I think a 40m EFHW might be your best option. If you can keep the antenna up for extended time, you can make a window bulkhead with some wood or you can buy one of the fancy ones MFJ makes. Otherwise, you could just run your coax to the antenna and then tie (with parachord or similar) the ends to the tree, etc and something sturdy inside.
A more expensive solution would be to use a magloop inside. You could also get a vertical and put it in the yard and run coax to it.
I think a 40m EFHW might be your best option. If you can keep the antenna up for extended time, you can make a window bulkhead with some wood or you can buy one of the fancy ones MFJ makes. Otherwise, you could just run your coax to the antenna and then tie (with parachord or similar) the ends to the tree, etc and something sturdy inside.
A more expensive solution would be to use a magloop inside. You could also get a vertical and put it in the yard and run coax to it.