It would appear that by default the emonSD-30Oct2018 sets up the RPi 3B+ WiFi as an access point. I am using Ethernet cable, so I want to disable the WiFi for security reasons.
To completely disable the onboard WiFi from the firmware on the Pi3, add
in /boot/config.txt .
There is also an overlay for disabling onboard bluetooth :
pi3-disable-bt . If you want to disable both wifi and bluetooth, you need to add these 2 lines :