MIMO multiple antenna distances?

pyropetepete

pyropetepete

pyropetepete

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Got a TP-Link TL-WA801ND http://www.tp-link.com/en/products/details/?model=tl-wa801nd, it's has 2 antennas and use this MIMO http://en.wikipedia.org/wiki/MIMO

I've tried as much as i can too see is there is a required distance between the 2.

Reason being i have been offered 2 TL-ANT2415D http://www.tp-link.com/en/products/details/?categoryid=217&model=TL-ANT2415D for less than £30.

My idea is to use these two to replace the 2 4dbi's that came on the unit. To use really short, 12'' or less pigtails from the AP to these, then stick the AP in a sealed box, mount it all on a T frame and stick it outside (my new gaff is 45ft high) so i could cover over nicely.

But can't find anyhting online to say how far the aerials need to be apart under this MIMO tech.
 
Pete, no need to worry about the distance between the antennas as such because they are not connected together because the antennas are on different WiFi transceivers in the unit.

One antenna operating on one channel, and the other on a second channel. This allows the unit to transmit and receive data at the same time so increasing the throughput on the WiFi.

It would matter if you were phasing the antennas together to produce a higher gain array but you are not doing this so there is no worries here.

Cheers,

Tezabeza
 
Spatial multiplexing makes use of the same frequency but uses antenna diversity to allow multiple streams to be used at the same time. There are also other uses to MIMO operation that use a single spatial stream but multiple transmit antennas to increase the received signal strength, and this obviously uses the same frequency as well.

So antenna spacing is important, and although my project on 802.11n I did for my degree didn't cover antenna spacing I believe the correct distance is a multiple of the wavelength which if I remember right means a multiple of ~6cm for 5GHz, or around 12.5cm for 2.4GHz WiFi.
 
Sorry it's short boys, I'm out onsite and trying to use my phone. What if I measure what's on the back of the unit as is and copy that? Also these are 15dbi. What's the real gain? Tez I tried mailing. What's the best cable to use here? Can you sort me out?
 
Sorry to bring this back up, my aerials come today and going to build the frame and mount tomorrow.

I've found some info on CISCO to say as long as it's not less than the wavelength or 4x more it's fine for what what ever.

So the back of the AP it's 130mm/13cm

Should i keep that or doubble it, so 260mm/26cm apart.

I think the 260mm/26cm looks best, works best for moutning it etc, it's only 2x the wavelength as well.
 
You can keep it, or double it, it wont make much difference, as long as it is a multiple of the wavelength it'll be 'tuned' (I'm sure there is a better term for this effect, but my tutor always used to just call it an antenna being 'tuned' to the frequency). Although my calculations make 130mm a little too wide for 2.4GHz so if you wan't to try and be more precise use 12.5cm or a multiple of that (so 25cm if you double it), although that's only if you really care, you can use 130mm or 260mm if you want, it wont make too big a difference anyway.
 
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