@LadefogedT 

You can try swapping one of the satellite units with the main Deco to see if the main Deco could be giving the slow speeds. I'm assuming the wireless signal is likely just weakening having to go through floors. 

You are able to wire Deco units together to help improve the signal. You can have both satellites wired to a switch, then the switch to the main Deco. You can also wire the second unit to the first, then the first to the main Deco.

@Tony 

Thanks for your answer. Much appreciated.

I just do not understand it. The main deco is placed right next to the router. No distance to cover. If I measure the speed in the app, the speed is fine. When I measure the speed in another app. The difference is HUGE. I do not understand the loss of speed?

Can the setup be wrong in some way? How do I check if the main deco is actually the one next to the router?

Thanks,

Thomas

@LadefogedT 

The main Deco is always the one wired to the modem. What you can also do is to go into the Deco app, tap on the globe icon then tap on the Deco units to see what is connected to what. 

@Tony 

Hi Tony,

If you look in the image the main deco is wired to the router. Still I see a HUGE drop in speed when measuring the speed. Why? Measuring in the Deco app the speed is 802/520 mbps. When measuring the wifi connection on one of the slaves the speed is only 61/33. This cannot be right! And it is not like the main and slaves are far apart. They are right on top of each other with one on each floor.

What is wrong in the setup? The main is (as mentioned) wired directly to the router. The two slave Decos are wireless.

Do I need to wire the main to one slave and from this slave to the last slave...?

Thanks for advising.

Thomas

@LadefogedT 

Wireless signal severely degrades when going up or down the next floor.

My previous post mentions using the Deco app to see where your device is connected to, please see if the phone is connected to the main Deco. If it is, swap the main Deco with one of the satellite units (https://www.tp-link.com/us/support/faq/2400/). Then look to see if your Deco speeds improve, also disable the Wi-Fi on your router to make sure the router is not interfering with the speed.

Doing the speed test in the app is the Deco measuring the speed that it is getting from the Ethernet cable so that is fine.

Another thing you can try is to get a computer and wire to every Deco node to see what speeds they get, not using Wi-Fi.

@Tony same problem here when I put my WiFi device right next to the main deco m9 plus. Samsung Note 10+, new i7 10th gen laptop, all connected 5Ghz and anything WiFi 2.4Ghz is the same or worse.

Here are my ridiculous results from just the last hour, about 800-900Mbps download from wired device, but only 50-150 from wireless devices:

Here's what I used to get 6 months ago with the same equipment, when I just purchased the deco M9 Plus. nothing changed other than deco firmware updates:

I'm on flat apt, no floors, same results even when one unit is off, all tests were taken within 20cm of the main unit. Here's the info: Deco M9 Plus two units, Firmware 1.2.11, build 20190926, rel 55727.

Furthermore, some of my WiFi devices keep getting randomly disconnecting from the WiFi and losing signal while in use, auto reconnecting after 10-15 seconds. Only the wired device keeps getting strong stable solid connection, so definitely something WiFi related.

Tried all QoS options, tried disabling antivirus filter, any other suggestion maybe?

Thanks

@Simerotic 

Past users have factory defaulted their Deco units and reported speeds returning.