Poor FM Reception

Solar panels will generate radio frequency interference (RFI) when the invert  DC voltage to AC.  This will disrupt broadcast radio frequencies.   The panels themselves represent an additional layer of material to block or reduce indoor antenna radio frequency reception.  Potential solutions:

1. As you indicate, go with an outdoor antenna.  Install the antenna above the highest point of the panels on the roof.  Locate the antenna as far as possible away from the inverter.  
2. Assure solar panel wiring is shielded.   On simple and inexpensive solution is to place ferrites on the wiring between panels, and the leads in and out of the inverter.  

I am a Ham Radio operator. There is no interference from the solar panels and It would show up much greater on the lower Ham radio frequencies,

I live in a remote area where there's few stations and the only operate on 5,000W daytime and 500W at night. Those expensive Term antenna's are no good but I found an amplified rabbit ear after trying 4 other antenna's for my vintage McIntosh MR-71 tuner that works great. Home Depot online. $18 free shipping. It is a NAXA

I live in a remote area where there's few stations and the only operate on 5,000W daytime and 500W at night. Those expensive Terk antenna's are no good but I found an amplified rabbit ear after trying 4 other antenna's for my vintage McIntosh MR-71 tuner that works great. Home Depot online. $18 free shipping. It is a NAXA