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Community Member

5GHz Antennas on 2.4GHz radio?

Hi,

This might be kind of a stupid question, but I can't find anything about this on the internet.

It is as following:

We ordered 2 Cisco AIR-LAP1242AG-E-K9 Wireless Access Points with 4 AIR-ANT5135D-R antennas.

We accidentally ordered the 5GHz antennas instead of the 2.4GHz antennas.

Would it be possible to use the 5GHz antennas as 2.4GHz antennas?

If so, are there any down sides to it?

Thanks in advance!

Jeffrey Schotte

Everyone's tags (5)
1 ACCEPTED SOLUTION

Accepted Solutions
Community Member

5GHz Antennas on 2.4GHz radio?

This is more of a Physics question.

You can try using 5GHz antenna on a 2.4GHz radio, however, the SWR must be very high and not much RF will be radiated from the antenna.  Most RF energy stays in the transmission line as a standing wave and consumed by finals of the radio as heat.  That means, the reachable range is significantly shorter and the RF final may be fried due to high SWR.  Some high end radios have SWR detecting circuit and take appropriate action to protect the RF finals, but I am not sure those APs have such feature.

Why don't you use just 5GHz radio and leave the 2.4GHz radio turned off?  5GHz spectrum is so much cleaner and easier to deal with.  You can keep everything in 5GHz unless your CIO has an iPhone and is very demanding.

15 REPLIES

5GHz Antennas on 2.4GHz radio?

You can use the antennas but they won't give you efficient coverage.
The antenna pattern is designed based on the frequency and since the frequency is different the antennas that were designed to work with 5 GHz won't efficiently work with 2.4 GHz radio.

For more info about antenna patterns you can read this:  http://www.cisco.com/en/US/prod/collateral/wireless/ps7183/ps469/prod_white_paper0900aecd806a1a3e.html

HTH

Amjad

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

Re: 5GHz Antennas on 2.4GHz radio?

Thanks for your response!

I'll definitely read the document you linked to.

Hall of Fame Super Blue

Re: 5GHz Antennas on 2.4GHz radio?

No you can't.

If you stick the 5Ghz antenna into the 2.4Ghz radio, nothing will happen. Your signal will be bad and you might run the risk of permanently damaging the radio after a prolong use.

Sent from Cisco Technical Support iPad App

Community Member

Re: 5GHz Antennas on 2.4GHz radio?

Well, I just found out that there are more sites where a similar setup has been deployed. They are working and there are no complaints from the users about a bad signal or something like that.

Maybe it's not performing optimal, but I can live with that.

You said the 2.4GHz radio could be damaged from using a 5GHz antenna. Can you explain how that can be? I can imagine it might not be good for the antenna, but how does that damage the radio? Please explain.

Cisco Employee

5GHz Antennas on 2.4GHz radio?

it is possible to fit 2.4ghz antenna on 5ghz radio port and vice versa, if they use similar connectors on any AP. But it is not a best practice also you could end up violating fcc since you do not know what's the total power emitted by the antenna when using high gain antennas. What you're trying to do is not Cisco supported.

Hall of Fame Super Silver

Re: 5GHz Antennas on 2.4GHz radio?

Leo is suggesting in long term it might. You should not use a 2.4 antenna on a 5ghz radio as the antenna is made for the 2.4ghz only. Go buy a dual mode antenna then, this way it's built for either radio band. There are more post saying you shouldn't, than post saying that it works. You can go try it and see for yourself how well it works, but if your trying to do this in an enterprise, you are going to be in for a surprise. Home setup, sure.... You just need to be close to the AP.

Sent from Cisco Technical Support iPhone App

-Scott
*** Please rate helpful posts ***
Community Member

5GHz Antennas on 2.4GHz radio?

It's the other way around.. I have a 5GHz antenna, and I want to use it on a 2.4GHz radio..

Hall of Fame Super Silver

Re: 5GHz Antennas on 2.4GHz radio?

It doesn't matter what antenna or radio, if it's not made for the frequency, it's not guaranteed to work. You just need to try and do some testing and form the results you can determine if it works for you or not. I believe all of us here would not do it.

Sent from Cisco Technical Support iPhone App

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

Re: 5GHz Antennas on 2.4GHz radio?

Honestly now, Saravanan, Scott and Amjad!

WTF have you guys been doing????

Another "3" for valid explanations and/or recommendations that would warrant a "5" (or more).

Gee whiz guys.  Y'all need to work your "delivery".  LOL!

Cisco Employee

5GHz Antennas on 2.4GHz radio?

Hi Leo

Not sure the discussion originator sees it, i value your ans +10 for you.

Thanks

Van

Community Member

Re: 5GHz Antennas on 2.4GHz radio?

The 3 is for basically just using "it wasn't made for it" as the main argument for not doing it. I was looking for a more scientific argumentation as to why it wouldn't be a good thing to do. What exactly would be the down sides and why. They're being helpful, but not very, that's what the 3 is for.. And that I value their effort is the reason I even give them a "helpful".
I did not get the arguments I needed to convince my colleague to not send the equipment to the location it was going and wait for the new antennas to arrive.

Anyway I do value your efforts. Thank you guys for helping.

Hall of Fame Super Blue

Re: 5GHz Antennas on 2.4GHz radio?

It's the other way around.. I have a 5GHz antenna, and I want to use it on a 2.4GHz radio..

None of us wireless implementors, in our right-state-of-mind, are willing to support and/or recommend sticking a 5 Ghz antenna into a 2.4 Ghz radio.

Amjad, George, Stephen and Surendra, you want to add something to this debate?

The main issue is this:  Presume you DO happen to just "do-it" and somewhere down the road people start complaining about the signal quality, NO ONE will blame you.  Instead they'll blame the manufacturer for "supporting" this kinda setup.  (And don't forget that in the long term, you run the risk of severely damaging the 2.4 Ghz radio.)

Put your excess 5.0 Ghz antenna up for sale, say, in e-bay.  You minimize your loses.

Community Member

5GHz Antennas on 2.4GHz radio?

This is more of a Physics question.

You can try using 5GHz antenna on a 2.4GHz radio, however, the SWR must be very high and not much RF will be radiated from the antenna.  Most RF energy stays in the transmission line as a standing wave and consumed by finals of the radio as heat.  That means, the reachable range is significantly shorter and the RF final may be fried due to high SWR.  Some high end radios have SWR detecting circuit and take appropriate action to protect the RF finals, but I am not sure those APs have such feature.

Why don't you use just 5GHz radio and leave the 2.4GHz radio turned off?  5GHz spectrum is so much cleaner and easier to deal with.  You can keep everything in 5GHz unless your CIO has an iPhone and is very demanding.

Hall of Fame Super Blue

5GHz Antennas on 2.4GHz radio?

This is more of a Physics question.

I'm a Physics (class) drop-out.

Highest achievement:  F-

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