high gain antennas and drove my car and parked my car in a crowded area with many tall buildings surrounding me. And then I began testing. I turned on my laptop and it was able to find about 10 wifi access points using its built-in WLAN card. I did this while inside the car! I opened the windows but that didn't have an impact...I got the almost the same networks.

I then went to see how my nokia phone does. It was able to pick about 3(sometimes 4 signals). Not bad for a little smartphone I guess. Opening the windows didn't affect the nokia's receiving as well.

Then It was my blackberry turn! Amazingly enough, it was able to find about the same number of networks my laptop found and even more when I open the windows. Opening the windows for the blackberry have always increased its receiving performance. I tried this in more than one location! From this alone, I think I can conclude that the blackberry has a well-designed WiFi receiver.

Okay.........the Alfa adapter turn I guess. I disabled my laptop's built in Wlan card and plugged the alfa adapter via USB. And WOW, the alfa with its 5 dbi original antenna was able to find a whopping 43 networks all with fair/good signal. They didn't call it the best for nothing I guess:

http://www.data-alliance.net/-strse-158/Alfa-AWUS036NH-2000mW-1000mW/Detail.bok
.

I love it. It really works, and I was able to connect to some unprotected networks and use the internet from inside my car. Illegal I know, but few minutes for the sake of my experiment is fine I think!

Putting the adapter outside the car didn't really improve performance, although I was expecting the opposite!

Will the alfa enable me to pick the signal coming out of that 250 meters away building? I wonder.

More findings to come. ( Please bear with me, and if you notice something stupid, it is because I'm not a WiFi expert....just a normal user)
 
xSauronx said:
😀
Click to expand...

Think I'm kidding. I've run into this plenty of times before. I due my duty and report their ass to the FCC. You are interfering with my wireless spectrum and I WILL report your ass. The reason why it all works is because there are limits.

An omni with a 2 watt radio is outside EIRP limits.
 
directional +14dbi with 80mw output 802.11b can travel quite a bit of distance.

remember higher symbol rates reduce effective transmission distance unless you are working with a protocol that doesn't mind extremely high packet loss.
 
Okay I'm back.

spidey07, please calm down. This is just an experiment I want to learn from, and it is done in a place thousands of miles away from your location, I assure you. Plus, where I want to implement such a solution is an isolated place. The internet source is an expensive satellite connection(See how isolated the place is?). In addition, the 2 watts device I'm using is a receiver(not a transmitter) sold legally, so why the fuss? And please don't think I'm trying to harm anybody, no bad intentions are involved at all.

And as a last note, why are there directional antennas with really high gain exist?

http://www.radiolabs.com/products/antennas/2.4gig/2.4-aluminum-parabolic.php

I know they are directional, but they can still interfere with other signals, right?

And wait to see my results.
 
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On to the experiment:

It was time to try the super high gain antenna with my alfa and see how that affects things. So, I connected it instead of the original 5 dbi gain and was excited to see the results. To my surprise, no more networks were found. Actually even less sometimes! Putting the antenna on top of my car with its magnetic base produced little more networks. Connecting the antenna directly to the alfa adapter yielded better results than when connecting it with the cable provided, and this is probably because of the signal loss in the cable. I was really disappointed! A much more higher gain antenna gained me nothing at all. But, there must be some good reason for that. I think the alfa with its original 5 dbi antenna was already picking up most if not all wifi access points in the area, or maybe the 13 dbi antenna is not fully compatible with my alfa. There is an alfa version that comes with a 9 dbi antenna instead of the five. I wonder if that would have changed anything at all.
 
I figured high gain antennas are really for wireless routers, and not for receivers, so I convinced myself my high gain antenna will do wonders when connected to my wireless routers, and they will really extend their range. I went back home and tried connecting to my two routers using my laptop with two bricks walls in between 20 meters away from the routers. The built-in WLAN card picked both routers with poor/fair signal. The alfa increased it to good signal with the Aztech pushing slightly more signal. I also tried connecting the high gain antenna to the alfa in this scenario, but nothing changed at all.

