How to extend the scope of screening?

I volunteer for approximately 1 year, I really enjoy the experience of tracking aircraft in the Amazon jungle, but I believe the range of my ADS-B equipment is small. The antenna is installed in a high, free and interference-free location and I note that the aircraft are only visible very close to my location. How could you proceed to increase the radius of tracing, if at all possible?

Which type of Flightfeeder do you have?

Flightfeeders should normally not be modified.

Might be that you have water ingress into your cable as your performance seems to be decreasing.
Also even remote places have mobile phone service now, which can be bad for reception when the mast is close.