Polish up that Sense of Wonder: Nancy Etchemendy, Stranger from the Stars (New York: Avon, 1983).
I'm puzzling over this book because it has all the right ingredients, but somehow the cake sank in the oven.
Ruthie Keag lives on a ranch. She has two best friends, Kate the bookworm and Tom the town badboy. She is fascinated by electronics and has a table full of equipment in her room, but is also girl-soppy about her horse.
One day she sees an odd looking stranger out in the range, and when she returns, Tom is trying to kill him. She scares Tom off.
As the story progresses we learn the stranger is an anthropologist from an inter-planetary culture, crash landed on the planet by a member of the crew who stole an artefact of Earth and killed two other crew members to hide what he had done. Tom has taken the wrong side, but knowingly. A kid from the wrong side of the tracks, he has aligned with his alien in the hope he'll be taken off planet.
One of the key issues will be Ruthie getting the alien's communicator to work again, and this is pretty effective--Ruthie lines up all the damaged communicators, decides which is least broken and then works through it, comparing each part to the parts in the other more damaged models until she manages to assemble all the working components and it functions.
The communicator brings rescue and the aliens leave. Tom wonders if they will keep their promise to come back.
One noteable difference to some other books is that by the end none of this is secret: the whole town knows and the men of the town are involved. The recursion is mostly that we have no sense of wider consequence rather than that the town is left utterly unmarked.
But what really bothers me is that somehow, Nancy Etchemendy managed to make this story dull. There is no sense of wonder. What I think went wrong is that she desperately wanted a hero who was a girl and was scientific, but was terrified of putting girls off with a "nerd". The result is that there is a constant mild sense of apology for Ruthie's interests, and they are kept coralled and confined to that table. When she isn't in her room, Ruthie doesn't think about science. We may be sf fans but you could never imagine Ruthie at an sf convention.