While troubleshooting my new TV wifi connection I set my wifi router to a discrete 5GHz SSID. This was to aid the TV to find the faster 5GHz connection. Before that I gather my AirPort Extreme wifi router was set to offer up both 2.4GHz and 5GHz bands simultaneously.  All my devices worked well getting respectable download times on a 600 Mbps account. As soon as I turned on the 5GHZ with its own SSID, all my devices appeared to get dramatically slower connections as follows:

Imac 630Mbps > 150Mbps

iPad Pro 400Mbps > 75Mbps

AppleTV v4 250 Mbps > 60Mbps

I have had my Airport router set to automatically offer 2.4Ghz and 5GHz for years and got very good speed on Shaw Internet. I am now assuming my devices tended to connect to the 5GHz band.

I contacted Apple and they said putting a separate name to the 5GHz band should not interfere with the 2.4GHz band. Even though it appears that by adding a separate SSID for the 5GHz band that I would then have to manually direct my devices to which band to operate on.

After a bit of troubleshooting including modem and router reboot the problem persists. This leads me to think that over the years devices have been connecting to the faster 5GHz band on my wifi router automatically, thereby getting maximum speeds. Directing my devices to the 2.5GHz band I get much slower speeds. This leads me to conclude my my 2.4GHz band is not performing well at all.

Any suggestions about improving speeds on the 2.4GHz band or do I need to be on the 5GHz band for optimal speeds nearing 600Mbs on the Shaw system?