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I support some remote northern canadian sites that use wireless as their only network access. Typically each building has one access point which was placed in the room with the rest of the equipement. Site surveys were not done... In some of the locations signal is very weak. I don't really have the option at this point to run wires and put up another access point but I do have extra access points so I was thinking of adding a repeater in the troubled buildings. Here are some details in terms of the building...Fairly small building, only about 4-5 users at any one time. They have a satellite connection to the internet at 384kbps down and 96kbps up.....I have heard that repeaters will drop the bandwith in half but would it matter in this case?.....

We use Cisco 1240AG access points with the 2.4ghz and 5ghz radios...I was thinking of using the 5ghz radios as the repeater portion but I haven't been able to get them to talk to each other...Can someone outline the role of each radio in this scenerio? or if it would even work...Or any other suggestions you may have for my situation....

thanks.
John..

Have you considered using high gain antennas? Are you trying to cover multiple floors? If not, that is good for using higher gain antennas.

You are correct that repeater mode throughput loss won't be an issue considering your bandwidth needs. Repeater mode is fine, but if higher gain antennas will work, it will be less expensive and more reliable.

If you aren't trying to cover multiple floors at once I'll shoot you some ideas for antenna implementation.

GT

yeah, thats an idea....Its only one floor..We currently use the 2.2dbi dipole antennas...What kind would you recommend?
thanks
john

It all depends on how much gain you need. What signal strength are you currently getting? If you want monster coverage, install a 15dBi antenna. You won't be exceeding FCC maximum power and will add about 12dB of signal to your network. The downside is that an antenna of that gain will be quite a bit larger than dipoles, so physical location of the AP's will make a difference. Do you have room? If so, this is the way to go!

GT

not sure if I need that much gain...Also, the higher the gain the more focused the signal right?..I still need close to 360 degree coverage.....Currently the problem clients are connecting at 1mbps and getting cutting off...I was thinking of something like this

http://www.cisco.com/en/US/docs/wireless/antenna/installation/guide/ant1728.html

All omni-directional antennas will provide 360 degree coverage. The higher gain just reduces the vertical beam width. That's why I asked if it was localized to a single floor.

That antenna you spec'd is only 3dB more gain than you currently have, which isn't much. A dB is a dB, point being if your clients are currently connecting at -80dBm right now, the extra 3dB gain will only bring the clients to -77dBm, which is still sketchy. 15dBi may be an overkill, but 5.2 is too low for what you are trying to do. If you are still localized to a single floor, it won't hurt anything by installing a higher gain antenna.

GT

Here is a link to some RP-TNC antennas that go up to 10 dBi of gain . I have seen some that go up to 12dBi doing a Google search.

http://www.confero24.com//index.php?cName=8dbi-9dbi-10dbi-24-ghz-dipole&osCsid=77648af43f19a784ca50e0a3e4cf6931


Reg

Compughter Escribi?3:

Here is a link to some RP-TNC antennas that go up to 10 dBi of gain . I have seen some that go up to 12dBi doing a Google search.

http://www.confero24.com//index.php?cName=8dbi-9dbi-10dbi-24-ghz-dipole&osCsid=77648af43f19a784ca50e0a3e4cf6931


Reg

Thanks for the link Reg. I like those because they are high gain but still reasonable in size.

John, I would go with the 9dBi. That should give you at least 6dB of gain which should help in your situation.

GT

thanks for the info fellas!...Just a few questions, please excuse the fact I'm a bit of a newbie, I'm just starting to study the wireless stuff seriously...

1. GT- you mentioned that the 5dbi antennas wouldn't make much difference compared to the 2.14dbi. I thought that an increase in 3db effectively doubles your output so wouldn't that make those antennas twice as powerful as the 2.14? I'm sure I'm missing something here...

2. So I don't have to buy Cisco Antennas to go with my aironets? that would make things easier...

thanks!

John,

3dB does double the power, but it takes 6dB to double the range. It is more appropriate to think of it this way:

Let's say your card (in your environment, considering noise) needs to receive -83dBm to achieve 1mbps data rate. You stated that the clients are dropping signal, so that means that your devices are receiving less than -83dBm. (-83dBm is a made up number, but I would bet that I'm close). So, by only adding 3dB's of gain in your antenna, your clients are still on the edge of signal coverage.

Like I said in my previous post, a dB is a dB, meaning that if you only add 3dB to your antenna gain, your clients will only see 3dB improved signal. Of course 3dB is twice the power, but that is the difference between .000000005 mw and .00000001 mw. I do recommend a higher gain antenna than 5dBi.

Yes, you can virtually install any antenna that has the proper connectors (RP-TNC) for your AP. You will save a lot of money by not buying Cisco antennas.

GT