Repeater with 2 Antennas ? One for Receiving One for Transmitting

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Thunder

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Wannabe Geek
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#24569 28-Jul-2008 06:12

Hi Guys,

I assume the setup which I am trying to accomplish here is a bit different as I wasn't able to google for any significaint information about how to achieve that.

Basically, I want to be able to RECIEVE a signal using an Directional OUTDOOR antenna and then using an Omni directional INDOOR antenna I want to transmit this signal into my house so I can have access to the network inside my house.

I thought about connecting the OUTDOOR antenna into a universal repeater, but the problem is that the repeater only has ONE Antenna (even the ones who have 2 antennas actually have just one radio inside so they are useless). And I will will connect the repeater to the Outdoor directional antenna it would only be able to catch the signal fine, but it won't be able to re-transmit the signal into my apartment because the Outdoor directional antenna is no good for that.

Any easy and smart ways around it? Can someone suggest a detailed setup for that?

Thanks
Thunder

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#151950 28-Jul-2008 07:24

You are better off with two radios, and use two freuquencies, repeaters half throughput, and as you have found only have one antenna assy. Two radios, one as uplink with directional antenna and one as AP for your home and put them on two different channels (at least 6 ch appart) is a better option. Some seperation may also be needed.

Cyril

Thunder

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Wannabe Geek
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#151962 28-Jul-2008 08:32

thanks for the info. so i need one repeater/ap that is connected to the outdoor antenna and then another one that is connected to the indoor antenna. i will use different channels for communication to avoid interference, but how do i exactly connect between the two repeaters/aps ? via CAT5 cable? or other way ? Is there any kind of other special configuration ? as i am not wifi savvy.

cyril7

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#151969 28-Jul-2008 08:48

You dont need a repeater, just a AP that can run in client mode to act as the uplink, and another as the AP for the house. You link the two with cat5, physical seperation is ideal, Typically the uplink would be sited outside to allow the antenna cable to be as short as possible.

Maybe you could describe the gear you currently,have, what are you uplinking from and the physical layout etc.

Cyril

iainw

75 posts

Master Geek

#151973 28-Jul-2008 08:58

Do you have any control over the frequency of the outdoor signal you are trying to connect to? Typically you would use 802.11a (5GHz) for your backhaul (outdoor connection), and 802.11b/g 2.4GHz for the client coverage (indoors) - in which case you can use a dual radio access point to achieve what you want.

Generally speaking, it is a really bad idea to use diversity antennas to increase your coverage footprint - ie have the antennas facing in different directions. Diversity in an 802.11 access point, essentially selects the strongest of the two signals for recieving, and then ALWAYS transmits on the antenna it last recieved on. If the antennas are covering the same area, this works perfectly to mitigate multipath interference. If you point them in different directions, all sorts of wierd things start happening. In your case, the signal would be recieved from outside, then retransmitted outside if using a repeater.

It will also give you hidden node problems if you have several clients connecting. When a client decides to transmit, it indicates in its data packet how long it needs to use the airwaves. This is then repeated by the access point's acknowledgement frame. If the data is recieved on antenna A, and the acknowledgement is transmitted on antenna A, a laptop sitting in antenna B's coverage, thinks the air is clear, and will transmit right over the top, increasing interference, packet loss, and generall buggering up the performance of your network.

Thunder

8 posts

Wannabe Geek
Inactive user

#152241 28-Jul-2008 23:11

cyril7: You dont need a repeater, just a AP that can run in client mode to act as the uplink, and another as the AP for the house. You link the two with cat5, physical seperation is ideal, Typically the uplink would be sited outside to allow the antenna cable to be as short as possible.

Maybe you could describe the gear you currently,have, what are you uplinking from and the physical layout etc.

Cyril

Thanks for info. What I actually have is just a :

* Flat panel antenna (Used as the outdoor antenna)
* Luxul 1 watt indoor amplifier (which i though to connect to the outdoor antenna using the 3 meters cable as i have a small chamber on the roof which I can place the amplifier and the ap in, I hope 3 meters cable from antenna to amp won't degrade much)
* 3 meters LMR400 cable
* 5 meters LMR400 cable
* U.S.Robotics router 9113

I would purchase what ever is necessary, which as I understand is simply 2 APs (I assume any model is ok, though not sure). And a cat5 cable running through them (that would be quite a long cable to run from the roof to my apartment). I am not trying to be cheapie here, I would purchase whatever more is necessary, as I am after a good and not too difficult setup.

Thanks

cyril7

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#152286 29-Jul-2008 08:39

Hi, I dont know where you are I presume the States, forget the amp and antenna, more effective options are proper outdoor APs, such as this use it in Client Bridge to your remote host. I have used the Ext verions as APs backhauled off Motorola Canopy systems they are good performers for the money. If you are in NZ then GoWiFi also has them. Use your 9113 as you inhouse AP.

my 2c

Cyril

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Thunder

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Wannabe Geek
Inactive user

#152877 31-Jul-2008 08:01

Hi Cyril,

Thanks for the info.
I checked the ENGENIUS solution. It seems like a good hassle free solution. I liked not having to deal with multiple items and connections. It's nice to have the Accesspoint brdige, the Antenna, the Amp, Surge protector and POE everything in one what seems to be an easy to setup solution that I need more is just to connect with cat5 to my indoor AP and I'm pretty much done with it.

