Bluetooth range

I have Airpods which work a treat on my iPhone 7+. I can circumnavigate my 3 bedroom house and not disconnect from the phone whilst it is sitting on the same desk as the Mac Mini which is a different story. Even whilst sitting at the desk with the Mac 1.2 metres away, it will drop out. Same Airpods.

I have noticed, when pluging other devices into USB, the range is effected. Sometimes I have trouble with the BT keyboard as well, when plugging an external drive in. Any solutions?