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New Member

What happens when Ap has two different gain antennas

Hi all..

I have  two question?

In a Warehouse, I have a high density of Access Point 1240, each AP have only the radio  b/g active and each AP has two antennas. One antenna is 2.2 dBi and the other antenna is 5.2 dBi. This affect to the signal, or  throughput?

The Ap is at around 82 feet high, is out of estandar. What happens if I reduce the transmit  power?.Can the wifi client connect to the ap and work fine?

Thanks for your help

Everyone's tags (7)
8 REPLIES
Hall of Fame Super Gold

What happens when Ap has two different gain antennas

One antenna is 2.2 dBi and the other antenna is 5.2 dBi. This affect to the signal, or  throughput?

Depends.  Are the antenas going to the same radio?  Please post the model numbers of both antennas.

The Ap is at around 82 feet high,

That's too high.

What happens if I reduce the transmit  power?.Can the wifi client connect to the ap and work fine?

If it's 82 feet from the ground and you lower the transmission power the clients MAY NOT be able to see the signal so, no, the clients would not be able to connect.

New Member

What happens when Ap has two different gain antennas

Hi Leolaohoo

Are the antenas going to the same radio?  Please post the model numbers of both antennas.

Yes, the antenas going in the same radio of the AP.

The model of anthennas:

AIR-ANT1728

AIR-ANT4941

Best Regards

Hall of Fame Super Silver

Re: What happens when Ap has two different gain antennas

82' is too high! The higher gain antenna you go with, the less it will cover below. You might be better off with a low gain at that height. You can compare the different gain using the elevation chart, but also look at how the built-in ap's toward the bottom of the document performs. You might be better purchasing a few to see which ones work better for you.

http://www.cisco.com/en/US/prod/collateral/wireless/ps7183/ps469/product_data_sheet09186a008008883b.html

Sent from Cisco Technical Support iPad App

-Scott
*** Please rate helpful posts ***
Hall of Fame Super Gold

What happens when Ap has two different gain antennas

The model of anthennas:

AIR-ANT1728

AIR-ANT4941

Good grief!

Who recommended the ANT1728 for 82 feet above the ground?  That's a waste of money!

ANT1728 ain't designed for that purpose.  The signal footprint alone doesn't give you ANY coverage whatsover.

ANT4941???  At 82 feet? 

Can you please draw a vertical diagram of what is between the floor and the WAP?  I mean there's got to be a pretty darn good reason why the WAP is hanging 82 feet up in the air.

The problem is that at 82 feet, the clients down below "maybe" able to hear the wireless signal but unless the clients themselves have a guided antenna pointed towards the WAP, there's no chance the client's wireless signal will be heard by the WAP located in the kingdom of So Far, Far Away.

What happens when Ap has two different gain antennas

If you have two different gain antennas on same radio then:

- closer to the antenna (area the lower gain antenna can cover) things will work fine.

- further from the antenna (location where higher gain antenna can reach and lower gain antenna does not reach) then the performance will be less than the performance when you have two anennas with same 5.2 dBi. The issue will be mainly with traffic sent from the AP to the client.

The reason why is that antenna redunduncy is used to better send/receive and build the original signal if it is corrupted. When the AP sends the far client can receive from one antenna only while when the AP receives from the client both antennas will receive the signal. The difference then is when the client receives the signal from only one antenna where the performance degradatoin is expected.

HTH

Amjad

Rating useful replies is more useful than saying "Thank you"
New Member

What happens when Ap has two different gain antennas

Hi Amjad.

"-further from the antenna (location where higher gain antenna can reach and lower gain antenna does not reach) then the performance will be less than the performance when you have two anennas with same 5.2 dBi. "

So if the performance it will be reduced. The performance it will be better with only one higher gain antenna in the radio the 2.4?

Best Regards

XU

Re: What happens when Ap has two different gain antennas

No.

For closer clients two antennas will always be better.

For farthest clients, the traffic from AP to the client will be almost the same with one higher-gain antenna or two different-gain antennas. While traffic from the Client to the AP is better with two antennas although gain is different on both.

HTH

Amjad

Rating useful replies is more useful than saying "Thank you"
Cisco Employee

What happens when Ap has two different gain antennas

#Two differrent gain or antenna type(with or without RF overlap) works good for one client, when more than one client communicating to different antenna would yield poor performance. see the link below.

#dtpc and datarate would also drastically change based on the client connected antenna that is not discussed in the link.

#With one antenna there won't be diversity and yes there will be a performance hit when compared to having multiple antennas.

#Either use two similar model or one antenna, If you don't have two similar antenna model you can still connect one antenna and on AP's antenna diversity setting you can have either left or rigtht based on the antenna connected to the radio port on AP.

Multipath and Diversity

http://www.cisco.com/en/US/tech/tk722/tk809/technologies_tech_note09186a008019f646.shtml

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