Signal lobes of ZenWiFi-XT8's antenna?

[toaruScar]

This diagram is a cross section my home. There're 3 ZenWiFi-XT8 routers in the diagram. They're at the same "depth" on the diagram. The facing of the asus logo is represented by the vectors, with guest room router pointing left, bedroom into the page (that tiny "⊗"), and garden right.

+                                   Rooftop Garden                        +
|                                   Router -------> →                     |
|                                                                         |
+-------------------------------------------------------------------------+ Extra thick
+-------------------------------------------------------------------------+ Floor
|                        |                                                |
|                        |                                                |
|                        |                                                |
|                        |                                                |
|                        |              Bedroom                           |
|                        |              Router -> ⊗                       |
|                        |                                                |
+-------------------------------------------------------------------------+ Floor
|                        |                                                |
|                        |                                                |
|                        |                                                |
|       Guest room       |                                                |
|       Router ------> ← |                                                |
|                        |                                                |
|                        |                                                |
+------------------------+------------------------------------------------+
                    Some wall

The garden router is not wired, so it needs a wireless backhaul.
My problem is that the garden router (the one on the top) always tries to connect to the guest room router (the one at the bottom), rather than the bedroom router (the one in the middle). But empirically speaking, it should connect to the bedroom router.
I begin to doubt if my effort to "correct" the network topology by forcing a wireless backhaul between bedroom and garden routers is worth it? Is the system try to tell me something? Could this be because for the XT8 series, the signal is the weakest right above (and below) it?

 

[L&LD]

If your antennae are pointing straight up, yes, the signal directly above and below is highly attenuated.

Antenna radiation plots - What do they mean?

Antennas are a fundamental component of any wireless RF solution and this article helps to understand how to read the test patterns and what they mean.

www.rs-online.com

 

[ColinTaylor]

Given that the antennas are a mixture of vertical and 45 degrees (promoted as a feature) this would create a blind-spot directly above and below the routers. We can't tell from your diagram how the routers are placed relative to each other in the z-axis. Turning the garden router by 90 degrees might be sufficient if the bedroom router is not directly below it. Otherwise in theory moving the garden router towards the right hand side of your diagram should bring its antennas into alignment with the router below (assuming the Asus logos are facing the viewer of your diagram).

 

[toaruScar]

We can't tell from your diagram how the routers are placed relative to each other in the z-axis.

I updated the diagram with the facing of the router. I didn't realize the orientation of routers plays an role in this.

Turning the garden router by 90 degrees might be sufficient if the bedroom router is not directly below it.

Do you mean pitching the router 90 degree up, so that asus logo is pointing up?

 

[ColinTaylor]

Do you mean pitching the router 90 degree up, so that asus logo is pointing up?

No. If you are looking down on the router from above and the router is aligned north-south, try turning it so that it is west-east. It might not make any difference but it's worth a shot.

 

[Cain]

Which side of this router would have the strongest signal, the front/back or the sides??? Anyone know??