Antenna Gurus: What seems to be missing in this picture?
Hello Folks,
Here is the setup:
24 dbi parabolic grid antenna from Sharper Concepts. http://sharperconcepts.zoovy.com/product/YSC-HG2424G
7 dbi omni antenna.
200 mW Senao 2511 CD EXT.
HP Pavillion 8000 series 3.6 GHz 17" WS (Built-in Broadcom a/b/g minicard WLAN adapter)
2003 Server / Knoppix Dual Boot
Netstumbler / Kismet
With built in card, I am able to receive 2 of my friends' signals if I hold my notebook 1 meter out from my window. I can't receive any of them from inside my room.
So I went and purchased 200 mW Senao PCMCIA card and 7 dbi omni and 24 dbi parabolic antennas in order to be able to receive the signal from my room. Unfortunately none of these antennas receive these signals from inside the house even next to the window. The only time they would receive it is when I place the antenna exactly at the same spot where my built-in antenna is catching the signal.
My house is on first floor and there is an adjacent building where my window is facing.
With these higher gain antennas, wouldnt I be able to receive the signal 1 meter inside at least?
I also went to my bf's house to check the setup. He is located at 20th floor. With built-in card, I am able to receive public access points about 10 cms outside his window. But placing both 7 dbi omni and 24 dbi parabolic inside does not do any good and I can't receive the signal there inside the house either. I can only receive the signals when I extend the antennas outside the window (same place as the built-in antenna).
The strange thing is that none of these antennas are picking up more APs than the built-in antenna. Perhaps 1-2 more. His house is on a busy street and there are plenty of APs around.
Third check up from the roof of my building. 5 storeys high. None of these antennas pick up any signals stronger there than the built in antenna and they do not pick up more APs than the built in antenna.
Can someone give me an insight as to what I am doing wrong?
Also, the radiation levels... Just how harmful are these if you stay 1 meter away from them when they are working? Mobile phones disturb me (burning sensation inside my brain) so I dont use them and these antennas seem more powerful (burning sensation right after using them for a minute).
Thanks!
Maria
Here is the setup:
24 dbi parabolic grid antenna from Sharper Concepts. http://sharperconcepts.zoovy.com/product/YSC-HG2424G
7 dbi omni antenna.
200 mW Senao 2511 CD EXT.
HP Pavillion 8000 series 3.6 GHz 17" WS (Built-in Broadcom a/b/g minicard WLAN adapter)
2003 Server / Knoppix Dual Boot
Netstumbler / Kismet
With built in card, I am able to receive 2 of my friends' signals if I hold my notebook 1 meter out from my window. I can't receive any of them from inside my room.
So I went and purchased 200 mW Senao PCMCIA card and 7 dbi omni and 24 dbi parabolic antennas in order to be able to receive the signal from my room. Unfortunately none of these antennas receive these signals from inside the house even next to the window. The only time they would receive it is when I place the antenna exactly at the same spot where my built-in antenna is catching the signal.
My house is on first floor and there is an adjacent building where my window is facing.
With these higher gain antennas, wouldnt I be able to receive the signal 1 meter inside at least?
I also went to my bf's house to check the setup. He is located at 20th floor. With built-in card, I am able to receive public access points about 10 cms outside his window. But placing both 7 dbi omni and 24 dbi parabolic inside does not do any good and I can't receive the signal there inside the house either. I can only receive the signals when I extend the antennas outside the window (same place as the built-in antenna).
The strange thing is that none of these antennas are picking up more APs than the built-in antenna. Perhaps 1-2 more. His house is on a busy street and there are plenty of APs around.
Third check up from the roof of my building. 5 storeys high. None of these antennas pick up any signals stronger there than the built in antenna and they do not pick up more APs than the built in antenna.
Can someone give me an insight as to what I am doing wrong?