But the best model of the Engenius that I could find was one with 400mW amplifier and 16dBi patch antenna. And that seems to be a bit weak for my purposes cause the signal I need to catch in a bit far. It seems to me that the Luxul 1 Watt amplifier I already have along with my 19 flat panel antenna could give better results in terms of distance, since it's 1watt and 19dbi antenna vs. the Engenius 400mw and 16dBi antenna. So I am not sure now which way to go :( Also I think there is some kind of advantage (not sure how much advantageous that would be though) that the Engenius integrated solution seems to be free of cable loss, since ther are no cables running from the amp to the antenna the antenna to AP since it's all in the same box.

What do you think ?

Thanks
Thunder

cyril7

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#152893 31-Jul-2008 09:27

Hi, exactly how far are you from your host AP, and is it clear line of sight. Do you know from the AP what kind of signal strength you are getting from your current setup. The all inone enclosed Engenius is much tider and a good product. You could also concider the EXT version that has no builtin antenna but in the same weather proof box that mounts on the pole directly behind your antenna, you can then get away with a 150-300mm cable, 3m of LMR400 has roughly 0.8dB of loss. this solution would still be 4dB down on performance compared to your current Luxul solution, but without knowing what link budget you have cannot comment futher.

Other than that just a stay with what you have and get a cheap AP that runs in client/bridge like the TP-Link to drive your amp to the remote host.

Cyril

Thunder

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Wannabe Geek
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#153172 1-Aug-2008 03:22

Hi, thanks again for the response. I will update you soon on my decision about the right gear.

iainw

75 posts

Master Geek

#153203 1-Aug-2008 08:54

I hate to throw a potential spanner in the works... but even ignoring the transmit power of the radio, if you use a 1W amp with a 19dBi antenna, you are already at 49dBi - which illegal in most countries for a Point to Multipoint connection.....

Depending on your modulation rate, your best case legal maximum in NZ is 36dBm assuming you are using 2.4GHz, or 4W EIRP (Equivalent Isotropic Radiated Power - the ammount of energy coming out the tip of the antenna).

cyril7

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#153206 1-Aug-2008 08:58

Ian, I must admit I was wondering the same, hence why I asked where he lived.

Cyril

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iainw

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Master Geek

#153209 1-Aug-2008 09:10

On the other hand - given that he is planning to blast that much energy through - maybe its a good idea not to tell anyone where he lives ;-) As long as it isn't next to me, I don't mind too much.

I'm also wondering where he would conceivably need that much power... even assuming the remote AP has a perfectly isotropic antenna, you could still connect up to 15km with a 100mW radio...

Thunder

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Wannabe Geek
Inactive user

#153443 1-Aug-2008 21:21

To all the worried people.
I live in Kazakhstan.
It is perfectly legal to have that kind of equipment down here. As long as you are not broadcasting pirated Radio or interfering air port communications (these are the only 2 restrictions they have down here), theoratically you can also put a 25w amp if you want (though i can't think a use for that) and if you are that rich to obtain one. There is nothing in the rules to forbid that. It's not a much developed country so I think they didn't think of that yet. Besides last time when I tried to use my 19dbi flat panel antenna with 100mw I couldn't even catch a free hotspot that was 400 meters away cause there was no line of sight as there was a building in the middle. So not sure how you said a 100mw can get a 15km away signal that uses a normal antenna.

Thanks
Thunder

iainw

75 posts

Master Geek

#153450 1-Aug-2008 21:44

O to live in Kazakhstan.

15km assumes a clear RF line of site. The other thing to bear in mind is that RF line of site requires much more clearance than visual line of site. Using radio waves, depending on the length of the bridge link, you can require several metres of clearance below the direct line, otherwise it is not clear line of site.

If there is a building between you and the hotspot, you can almost forget about getting that signal...

Things that affect an RF signal strength in order during transmission
- radio output power
- any cable losses
- any amp gains
- transmititng antenna gain
- Free space path loss
- any interference/impedence
- recieving antenna gain
- recieving cable losses
- recieving amp

When recieving, your amp is only effective, after the signal reaches your antenna. If there is a big fat building in the way, chances are there is no signal left for you to amplify. In which case it doesnt matter what antenna or amp you have.

For the sort of link you are trying to create, I would google the following terms, and THEN plan your link
FSPL (Free space path loss)
Polarisation
Freznel Zone

Any chance of providing the GPS co-ordinates of the two end points? I can tell you exactly what you are dealing with if you have this...

Thunder

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Wannabe Geek
Inactive user

#153475 1-Aug-2008 23:14

Thanks for all the great info. I knew it would be difficult to get a signal when a big building is standing in between, but I was quite sure that a powerfl 19dbi antenna along with 1watt amp would more than likely do the job. I guess I underestimated these building in between. Unfotunately, I don't have GPS coordinates, I threw away my old pocket pc with GPS cause it was so damn slow. Anyway I will do some testings soon and see how it goes. I assume to have probs on the way so will keep an update here.

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