AirPort Extreme

My suggestion would be to first check the speed over an Ethernet connection on the second AirPort Extreme in two different ways.

1. Temporarily disconnect the Ethernet cable from the second AirPort that connects back to the main AirPort and connect an Ethernet device like a PC or Mac to the Ethernet cable and run a speed check that way. The results should be very close to the same speed that you obtain when you connect an Ethernet device to the "main" AirPort.

If they are not, then there is a problem with the Ethernet cable itself or the Ethernet port on the second AirPort may not be functioning correctly.

If the speed checks out OK when you run the 1. check above, then........

2. Connect the Ethernet cable back to the second AirPort Extreme and then connect an Ethernet cable to one of the three LAN <---> Ethernet ports on the AirPort Extreme and check speeds that way. The speeds should be the same.

We ask you to check the Ethernet speeds and connections because you cannot troubleshoot a Wi-Fi connection without first checking to make sure that the Ethernet connections are working correctly.

Another thought would be that Apple discontinued the AirPort Extreme over 4 years ago, so you likely bought either a "refurbished" AirPort or a "used" AirPort. I suppose it is possible that the AirPort could be "new", but it would have been sitting in a warehouse for 4 years in this case.

A few thoughts from the screenshots:

• AirPort Base Station & wireless network names, typically work "best," if they are 16-characters or less and don't contain either special characters or spaces. Regardless, the Wireless Network Name should be identical for each base station in order for a roaming-type network to function properly.
• "Back to My Mac" is a service that Apple discontinued years ago. I suggest that you remove it from your AirPort's settings.
• "WPA/WPA2 Personal" is less secure than "WPA2 Personal." I suggest reconfiguring your wireless network on all of your base stations to use the latter type.

How do you have the second AirPort Extreme configured to extend the first one? Specifically, what do you have the Network Mode setting set to? It should be "Create a wireless network" for roaming mode. Screen shots, of the settings in the AirPort Utility, would be helpful.

I was expecting to get the same speed from both routers but the primary is around 3 times as fast as the extension.

Although it might be surprising, the extending AirPort Extreme should not be set up to "Extend a wireless network". That setting would only be correct if the extending AirPort were connecting to the main Extreme using a wireless connection......not Ethernet.

So, as forum expert Tesserax mentions, the second AirPort Extreme should be set up to "Create a wireless network" that uses the exact same name, security and password as the "main" AirPort Extreme. Additionally, the second AirPort needs to be set up in Bridge Mode, which Apple calls "Off (Bridge Mode)".

Even if the second AirPort is set up correctly, there are no guarantees that a Mac, iPhone / iPad etc, will automatically "switch" to pick up the signal from the closest AirPort when the device changes locations. Check to make sure that the device is connected to the closest AirPort when you want to perform any speed checks, etc.

> since the cable wasn’t long enough I used a coupler to extend it

Thanks for the update. Now I know to be wary of ethernet splitters and also couplers.

"Ethernet Splitter. Let’s start with the thing you were probably most tempted to just run out and buy when looking to transform one Ethernet connection into several. (Hint: don’t do it!)"

https://www.maketecheasier.com/ethernet-switch-vs-hub-vs-splitter/