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I've been drafted into wireless setup issues by my company as I was the networking guy. Having never touched wireless before. A sub-contractor's setup was being questioned across multiple sites. So I've spent the last few months deep in study and I have now changed the setup of alot of autonomous AP.

All the AP have been set to use diversity, whether they had 2 antenna or not. (99.9% are single antenna)

On questioning this 3rd party about the reasons for setting up all AP on diversity for the 1y and 2y antenna connectors. I was told this was to allow the engineer to fit the antenna to either point.

Does that sound correct?

My thoughts were that this was causing the AP to do work determining which antenna to use that wasnt needed. Plus if they cant fit a cable to a connector labelled primary, 10cm to the side of the 2y connector. ...........?

So I have changed this particular setting across them all. With all the other tweaks I have made on the AP as I learn. I am told that there as been a improvement, the wireless devices are pretty fussy and are now spending less time transmitting their data.

So each AP has two antenna connectors, but only one of them has an RF cable with antenna connected? If I read that right, that is a big red flag. A no no for sure.

Diversity MUST use two antennas to operate. The rules for diversity: Each antenna connector must use the same antennas and they both must cover the exact same area.

Is your deployment indoors? If so, diversity is highly recommended as it helps the AP deal with multipath issues.

Not sure if I'm answering your questions. Let us know if we can help further.

GT

Thanks GTHIll.

Ye, you've answered my question with the big red flag. Just as I thought. I think they probably heard 'diversity is great' but never actually learned anything about it.

Its nearly all outdoors.

Oh, the one AP that had 2 antenna. One dipole antenna inside a building and a semi-directional antenna outside pointing into a yard. This would have been a second Question but you have answered this to.

Thanks again, I thought I was going mad.
:)

Thanks for this one guys.

It never amazes me to open up some device that uses a PCMCIA or CF card internally that comes with diversity, made by Motorola perhaps, and then having the company integrating it into their product not use it.

I think you should always give your devices the best chance possible.  How can removing diversity do that?

I doubt that diversity is going to cut down your battery life much - anyone?

Yes, I would imagine that diversity operation would have minimal effect on battery life. Usually there will be some sort of fast acting switch with associated control logic. Older radio systems used to use PIN diodes in the switching matrix.

One of the biggest consumption "gobblers" is the transmitter when it ramps up at the beginning of operation or after coming out of power-save [ sleep mode ].

Dave

I know at least some Cisco AP's that have diversity, have the ability in their GUI interface to disable one or the other antenna.

I actually use that on the AP used with our environmental chambers. The AP sits about 2 feet away from the chambers side instrumentation port, and I run in a cable connected to a bulkhead connector if I need to test inside the chamber.

You might think a big metal chamber would be sealed up real well against RF - NOT. Even with extra shielding in place it was like a sieve. I guess that makes sense as they say unless it can hold water it' going to leak RF too.

Years ago, some manufacturers actually put two "antennas" on their AP's. I had to open one up one time to replace a ROM chip. As has been mentioned previously, there was no cable connection from the second antenna.

But what was an eye-opener was that when I pulled off the second "antenna", it was just a piece of plastic with no metal in it at all !!

I pulled out the manual and found that there wasn't a peep about diversity. They just wanted to give the impression !!

Truth in advertising..........

Dave

Geez Dave thats shocking wanna name and shame!!!!

I was working overseas and it came from a country I won't mention, as there are some readers from there. I've opened up "new servers" bought from the same place [ "because we have decided it will save us money" ] and found old re-conditioned hard drives inside. Power supplies inside that were supposed to be brand new, and you could see where replacement zener diodes and filtering capacitors had been placed. Satellite communications antennas have to be built to precise specifications. The larger the antenna, the more precise they have to be. A huge project. "We're buying them from X". "Don't recommend it. It'll be a copy and I'm sure things will go wrong". "Rubbish". I'm on leave and I get a call "None of the antennas has passed patterns or cross-pol !! The manufacturer says they were installed wrongly". That one cost a few pennies. But what do I know.

Dave