Need a little help with antenna selection for a COW

Answered Question
Jan 4th, 2012

Hello fella's...

Ok, so I've gotten myself a little confused here and would like some recommendations.  We are ordering new COWs (Computer On Wheels) for the hospital and they will be using an Intel 6205 Wireless Chip which is a/b/g/n 2x2.  The two new floors these devices will be going on will be our first internal hospital entry into 802.11n which I force the clients to run in the 5ghz range for N.   Previous to this, all of my cows are G clients and use a 2.2dbi rubber duck for 2.4ghz.   I will be using 1142 AP's, if not 3502 and no I have not performed a survey yet as the floor is still in early construction, but equipment is required to be ordered now.  I can tell you that I will be surveying for a voice grade.  I suppose my confusion comes from what is the best antenna (obvious open ended question) for this card, being it has two connectors for the 2x2.  Again, typically I would use a 2.2 dbi rubber duck for either 2 GHz or dual band 2/5 GHz.  Is dual rubber ducks at 6inch spacing (half wavelength met on 2.4 GHz fall back) suffecient or are there other factors involved with the N.

Thanks,

Raun

I have this problem too.
0 votes
Correct Answer by Leo Laohoo about 2 years 3 months ago
BTW, what is the real term for the Rubber Duckie antenna?

I used these term from my experience with UHF/VHF radios.  So "rubber ducks" are the standard omni-directional, articulated (bendable) or not, AIR-AT2422DB/AIR-ANT4941.   I don't know what the old model is called but they're the same.

Rubber duckies are examples like AIR-ANT2422DG.

Rubber ducklings (aka thumb antennas) are AIR-ANT2422SDW.

So the real term of the rubber duckie?  Rubber duckie.

So you think jus two dual band rubber ducks would work for n?

I don't know.  You'll have to tell us what they are because we don't know either.

For dual-band antennas, refer to the last page of the link Antenna Product Portfolio for Cisco Aironet 802.11n Access Points, under the heading Dual-Band Antennas or Table 5.

Correct Answer by Scott Fella about 2 years 3 months ago

Usually they just call then dipole antennas.

Thanks,

Scott Fella

Sent from my iPhone

Correct Answer by George Stefanick about 2 years 3 months ago

Thanks Scott. Sorry, Raun, I interpreted the e-mail as for the access points.

GREAT QUESTION!

Coming from a Helathcare background and having ran into similar issues I can tell you this will be no easy task. We modified Lionville carts because of a similar issue. I also worked for a company that resold Jaco carts and we worked with them on where to mount the antennas. In fact you will see they have their (thumb) antennas on the work top (right corner) or mounted in back of the monitor arm. This was prior to 802.11n and in both cases with went with 1 antenna approach (non diversity).

I have not modified any carts since 802.11n and your question is a great one. Here is whats rambling around in my brain at the moment.

1 - Do the cows really need 802.11n speed. In almost all situations on the healthcare floor the answers is usually no. If this is the case consider turning of 802.11n speeds off on the cows and go with normal protocol. This could mean no diversityingle antenna approach. But what lead would be the single antenna coming out of the card we would have to find that out. If that can even be done with that card ... Never played with it

2 - I am assuming there are 4 antenna leads coming out of the card (2x2) ? Do you know or have a pic of it ? Now Im curious. Without knowing what end connectors we are limited on our antenna options. Ideally, we would want something off the shelf meeting your parttern requirements.

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Average Rating: 5 (3 ratings)
George Stefanick Wed, 01/04/2012 - 10:57

Hey Raun,

The same rules apply for 802.11g as they do 802.11n. Your antennas spacing shold be 4.92 inches apart at its closets point. You can add additional distance with a multipler of 4 between antennas.  The max should be 20 inches (or 4.92x4=19.68 inches).

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

Remember the 2.4 GHz wavelength is the same, just adding a additional stream.

If you are using DUCK antennas, why not just purchase the aps with the integrated antennas?

raun.williams Wed, 01/04/2012 - 11:08

Hey, Thanks for responding George.  These antenna's won't be for the AP, but the client.  The client is basically this:

http://www.metro.com/healthcare/mobile-computing

The hybrid cart pictured on the front page.  Again,  in the past with these carts, depending on what type of PC device or laptop they installed, we'd have the manufacture put a duck on the top shelf next to the monitor.  Of course at that point also the cart was basically a metal box instead of the plastic ones we will be getting.   Instead our new COW's, will be a Wyse Z90 terminal special ordered with the Intel 6205 with antenna cables.  I'm hoping I can use the antenna's that WYSE ships with the devices, but I have yet to get any specs on those and being WYSE does not manufacture their own devices, it's doubtful I will.  Flo would us to use a dual band half moon antenna, in this case two of them for N, but I don't like the pattern so I'd like to stick with an omni-directional.  So that's where the question comes into play with the Intel 6205 card, what's the ideal solution.  Again, my preference is to run in the 5 GHz range and will be surveyed for 802.11a/n with a fall back to G/2.4 and older clients.  You mention the multiple of 4 and 4.92inches at the closest point, this being for 2.4 GHz, how do you handle proper spacing when counting for 2.4 and 5?  Back to the anteanna, recommendations?