It was then time to replace the antennas on my routers with the high gain antennas I got.

Look at the merchant description:

#############################################################
Features and Specificatoin:

Frequency Range: 2.4GHz
Impedance: 50 Ohms
Gain: 13dBi High Gain
VSWR: < 1.8 : 1
Antenna Length: 37.5cm
Extension Cable Length: 3m (approx. 10 Feet)
Base: Magnetic Base

Antenna Connector: RP-SMA
Extension Cable Connector: RP-SMA (Standard SMA Female Connector)

Product Description:

2.4GHz Wireless 13dBi High Gain RP-SMA Female Antenna For WiFi Router



Boost your wireless coverage with this 13dBi Router Antenna. To improve signal strength and signal quality.



Compatibility:

* Compliant with IEEE 802.11b and 802.11g Wireless LANs.
* Operate with AP/Router with RP-SMA Connector

#############################################################

Looks promising, however....

So I connected the antennas to both of my routers expecting to see some increase in signal strength, BUT, there was no increase at ALL. It was exactly the same results with the original antennas that came with the routers!

Maybe it is the walls, and if not for them, the signal would have traveled further? I don't know. Something must be off. The antennas were 25 bucks each. Is this too cheap for an antenna? Looks wise, they look great and were packaged professionally. They don't look like bad cheap quality. So why? Being a WiFi noob, I don't have the guts to fully and accurately analyze the results. So PLEASE gurus, I need your input/comments/feedback. Please don't leave me alone in this.

Question: does more transmit power increase barrier penetration?

In all scenarios, vertical polarity was used just so that you know.


Thanks to all in advanced and feel free to ask questions.
 
Is it like a certain power output is good with some dbi gain antenna and more dbi won't do any good? So, if I have to take advantage of the higher gain antenna, I have to use more power?
 
xSauronx said:
not even a little, thats the best part. 2 watts is nuts and so is the OP.
Click to expand...

Why? What crime have I committed? Is owning this alfa adapter that claims to be 2000 mW illegal ? Then why is it sold everywhere?

http://www.amazon.com/802-11g-Wirele.../dp/B0035H4164

??

Many people are discussing such things:

http://www.wirelessforums.org/network-troubleshooting/alfa-usb-adapter-500mw-anyone-know-39398.html

?

What's up with your people? Why Am I being treated so harshly ? I'm not emitting 2 Watts 2.4 GHz signals, nor I have the capability to. The alfa is essentially a receiver, and I don't even know if it is really 2 watts or whatever.

In these pages, it even says it is compliant with this FCC of yours:

http://ttcshelbyville.wordpress.com/2010/03/23/2000-mw-usb-wireless-2-watts-of-power/

http://fixmonster.com/2000mw-2w-802...wifi-network-adapter-strongest-on-the-market/


So what do you say? I even did a Google search and didn't find anything illegal about it !

Will it be allowed to be sold all over the place if it is not compliant with FCC?

Is this what I should get for trying to learn something more about WiFi? I'm being called nuts and will be reported to some entity I've never heard about before even?. I'm seriously frustrated now. Where are all the helpful people in this great forum?

This thread is very innocent and if you find something wrong with it, enlighten me, don't accuse me.
 
Here's the help. You are allowed to have an Effective isotropically radiated power (EIRP) of up to 4 watts with an omni directional antenna. Above that and you are violating Federal Communications Commission (FCC) law. This limit is to make sure you are not causing interference with other networks.

4 watts is 36 dbm. 2 watts is 33 dbm so the maximum antenna gain you can have is 3 db. The reason they are allowed to sell it is it is up to the user to turn down the power depending on what antenna is being used. You're coupling that with a 14 db antenna, you are over 10 times the legal limit.

