RF signal boost

Hi. I have a random question. I have a Petsafe pet door that operates on a RF frequency that I need to somehow boost. The door itself operates on 4 "D" batteries. I have opened the unit and have access to the antenna wire but am unsure what to use or do. ANy thoughts?

 

Petsafe Electronic pet door

Thank you for responding! I have a dog and a cat and I want the dog to be able to come into the basement but not the cat. The cat is a great hunter and likes to bring his "kills"(mice, rats, birds) inside and play with them until they die. Sometimes these animals make it to a secure location and then die and our entire house smells. We came up with the pet door as a solution but for some reason it won't work in the only location that it can go. If you take the door out of the hole and move it to another location it works fine. I have shut off all of the wi-fi, cordless phones, appliances, power, etc. and still no joy. I opened the unit and found the antenna wire, which is pretty long, and actually let it drape on the outside of the unit and it still wouldn't work in that location. My only other thought was to boost the signal somehow.
The model of the door is PETSAFE PPA11-10709.
I would appreciate any insight you might have and if there is nothing to be done I totally understand and appreciate your time!