Thank you for the image of your signal report. I had hoped for the link to the report or its ID number so that I could click on a callsign for additional information, but I think the image will do for now.
I don't think the short added cable is the source of the problem.
If the original coax is damaged or defective, new coax would help.
No, don't add an amp; WVUT is already strong enough to cause overload.
WVUT is weaker with the antenna inside. But, we still don't know if the cause of the problem is because WVUT is so strong, or if the connection between the outside antenna and the TV is defective. You could try adding an attenuator in the coax.
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You have a difficult location for OTA reception. Your signals are in different directions and there is a great difference in signal strength between the weakest and strongest signals. The strong signals make it more difficult to receive the weakest signals.
Please tell us which RCA antenna you have and the direction you have it aimed. Here is a photo of the antenna I have. I have it pointed 10 degrees off North going East. Pointed to Terre Haute. It is only the Stations of WTWO, WAWV, and WTHI I want to receive. When I was testing the antenna inside. I was getting all 3 of these stations. Even WTHI which should be the most difficult. But now with the antenna mounted off side of tower. None of the stations come in.