Total posts : 45366
Ken is right, of course, about the quality of a radio receiver having much to do with how adjacent signals are handled, but there are antenna issues I have found…
Part 15 is so weak compared to the upper-kiloWatt full power stations, if their signals are near yours on the dial..
Your transmit antenna very likely receives a huge dose of kiloWatt energy that can back-flow into your transmitter and actually appear as noise on your signal.
The radio tuned to your signal also is receiving more power down the antenna from the adjacent signal than from yours, so it may leak in.
This also happens on AM if stations are nearby both on the dial and within a mile or so.
A very good practice to avoid this, if possible, is to find a frequency whose next-door-on-the-dial stations are far away geographically.