Also, the radiation levels... Just how harmful are these if you stay 1 meter away from them when they are working? Mobile phones disturb me (burning sensation inside my brain) so I dont use them and these antennas seem more powerful (burning sensation right after using them for a minute).
Thanks!
Maria
That royally sucks! I really couldn't tell you whats going on. Did you plug the antennas in?
Hello CountX,That royally sucks! I really couldn't tell you whats going on. Did you plug the antennas in?
Senao card does not have built in antenna. So it does not receive anything at all without having any external antenna connected.
This issue is really pissing me off. Aren't these high-gain antennas supposed to offer better range?
There has gotta be something set up wrong, with that card and those antennas you should be seeing lots of networks. You aren't living in a building covered in copper wire mesh, are you? What are the pigtail and cable specs?
I get 18 networks with my senao 2511 and 8dBi omni in my apartment.
I get 18 networks with my senao 2511 and 8dBi omni in my apartment.
That would be my first question... what type of antenna cable and connectors are you using and how long is the cable? With most cable that can be carried around with a laptop, more than a few feet of it will cut the signal to the card greatly.
Apollyon
Apollyon
as everyone else has said, either external antenna should get *many* more AP's than the builtin. you may possibly not be configuring your apps to use the Senao card correctly? i have never used Netstumbler, but the kismet.conf file specifies which device and it's chipset that Kismet will use. Kismet works very well (and has signal strength indicators), but it rarely will work by just plugging in the card without editing the kismet.conf file. the kismet.conf file is very well documented, the base docs are here.
Seattle Wireless has a good page on this card and it's variants. apparently some Senao 2511's are Prism 2.5 chipset (good) and some are Prism3 chipset (less good).
as far as safety, I read in the 'Great Somewhere' that is the internet, that you should stay five feet behind a 19 DB grid while it is transmitting. this is assuming freespace, if the antenna is on the roof of a car and you are inside, i would say that is very safe. the Senao cards can transmit at 200mw, which is quite high compared to an old Lucent/Orinoco's 30mw. remember that kismet is completely passive and does not transmit at all. Netstumbler transmits constantly. Kismet is completely safe as far as radiation goes.
Seattle Wireless has a good page on this card and it's variants. apparently some Senao 2511's are Prism 2.5 chipset (good) and some are Prism3 chipset (less good).
as far as safety, I read in the 'Great Somewhere' that is the internet, that you should stay five feet behind a 19 DB grid while it is transmitting. this is assuming freespace, if the antenna is on the roof of a car and you are inside, i would say that is very safe. the Senao cards can transmit at 200mw, which is quite high compared to an old Lucent/Orinoco's 30mw. remember that kismet is completely passive and does not transmit at all. Netstumbler transmits constantly. Kismet is completely safe as far as radiation goes.
Ring out the cable with a ohm meter=0 or so=good,I had one look good but the center conductor failed at the N-Connector,good luck and stay on the path of connection fromthe Radio to the Ant.
You can have to much power. If you are to hot you can overpower the ap.
What to do
1st make sure YOUR ap is working
2nd take laptop, antenna and go for a walk away from your ap and see what happens.
3rd If this doesn't fix check you cables,It doesn't take much to break them
What to do
1st make sure YOUR ap is working
2nd take laptop, antenna and go for a walk away from your ap and see what happens.
3rd If this doesn't fix check you cables,It doesn't take much to break them
Maria,
You may have heard the saying "there's no such thing as a free lunch." In the case of antennae, there's no such thing as free gain. The YSC-HG2424G antenna that you purchased has a very high gain in one direction. That gain comes at the cost of sensitivity at all other directions. In short, your antenna is only useful when aimed precisely at your target.
To properly aim this antenna, you will need a rifle scope or something similar to obtain ballpark elevation and azimuth settings for the antenna mount. This mount should be firmly attached to your roof or chimney so it moves as little as possible. Once the antenna is mounted, you'll have to make small adjustments to get the best signal strength.
