A loose F connector (or an improperly installed one)can allow leakage,or a
corroded connector;the corrosion acts like a diode,creating harmonics from
the many signals on the cable.One of the cable channels may have the
same,or be close to a frequency used by aircraft.

Tha amp itself could have problems,perhaps overdriving an internal stage
enough to cause EMI radiation.

cheap TV amps (including Gemini as the OP stated) were notorious for
RFI at one time. I think they have been forced to provide a cleaner
product now.

Enuf