Scott Fella Wed, 01/04/2012 - 11:09

George,

I thought he was inquiring about external antennas for the Intel wireless card.

Thanks,

Scott Fella

Sent from my iPhone

Correct Answer
George Stefanick Wed, 01/04/2012 - 11:30

Thanks Scott. Sorry, Raun, I interpreted the e-mail as for the access points.

GREAT QUESTION!

Coming from a Helathcare background and having ran into similar issues I can tell you this will be no easy task. We modified Lionville carts because of a similar issue. I also worked for a company that resold Jaco carts and we worked with them on where to mount the antennas. In fact you will see they have their (thumb) antennas on the work top (right corner) or mounted in back of the monitor arm. This was prior to 802.11n and in both cases with went with 1 antenna approach (non diversity).

I have not modified any carts since 802.11n and your question is a great one. Here is whats rambling around in my brain at the moment.

1 - Do the cows really need 802.11n speed. In almost all situations on the healthcare floor the answers is usually no. If this is the case consider turning of 802.11n speeds off on the cows and go with normal protocol. This could mean no diversityingle antenna approach. But what lead would be the single antenna coming out of the card we would have to find that out. If that can even be done with that card ... Never played with it

2 - I am assuming there are 4 antenna leads coming out of the card (2x2) ? Do you know or have a pic of it ? Now Im curious. Without knowing what end connectors we are limited on our antenna options. Ideally, we would want something off the shelf meeting your parttern requirements.

raun.williams Wed, 01/04/2012 - 11:13

As a side note, the reason I'm not comfortable with the antenna's that WYSE is providing by default is due to the fact this termal is a special order with the Intel card, and quite frankly wyse doesn't seem to know whats going on technically, at least with out talking to the manufacturer.  I'm afraid it's a crap antenna ment for 2.4 only as that's the default card the terminal comes with if I remember correctly.

Scott Fella Wed, 01/04/2012 - 11:19

What type of connectors are on those cards and how many? 2 for each band?

Thanks,

Scott Fella

Sent from my iPhone

raun.williams Wed, 01/04/2012 - 11:51

Gentleman, you are awesome.

The 6205 is a 2x2 with 2 antenna connectors.   They're putting these cards in a lot of baseline business laptops, for example my HP.

http://www.intel.com/content/www/us/en/processors/centrino/centrino-advanced-n-6205-brief.html?wapkw=intel

It's a mpcie card, so it has the little dinky jacks on it, IPX I believe.  In side the wyse terminal these are connected to a cable that goes to RP-SMA, or SMA on the external side of the wyse chassis. To be honest, I don't know how to tell if it's an RP or not.  At any rate, this is where the default antenna's would go.  HOWEVER, as this is still inside the flo cart, and there's not much room for an antenna to stand up, the manufacturer will attach another cable to bring it up to the shelf so an attenna can attach on the outside of the cart.  I'm assuming, we can get them to do an SMA to SMA with out issue. 

To be honest, is there a a reason for N on a cart?  No, not really, other then diversity maybe.  Though on the management side, it's (OMG*@(#&@(* 802.11N IS AMAZING WE HAVE TO HAVE THAT BECAUSE THE NEW HOSPITAL NEXT TO US WILL HAVE IT WHEN THEY OPEN!!!) so there is that aspect too

raun.williams Wed, 01/04/2012 - 13:15

I don't know... I was trying to test this on my laptop, but for whatever reason, doesn't seem to be as easy to do as one would think.. I'm going to say no, if one antenna is removed, then you don't get full mimo bennefits is all, for the moment. heh

raun.williams Thu, 01/05/2012 - 08:19

The best I can tell one is a primary for 2.4 and 5 and the secondary is for extended.  I've emailed Intel support for clarification and specs, but no response so far.

Leo Laohoo Wed, 01/04/2012 - 13:16

Hey Raun,

Before signing the contract for the COWs with blood, can you get a few (three units) for testing?

Sorry, but I don't trust the sales people.  I'd recommend you test a few of these units yourselves.

What antenna ... I'm no big fan of the "thumb" (aka rubber ducklings) or the rubber duckies.  I would, however, recommend the rubber ducks.  The difference?  Rubber ducklings are the "thumb" antennas while the rubber duckies are the mini version of the full size rubber ducks.

Anyway ... Here's another thing:  Does the Wireless NIC card have an antenna socket for each radio?  Or is each antenna socket a two-in-one (802.11a and 802.11b radios)? 

raun.williams Thu, 01/05/2012 - 08:25

No, not really unfortunately.  The WYSE devices were a special order by us, custom built unit.  I had to specify the Intel card instead of a ralink one.  These devices then get direct shipped to our cart manufacture is installs them for us.  They term pc and the cart are two different purchases by us.  Normally we would have an oppurtunity for testing, but right now is a bit of a strange period due to the department being overloaded, EHR go-lives  and construction expansion.

