I’ve got an end fed half wave for 40m strung up in the loft area of my garage, but the way my attached garage works, it’s dry walled up there. I’m having trouble being heard and I’m wondering if this is part of the problem.
Another thing that is working against me is my power supply isn’t delivering max power to my G90, so I need to fix that too!
Yes any obstacle will affect performance. Indoor antennas especially when using a compromise antenna like yours and QRP power is never a very fun exercise.