BTW, this is a line-of-sight deal. If you can't see the other antenna, all the gain in the world isn't going to help you. Also, unless your friends all live within the 8° beamwidth of this antenna, it's strictly point-to-point. However because the reflector isn't symmetrical, that 8° figure is along only one plane. With the reflector mounted as the picture shows, the beam will be narrower vertically than horizontally. IME the specs are all "best case" numbers, so you should have a few more degrees of panorama.
All of this means nothing if you don't get the polarization right. Notice that the cross-polarization rejection figure is greater than the antenna's overall gain. This means that if you have the feed horn mounted for horizontal polarization, and all of your friends are using the usual omnidirectional antennae, you might as well connect that expensive Senao card to a brick.
Bottom line--the giant antenna probably doesn't suit your needs. For it to be of any use, it must be professionally installed, and the radio must be up at the antenna, not plugged into your laptop.
I don't know if your 7dBi omni is suitable for outdoor use, but the simplest solution is to mount it where it gets the best signal, and keep the wiring as short as possible. If you own the building, or if your landlord approves, you can use a mounting kit that places the antenna a meter or so away from the side of your building. The antenna should have an "N" connector on it. Using N connectors and the right coax for 2.4GHz will keep signal loss to a minimum. Because the right coax is roughly 2cm in diameter, you will need to drill a hole in your wall to feed it through. Unless you or someone you know has the tools and skills to attach N plugs to the cable, it's better to buy a pre-made length of the low-loss cable and make sure that the hole is large enough to fit the connector as well. Then you use a short (< .5M) pigtail to provide a more flexible connection to your computer.
As for RF radiation, don't worry. The only burning sensation that you're likely to get from handheld mobile phones is the heat from the electronics. At such high frequencies, RF energy can't even penetrate your skin, and the power levels are almost nil. The "flip phone" style is best because it places the antenna away from your head whle in use. That puts most of the RF energy where you want it, and is an extra precaution against any RF-induced effects.
At 2.4 GHz you do want to avoid standing right in front of a high energy beam path. Microwave ovens use this same frequency to excite water molecules, which makes heat and in turn cooks your food. Since people are mostly water, the RF energy from a Wi-Fi card could theoretically warm them up a tiny bit. However the difference between the brief 0.2 W pulses from your Senao card and a continuous 700 W (typical of a microwave oven) is huge, so there's no chance of being cooked.
Neither cellphones nor Wi-Fi radios emit ionizing radiation, the kind that causes harm. So if the radiation from a 60 W lamp doesn't bother you, the milliwatt radiation from consumer radio devices will certainly not either.
You may have heard the saying "there's no such thing as a free lunch." In the case of antennae, there's no such thing as free gain. The YSC-HG2424G antenna that you purchased has a very high gain in one direction. That gain comes at the cost of sensitivity at all other directions. In short, your antenna is only useful when aimed precisely at your target.
To properly aim this antenna, you will need a rifle scope or something similar to obtain ballpark elevation and azimuth settings for the antenna mount. This mount should be firmly attached to your roof or chimney so it moves as little as possible. Once the antenna is mounted, you'll have to make small adjustments to get the best signal strength.
BTW, this is a line-of-sight deal. If you can't see the other antenna, all the gain in the world isn't going to help you. Also, unless your friends all live within the 8° beamwidth of this antenna, it's strictly point-to-point. However because the reflector isn't symmetrical, that 8° figure is along only one plane. With the reflector mounted as the picture shows, the beam will be narrower vertically than horizontally. IME the specs are all "best case" numbers, so you should have a few more degrees of panorama.
All of this means nothing if you don't get the polarization right. Notice that the cross-polarization rejection figure is greater than the antenna's overall gain. This means that if you have the feed horn mounted for horizontal polarization, and all of your friends are using the usual omnidirectional antennae, you might as well connect that expensive Senao card to a brick.