More here
http://www.wifihowto.org/?mo=HowTo;Item=9
 
The problem is you are not familiar enough with what you are doing and using 2 watts of power for experimenting is not a good idea.

The alfa unit IS a trasmitter. It has to send signals back to the router and uses 2 watts of power to do it. When it was sold it was supposed to be used only with the antenna it came with. When you change the antenna you broke the rules.

The reason the rules exist is because breaking them doesn't just inconvenience other people it can be harmful to them. When you start sending out 2 watts + at the 2GHZ frequencies you are sending out a signal that can interfere with other devices. Anyone near with something like a pace maker can be affected. Control systems in things like traffic controllers can fail . Not to mention that standing near a 2watt microwave signal is not a good idea. Long term exposure at close range has been shown to damage DNA. While these situations are rare they do exist and is why you are not allowed to use a cell phone in places like hospitals.

If you want to understand more about the signal, use a 500mw setup and do some experimenting. Start reading up on terms like SWR , impedance , and fresnel zones. You might find out why you can hurt reception just by using mismatched antennas, cables, too much power, etc.

If you want distance then check into 900mhz wifi .
 
Ok fair enough. Understood. But, if it this serious, selling out various gains 2.4 GHz antennas should be controlled. Any ignorant body( like me if you will) will just read this nice Ad and buy this nice looking antenna and hook it up to his alfa no problems. What will hold him? Nothing. I'm not a computer illiterate, yet I didn't know hooking up a 13dbi antenna to a famous wireless adapter is really a bad idea!


Regulations aside, why didn't the high gain antennas get more networks?

And yes I want distance. I explained my scenario in the first post. 900 MHz seems unpopular. I want to do it with 2.4 GHz.

Thanks.
 
That might not be the normal gain pattern for an omni-directional antenna. It might be "flatter" than it is "round". Just get a normal card and hook up a directional antenna to it, that's about the best you can do.
 
spidey07 said:
That might not be the normal gain pattern for an omni-directional antenna. It might be "flatter" than it is "round". Just get a normal card and hook up a directional antenna to it, that's about the best you can do.
Click to expand...

Can you please suggest me a good directional antenna I can use with my alfa?


Thanks.
 
>>>>>>>>It might be "flatter" than it is "round"

And I don't really get this. The antenna is round. What's inside is essentially a round metal. So why?

Also, how much power do wireless routers emit? It is less than 500mW, right? So what would be the highest gain good antenna I can use with them?

A 9dbi gain antenna? This is according to the link you provided. And I want good antenna, not a cheap one.

Thanks.
 
i have a crappy horn +14dbi hawking - the biggest junk on the planet and it sure as heck works.


remember omni's fire out AND DOWN like a mushroom. so you need to be at a peak elevation point that is not too high nor too low - relative - to get good results. firing at brick walls isn't doing anything products.

site surveys for long distance wifi include the calculations of the antennas pattern spread (up down left right).

Keep in mind the shielded cabling to the antenna and its quality connector probably have just as much effect as the antenna itself (in the case of hawking - lack of quality).
 
iamgenius said:
Ok fair enough. Understood. But, if it this serious, selling out various gains 2.4 GHz antennas should be controlled. Any ignorant body( like me if you will) will just read this nice Ad and buy this nice looking antenna and hook it up to his alfa no problems. What will hold him? Nothing. I'm not a computer illiterate, yet I didn't know hooking up a 13dbi antenna to a famous wireless adapter is really a bad idea!
Click to expand...

They are controlled, get caught by an fcc field tech and the cost can be from $1k to $250K in fines. Remember ignorance of the law is no excuse. The rules are in the manual you get with the equipment , people just don't read them. The fcc has often driven around areas with reported noise issues to investigate the source.

The second page of my netgear AP manual reads:
This device complies with part 15 of the FCC Rules. Operation is subject to the following two conditions:
&#8226; This device may not cause harmful interference.
&#8226; This device must accept any interference received, including interference that may cause undesired operation

To assure continued compliance, any changes or modifications not expressly approved by the party responsible for compliance could void the user's authority to operate this equipment.

