Wifi-2-Wifi extender with OpenWrt (and old TP-Link routers)

I want to improve the signal of my home Wifi network in some rooms where the current Wifi signal is very weak.

Before buying a ready-to-use Wifi extender, I decided to try to improve the signal by using and setting up a couple of my old and usunsed routers.

Now, I have two old and unused routers:

TP-Link TL-WR841N/ND and TP-Link TL-WR740N

I already tried extending my Wifi by doing the following:

  1. Installed the latest OpenWrt (OpenWrt 18.06.9 r8077-7cbbab7246) version on the TP-Link TL-WR841N/ND
  2. Connected to my existing Wifi router's network, let's call it MYNET, from the TP-Link TL-WR841N/ND (client mode)
  3. Created an AP network (master mode), let's call it MYNET2 on the TP-Link TL-WR841N/ND

Now, when a device connects to MYNET2, all works good, but the upload/download speeds are very, very low. I suspect the channel lock forced by OpenWrt on the TP-Link TL-WR841N/ND's second (MYNET2), network, is what causes all of the MYNET and MYNET2 traffic to constantly collide as it exists/enters the antenna(s).

The next thing I will try (unless someone here helps me achieve my goal without having to resort to a second router) is connect the two routers (the TP-Link TL-WR841N/ND and the TP-Link TL-WR740N) with an ethernet cable, and use one of them to connect to my existing Wifi network (client mоde) and the other to serve as the "extending" Wifi network my devices will be connecting to.

Any recommendations/help/guidance on how to properly do it (with only one router, perhaps?) will be greatly appreciated!


P.S. I cannot connect any of the "extending" routers to my existing router via a cable, hence the need to repeat the Wifi signal in some other, but efficient way.