please help to novice.
in RB711GA-5HnD specification written that it has 2 chains, it means:

1. that I must connect two identical antennas (like this),
2. or I must connect only dual polarization mimo antenna (like this),
3. or I might connect one antenna (like this) in chain0 and it will be work?

What correct decision, what wrong decision?

all the options work, important is what you need it for

all the options work, important is what you need it for

If I correctly understand, in RB711GA-5HnD two chains used for spatial diversity.
so what kind of main benefit or disadvantage will be for these types of antenna's connections?

maybe somebody can give a link where I can read about routerboard hardware and antenna's use

you should use google to learn about all tipes of antennas and second chain is not for spatial diversity but it can be used that way.

I rephrase the question, what is purpose of TX in 2 chains in the RB711GA-5HnD, but only with 1 stream?

I rephrase the question, what is purpose of TX in 2 chains in the RB711GA-5HnD, but only with 1 stream?

To get full speed of 802.11n. Only with two antennas, or dual pol antenna, you can get near 300Mbit wireless speed in 802.11n

I rephrase the question, what is purpose of TX in 2 chains in the RB711GA-5HnD, but only with 1 stream?

To get full speed of 802.11n. Only with two antennas, or dual pol antenna, you can get near 300Mbit wireless speed in 802.11n

I little bit confused, in the brochure for R52n-M (for example) written about 2Nss and speeds up to 300Mbps, and in the brochure for RB711GA-5HnD have written only about MCS7 and not written "Data Rates".

So, if I correctly understood all routerboard with D in its name (or with two chains) has been working with 2Nss?

300Mbit is only possible with 2 chains. R52n-M has two connectors.

300Mbit is only possible with 2 chains. R52n-M has two connectors.

and why in the specification for routerboard has been written mcs7, but if 2Nss then it must be from mcs8 to mcs15?

Where did you see this? From the R52n-M datasheet:


2Nss: 270Mbps @ 800GI, 300Mbps @ 400GI (Max.)
MCS7 20MHz -77 16

Where did you see this? From the R52n-M datasheet:

2Nss: 270Mbps @ 800GI, 300Mbps @ 400GI (Max.)
MCS7 20MHz -77 16

http://routerboard.com/pdf/330/rb711G-5.pdf
only mcs7, and no one words about 300Mbps

What did you expect to see there? MCS data rates are the same for all 802.11n devices
You can go and see the MCS numbers here: http://en.wikipedia.org/wiki/IEEE_802.11n-2009

What did you expect to see there? MCS data rates are the same for all 802.11n devices
You can go and see the MCS numbers here: http://en.wikipedia.org/wiki/IEEE_802.11n-2009

if RB711GA-5HnD support 300Mbps throughput, I expected to see mcs15

Of course it supports MCS15 because it supports 802.11n

You are asking something like "Does this car have wheels", and I am telling you "If it's a car, it has wheels, its logical"

Of course it supports MCS15 because it supports 802.11n

You are asking something like "Does this car have wheels", and I am telling you "If it's a car, it has wheels, its logical"

yes, but if I see picture of this car in a store without wheels, I ask myself, do i have to buy wheels separately

anyway, thanks for your answers.

All cars have wheels. All RouterBOARDs which have 802.11n support, support all MCS depending on number of chains. One chain - MCS7, two chains - MCS15. Read the 802.11n standard please. This is normal operation, and datasheets shouldn't include common knowledge that applies to all devices.