1250 802.11n Brdiging

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Aug 11th, 2008
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I have a project to build a short range link between two buildings about 800-900 meters (half a mile) away from each other using two 1250 in 802.11n mode. the design account for 2 external antennas on each side, 100 ft interconnects & lightning fuses. My question is related to antenna section in 2.4ghz and 5ghz. I believe 2.4ghz is a no brainer with 10 dBi Yagi antenna AIR-ANT2410Y-R, but I have not clue for 5ghz operation, can anyone enlighten me?

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Overall Rating: 2 (2 ratings)
beabrams Tue, 08/12/2008 - 05:50
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are you using the 5.0 to do the bridging? you can only bridge on 1 radio not both at the same time.

LOUIS BOUCHARD Tue, 08/12/2008 - 06:07
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yes, I know i can only bridge 1 radio not both. Can you help with antenna selection in the 5ghz band?

LOUIS BOUCHARD Tue, 08/12/2008 - 07:36
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3 questions and looking for 1 educated guess

q1. can theses two antennas be mass mounted outside?

q2. can I use an adapter to convert from RP-TNC to N to fit more antennas? if so what antenna would you recommend?

q3. is there a maximum gain for antennas on the 1250 radios?

guess: any chances that this setup might work in 5ghz range? or I should stick to 2.4ghz?

CFayNTAdmin83 Thu, 08/14/2008 - 11:09
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A1. Sure, why not? For bridge shots that I setup, most of the time I use a NPRM, or a non-penetrating roof mount. It's pretty much a mast that has supports and allows you to use patio stones or blocks to keep it held down. You could use one of those and then attach a metal rack to the mast horizontally to allow both antennas to mount to the rack. Well, I tend to get a little creative when I set stuff up; there may actually be a kit for dual antennas...

A2. Yes, there sure are. I have some 1310's with the external antenna option going from a N-TYPE cable outside and then converted to RP-TNC inside. I believe I got the required converters from a place called Fab-Corp...

A3. As for the maximum gain, I think that falls into a potential FCC maximum transmit power situation. You may want to watch out for this, but I'd imagine that any standard n-type Antenna ,short of the very high gain ones, would work out fine. Just don't go overkill with it and you shouldn't have any problems. If the run is short then you probably don't need anything over 10Dbi...

A4. I would recommend that you use 5Ghz for the test. It has more open channels. The only potential issue I see with using 802.11N bridging is that if everyone starts putting up N bridges you could potentially get interference from two devices transmitting on the same channel(s). Now, it's probably not likely can you can effectively dominate the radio waves. You may want to get a copy of airmagnet to see what signals in 5Ghz are out there to exclude them from your channel list. Although I haven't dealt with N yet, I'd imagine interference is still interference...

Anyone else play with the 1252 in bridge mode with 802.11N enabled?

jsalb Wed, 09/24/2008 - 00:37
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Which connector on the AP1252AG 5 GHz radio do each of the 2 RP-TNC cables from the ANT5170P-R get connected to? I assume the central connector on the radio module is left unconnected.

And how should the antenna section of the IOS GUI be configured?

dozinov01 Wed, 11/19/2008 - 14:38
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I'm bridging in 802.11N on the 1252's. I'm using 3 Yagi's on each side and not having any interference issues. I'm very happy with this setup.

wesleyterry Wed, 11/19/2008 - 20:10
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2) Isn't it still illegal to use antennas not certified by the manufacturers for their equipment? Isn't this the whole reason why vendors have different connectors types?

I COULD BE WRONG but I still think the FCC certifies devices with the antennas that are allowed to be attached to them. It is illegal to attach any antenna to a wireless device that is not certified by the FCC for that device. Even in the un-licensed spectrums.

So, the idea of hooking a non RP-TNC antenna to a Cisco 1250 could be done, but no professional should ever do it.

Please correct me if I'm wrong.

wesleyterry Wed, 11/19/2008 - 20:25
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I even found a Cisco FCC article ( http://www.cisco.com/en/US/prod/collateral/wireless/ps5679/ps5861/prod_white_paper0900aecd801c4a88_ps469_Products_White_Paper.html ) that states in the Section "Third-Party Antenna Usage" that even though you can use equal or less gain antennas of the same type as any certified antenna with that device, the device still has to have a unique connector.

I'm not sure if this implies that you can modify the connector on the antenna or not. It basically says if it is certified for a patch antenna, then any patch antenna less than the maximum one certified will work. However, I'd still be curious to find hard facts on the changing connectors... It seems like there would be no reason to require unique connectors if it was legal to adapt them independently.

This also means that if the 1250 isn't marketed with Yagi anteannas, that you can't add a yagi to it, even if it says it has the same connector

I'm going to open a new thread on this....

LOUIS BOUCHARD Thu, 11/20/2008 - 05:50
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because I had only 800 meters between my sites. I finally decided to use BridgeWave SLE100. With this setup a I have a full duplex 100mbit/s wireless link. with FTP transfer I get a close to 10 Mbytes/s between two Windows servers


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