This small change more than tripled my positions reported and more than doubled the number of aircraft seen.
Obviously this is an unscientific test since the data varies from day to day, but the change was significant and I’m comparing to the same day-of-the-week from the previous week.
I added an approximately 3 inch (75mm) ferrite iron ring to my setup. I wrapped the USB cord to the receiver through the core multiple times as well as the power cord to my raspberry pi.
I left as little remaining cord as possible between the ferrite ring and the receiver so the cable couldn’t act like an antenna.
The core I used was similar to this:
ebay.com/itm/73mm-x-38mm-x-1 … 51ad695bdc
I am also getting a slightly larger reach. (5-10%)