Here is an issue with at least Mac OSX v10.13.4 and 10.14.1. Not sure if it affection iOS devices as well.
The problem was still occuring on Mojave in 2018 but maybe fixed now.
Macbook location services does a full wifi scan every minute to get your location. This scan can cause interference and network latency between other nearby devices (even on separate wifi network).
The source of the problem was locationd and to fix the spikes go to Settings -> Security & Privacy -> Location Services -> (System Services) Details -> uncheck “Time Zone & System Customization”
It is checking time zone every minute or so.
Turns out Google Earth is a QT app. QT has a “bearer” plugin which can frequently request wifi scans, killing network performance. See:
Until Apple and QT developers fix, possible workarounds are setting the QT_BEARER_POLL_TIMEOUT environment variable to -1 or disabling the wlan bearer plugin altogether
in the QT app.
(for Google Earth Pro: “sudo chmod 0 /Applications/Google\ Earth\ Pro.app/Contents/plugins/bearer/libqcorewlanbearer.dylib”)