Number of antennas on Wi-Fi Range Extenders


I want to get a 2x2 MIMO dual-band device I can use as a wireless range extender.

Since I intend to put OpenWrt on it anyway, I guess it doesn't really matter whether I buy a device that is actually designated by its manufacturer as "Range Extender" or if it's a Wi-Fi router or Wi-Fi AP.

However, here is where I need some advice:
Looking at pictures that show the innards of several 2x2 dual-band Range Extenders made by TP-Link (and also their official spec sheets) it appears that those Range Extenders only contain two physical antennas, while any 2x2 dual-band Wi-Fi router I have ever dealt with had four antennas (2 for 2.4 GHz and 2 for 5 GHz).

I guess if using just two antennas for a 2x2 dual-band AP did not carry any performance penalty, then manufacturers wouldn't generously put four antennas on their 2x2 MIMO dual-band Wi-Fi router models, would they?

So I am wondering what's the deal with those Range Extender models that share only two antennas for 2x2 dual-band operation? How much does it affect performance?

(I know this hardware question is not specifically related to OpenWrt, but I don't know where else would be a good place to find someone who may have the knowledge to answer this)

A range extender is a duplex radio link. It just moves the data along.

Usually the 4antenna devices is 1antenna for 2,4GHz. 2 antennas for 5GHz beamforming and 1 receiver antenna 5GHz for radar protection (DFS).

There are basically two alternatives:

  • multiplexing the signals from one 2.4 GHz and one 5 GHz PHY into one dual-band antenna (and doing thise twice, for 2x2)
  • 2.4 GHz just going to PCB antennas, instead of being connected to dedicated ones

Purpose built wifi extenders usually need to be cheap(er than a wifi router), so they are designed accordingly (weaker/ older SOCs, questionable antennas, …).

Thanks for the replies.

It must be the first of the two alternatives that slh mentioned.

The specs sheets clearly state "2 antennas" for 2x2 dual band range extenders.

I've also checked more pictures of PCBs from dual-band range extenders other people have posted on the Internet and I am seeing that the RF signals of both Wi-Fi chips (usually one "SoC" that contains the CPU and one Wi-Fi radio and then another Wi-Fi-only chip that handles the second band) are routed to what I believe is a "diplexer" whose output pin is then connected to the antenna. On TP-Link's range extenders that diplexer is a white 6-pin package with a brownish rectangle on top of it.

But I still haven't been able to find any information about how much such a solution affects performance. I can't quite imagine that this could possibly work as good as separate antennas.
So I guess I will just go for a device that has separate antennas.