Bottom line--the giant antenna probably doesn't suit your needs. For it to be of any use, it must be professionally installed, and the radio must be up at the antenna, not plugged into your laptop.
I don't know if your 7dBi omni is suitable for outdoor use, but the simplest solution is to mount it where it gets the best signal, and keep the wiring as short as possible. If you own the building, or if your landlord approves, you can use a mounting kit that places the antenna a meter or so away from the side of your building. The antenna should have an "N" connector on it. Using N connectors and the right coax for 2.4GHz will keep signal loss to a minimum. Because the right coax is roughly 2cm in diameter, you will need to drill a hole in your wall to feed it through. Unless you or someone you know has the tools and skills to attach N plugs to the cable, it's better to buy a pre-made length of the low-loss cable and make sure that the hole is large enough to fit the connector as well. Then you use a short (< .5M) pigtail to provide a more flexible connection to your computer.
As for RF radiation, don't worry. The only burning sensation that you're likely to get from handheld mobile phones is the heat from the electronics. At such high frequencies, RF energy can't even penetrate your skin, and the power levels are almost nil. The "flip phone" style is best because it places the antenna away from your head whle in use. That puts most of the RF energy where you want it, and is an extra precaution against any RF-induced effects.
At 2.4 GHz you do want to avoid standing right in front of a high energy beam path. Microwave ovens use this same frequency to excite water molecules, which makes heat and in turn cooks your food. Since people are mostly water, the RF energy from a Wi-Fi card could theoretically warm them up a tiny bit. However the difference between the brief 0.2 W pulses from your Senao card and a continuous 700 W (typical of a microwave oven) is huge, so there's no chance of being cooked.
Neither cellphones nor Wi-Fi radios emit ionizing radiation, the kind that causes harm. So if the radiation from a 60 W lamp doesn't bother you, the milliwatt radiation from consumer radio devices will certainly not either.
RF-LOS not visual LOS. While you may be able to cheat physics in a very short link you will not in a long link. It's best to attempt to meet the required freznel zone clearance....
BTW, this is a line-of-sight deal. If you can't see the other antenna, all the gain in the world isn't going to help you. Also, unless your friends all live within the 8° beamwidth of this antenna, it's strictly point-to-point. However because the reflector isn't symmetrical, that 8° figure is along only one plane. With the reflector mounted as the picture shows, the beam will be narrower vertically than horizontally. IME the specs are all "best case" numbers, so you should have a few more degrees of panorama.
...
Would it be more advantages to use a flat panel in this situation,nice lobe pattern,just enough to cut down back noise and still enough gain to reach the target radio, 
.
.At 2.4 GHz yes, they are the same.RF-LOS not visual LOS.
Of course electromagnetic radiation can penetrate some things that stop photons cold. This is an attenuation issue, not a line-of-sight issue. Sure, you can use an AP in another room where you can't see it. But being able to get a Wi-Fi signal from a few meters away through an inch of sheetrock is on a whole different scale than trying to do the same through hundreds of meters of steel, concrete, wood etc.
You can cheat in physics class, but "cheating physics" is a non sequitur. Physics, like other scientific disciplines, is the study of nature. And as the saying goes, "you can't fool Mother Nature."While you may be able to cheat physics in a very short link you will not in a long link.
The effect that you refer to is named for Augustin Jean Fresnel. I'm guessing that you misspelled his name because you have also learned to mispronounce the name FREZ-nell, with a "Z" sound. The proper pronunciation is fre-NELL; the S is silent.It's best to attempt to meet the required freznel zone clearance.
Unfortunately your attempt to impress has backfired in a most ironic way. You see, Fresnel lived until 1827. A whole century would pass after his death before man would be able to master radio frequencies high enough to test his theory on them. In other words, Fresnel's work relied completely on the study of visible light!
Needless to say, obstructions (such as the neighboring building that was mentioned) that lie smack dab in the middle of the line of sight don't need anything as esoteric as the Fresnel Effect to explain...
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