To meet FCC and other national safety guidelines for RF exposure, the antennas for this device must be installed to ensure a minimum separation distance of 20cm (7.9 in.) from persons. Further, the antennas shall not be collocated with other transmitting structures.
Click to expand...



Regulations aside, why didn't the high gain antennas get more networks?

And yes I want distance. I explained my scenario in the first post. 900 MHz seems unpopular. I want to do it with 2.4 GHz.

Thanks.
Click to expand...


It isn't all about antenna gain. You need to read up on impedance and SWR.
If you push a strong signal down a cable and that cable is mismatched for the antenna and transmitter then what happens is like sending water down a pipe with a bunch of bends and holes in the pipe. The water will get to the other end eventually but the flow will not be what it should. The signal enters the cable and as it travels down the cable some of it is reflected back to the antenna where it continues to bounce back and forth along the cable destroying your reception.

A good setup will have the cable and antenna tuned to the transmitter. When tuned the signal will travel down the cable without being bounced back to the source. You need to learn about SWR and how to measure it if you want to start experimenting with antennas.

For distance you want a YAGI antenna. Yagi are designed for sending a signal over a very narrow beam . The downside is that it is so narrow the receiving antenna has to be carefully aligned so they point at each other.

YAGI and Parabolic antenna are not meant to send signal to a laptop. They are used to bring the signal from one place to another over a link. Then once received it is re-broadcast using an omni antenna.

900Mhz is better for distance because the physical length of the wave is longer. Think of the wave as being a length of wire. A 900Mhz wave is about 13 inches long . 2.4Ghz is around 5 inches. There is more to it than that but it should give you the idea. That means any solid object thicker than 5 inches will harm a 2.4Ghz signal. The wave isn't long enough to make it through. The closer you are to the length the more signal you lose until you lose all of it. So 900mhz being 13 inches long can pass through a lot more stuff in between. 5GHz is even worse as it drops to 2.6 inches.
 
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Modelworks said:
They are controlled, get caught by an fcc field tech and the cost can be from $1k to $250K in fines. Remember ignorance of the law is no excuse. The rules are in the manual you get with the equipment , people just don't read them. The fcc has often driven around areas with reported noise issues to investigate the source.

The second page of my netgear AP manual reads:







It isn't all about antenna gain. You need to read up on impedance and SWR.
If you push a strong signal down a cable and that cable is mismatched for the antenna and transmitter then what happens is like sending water down a pipe with a bunch of bends and holes in the pipe. The water will get to the other end eventually but the flow will not be what it should. The signal enters the cable and as it travels down the cable some of it is reflected back to the antenna where it continues to bounce back and forth along the cable destroying your reception.

A good setup will have the cable and antenna tuned to the transmitter. When tuned the signal will travel down the cable without being bounced back to the source. You need to learn about SWR and how to measure it if you want to start experimenting with antennas.

For distance you want a YAGI antenna. Yagi are designed for sending a signal over a very narrow beam . The downside is that it is so narrow the receiving antenna has to be carefully aligned so they point at each other.

YAGI and Parabolic antenna are not meant to send signal to a laptop. They are used to bring the signal from one place to another over a link. Then once received it is re-broadcast using an omni antenna.

900Mhz is better for distance because the physical length of the wave is longer. Think of the wave as being a length of wire. A 900Mhz wave is about 13 inches long . 2.4Ghz is around 5 inches. There is more to it than that but it should give you the idea. That means any solid object thicker than 5 inches will harm a 2.4Ghz signal. The wave isn't long enough to make it through. The closer you are to the length the more signal you lose until you lose all of it. So 900mhz being 13 inches long can pass through a lot more stuff in between. 5GHz is even worse as it drops to 2.6 inches.
Click to expand...

Thanks modelworks, I appreciate all your nice help. The picture is very much clear now.
 
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