@westover69 

In Deco mesh, Satellites will strongly prefer to connect to Main Deco. If you place Main Deco to the basement, second floor Satellite Deco will try connecting to it even if WiFi link between them is weak. That will negatively impact speed for any device connected to second floor Satellite Deco.

If your M4 are on firmware 1.58, you can't override that Satellite Deco preference.

Note that even if your second floor Satellite Deco connects wirelessly to now Satellite Deco on ground floor, second floor speeds will be half of ground floor speeds because of an extra hop to Main Deco in the basement. This is not Deco mesh defect, this is limitation of WiFi mesh technology. Each hop cuts speed by half.

For that reason, in house like yours the optimal placement of Main Deco is on the ground floor in the middle of the house. With Satellites in the basement and on the second floor. What you have now.

Can you explain what are these "impending changes" that will force you move Main Deco to the basement? I have cable modem/router from my ISP, it is located in the far corner of the basement where coax cable enters my house. My Main Deco is in the middle of the house, on the ground floor. I have Satellite Deco on the second floor connected to Main Deco wirelessly.

My setup is very similar to yours. In my case, Main Deco connects to ISP cable modem/router with long Ethernet cable that passes through walls and floor. No issues with having everything like that.

  @Alexandre. 

Thank you so much for the great explanation. I have attached this schematic to describe the impending changes. The left hand side describes my current set-up. The right hand side describes the proposed changes. Essentially, I am getting a new ATA that has to be connected via ethernet to what I hope will be a more efficient (newer) cable modem.

I think you have provided me with the solution which is to run a long ethernet cable between the basement and main floor which then allows me 2 options:

a) move the Deco Main (only) to the main floor, or

b) move the new cable modem and Deco Main to the main floor

Thank again for your help!

  @westover69 

Because you have coax cable coming to the ground floor from the basement, here is another option for you to consider. With the pair of MoCA adapters you can create Ethernet link over coax cable. You can connect Main Deco on the ground floor to one side of that link and cable modem in the basement to another side of it.

You will need to do a research on that topic and find if that works for you, and it'll be more expensive than just long Ethernet cable. Still, it is an option.

  @Alexandre. 

Thanks for suggesting MoCA adapters. It is a nice option but as you pointed out, they are pretty expensive compared to running ethernet cable. 

In my research, I came across this fairly inexpensive MoCA adapter (Vision KMC 1000). Please let me know if you think this would do the job.

VISION KMC 1000
The KMC1000 is a high-speed bridge that in conjunction with router, delivers Ethernet networking access anywhere you have a coaxial port. MoCA technology guarantees the distribution of HD and ultra-HD content around the house over coax.  With support for the latest MoCA 2.0 standard, the KMC1000 delivers wired speeds up to 500 Mbps, more than enough bandwidth for HD video, online gaming, and other demanding applications.  You get the reliability and performance of a wired connection over coax, without the expense of wiring the home for Gigabit Ethernet.

Specifications

Main Chipset:  BCM6803 (MIPS-M4K@200MHz, 384KB IRAM, 128KB DRAM, 32KB shared memory)

Memory: Flash: 8MB SPI (NOR)

Spec:   MoCA 2.0 (Interoperability to MoCA 1.1 / MoCA 1.0)

Radio Frequency :   1125MHz ~ 1675MHz (Extended D Band)

MAC Rates:  400Mbps

PHY Rates:  630Mbps

Rear:  1 x Cable In 1 x Reset Button 1 x LAN Port

Top:  1 x PWR LED 1 x MoCA LED (MoCA Link / Post Failed)

Power:  AC 110V

  @westover69 

MoCA adapters will be expensive, but it is best alternative for Ethernet cable if you can't lay it through the house and it is already cabled with TV cables.

I can't endorse specific adapters, because you will need to research if they are worknig for you. I would suggest to look at following:

1. Must be at least Moca 2.0. If you buy MoCA 2.5 adapters that promise faster speeds than gigabit, make sure they come with Ethernet ports faster than gigabit, othewise spending onMoCA 2.5 is waste of money;

2. MoCA adapters will work for sure if coax cable is idle, meaning it is no longer used to transfer TV signal. If TV cable will be shared between both TV and MoCA/Ethernet, you'll need to check compatibility.

I found useful article for you, but external links are not allowed here. You can find it by googling for:

How to Set Up and Use MoCA Adapters

Learn how to install and start using MoCA Ethernet over coax adapters for Internet connectivity throughout your home.

On techreviewer Web site.

  @Alexandre. 

Many thanks again for all your invaluable technical advice.