On the radio, see, I'm having a hard time determining that from the card in my laptop.  Simply ripping one antenna out a socket produces inconsistant results for 2.4 and 5 regardless of my position in relation to an ap.  I've emailed Intel Support for details, no reply yet. 

So you think jus two dual band rubber ducks would work for n?

raun.williams Thu, 01/05/2012 - 08:31

BTW, what is the real term for the Rubber Duckie antenna?  I'll be damned if I can find anything on these small versions of the rubber duck.  This is what typically ships with the WYSE terminal by default, but other then that I don't know if they are dual band or anythign about them.  Have been searching high and low to find just a look a like on the internet of these small fries.. any ideas

Correct Answer
Scott Fella Thu, 01/05/2012 - 08:45

Usually they just call then dipole antennas.

Thanks,

Scott Fella

Sent from my iPhone

Correct Answer
Leo Laohoo Thu, 01/05/2012 - 13:28
BTW, what is the real term for the Rubber Duckie antenna?

I used these term from my experience with UHF/VHF radios.  So "rubber ducks" are the standard omni-directional, articulated (bendable) or not, AIR-AT2422DB/AIR-ANT4941.   I don't know what the old model is called but they're the same.

Rubber duckies are examples like AIR-ANT2422DG.

Rubber ducklings (aka thumb antennas) are AIR-ANT2422SDW.

So the real term of the rubber duckie?  Rubber duckie.

So you think jus two dual band rubber ducks would work for n?

I don't know.  You'll have to tell us what they are because we don't know either.

For dual-band antennas, refer to the last page of the link Antenna Product Portfolio for Cisco Aironet 802.11n Access Points, under the heading Dual-Band Antennas or Table 5.

raun.williams Thu, 01/05/2012 - 17:34

I guess I'm under the impression that if you put a dual band antenna on a device, regardless wether it's a 2.4 radio or 5GHz radio, that the antenna would work, as it's well, dual band.  Am I wrong in that assumption leolaohoo?

I have heard back from wyse today with a little information on their provided antenna, but no radiation pattern.  This antenna would be referred to as the 'rubber duckie' style 'dipole'.  I'm not really having much of a choice as it stands now, as I am limited on space(height) to place the antenna and time (chinese new year for manufacturer).  However, one other question. I note that the 1142 and 3502's are horizontally polarized and this omni is vertically polarized.  With my limited understanding of antenna's, that's not a good thing... what is the typical associated 'cost' of a vertical to a horizontal?

  • •1.      Electrical Properties

1.1 Frequency                             2.4GHz ~ 2.5GHz ;4.9GHz~5.825GHz

1.2Impedance……………………50 Nominal

1.3 VSWR …………………………1.92 :1Max.

1.4 Return Loss……………………-10 dB Max.

1.5 Radiation………………………Omni-directional

1.6 Gain(peak)………….………… 2.0dBi@2.4GHz~2.5GHz

2.0dBi@4.9GHz~5.825GHz

1.7 Polarization……………………Linear; Vertical

1.8 Admitted Power………………1W

1.9 Cable……………………………RG-178 Coaxial Cable

1.10 Connector…...…………………SMA Plug Reverse

2. Physical Properties :

2.1 Antenna Body……………. ……TPE

2.2 Antenna Base……………. ……PC

2.3 Antenna Base……………. ……PBT

2.4 Operating Temp. ………………-10 ~ +60

2.5 Storage Temp. …………………-10 ~ +70

2.6 Color …………………………Black

George Stefanick Thu, 01/05/2012 - 19:21

Horizontal vs Vertical. Yes, but in your enviroment not an issue due to the denisty of access points you have.

I would go with the duck, test it call it a day.

Leo Laohoo Thu, 01/05/2012 - 19:32
I guess I'm under the impression that if you put a dual band antenna on a device, regardless wether it's a 2.4 radio or 5GHz radio, that the antenna would work, as it's well, dual band. 

If the radio is a supports dual-antenna then you need the appropriate dual-antenna.  Putting a dual-antenna to a radio that won't support it (or vice versa) renders your radio useless.

This antenna would be referred to as the 'rubber duckie' style 'dipole'.

Rubber duckie is not the same as a dipole (also known as a "disco stick").  A good example of a dipole/disco stick is the AIR-ANT1728 or AIR-ANT2506.  Other than the physical appearance, the difference is the power and the way it's installed.  Disco sticks are commonly mast-mounted or hanging from a roof by itself.

Stephen Rodriguez Thu, 01/05/2012 - 20:01

just to clarify this not the disco stick that Lady Gaga was sing about

Sent from Cisco Technical Support iPhone App

Leo Laohoo Thu, 01/05/2012 - 20:18
just to clarify this not the disco stick that Lady Gaga was sing about

LOL!

Back in the old VHF/UHF years of the 80's, we had terms like super-stick (telecopic antennas) and dipoles.  We didn't know what we called them and disco was the "in" thing.  So we started calling these dipoles "disco sticks". 

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Posted January 4, 2012 at 10:27 AM
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