Thanks for the video showing three channels and signal quality, which looks more like signal strength.
KCAL real channel 9, NM 6.4 dB, weak signal on RCA and pixilation
KNBC real channel 36, NM -10.2 dB, strong stable signal
KABC, real channel 7, NM 8.6 dB, weak signal on RCA with pixilation and dropout
Is KTTV Fox affected? Is KCOP affected?
I don't think it is cellular transmitter interference which is more likely to affect UHF before it would affect VHF reception.
In your video VHF reception is affected, but not UHF. There might be another reason why VHF is affected but not UHF that is still unknown.
You should consider possible sources of VHF interference.
If the antenna is outside, the coax shield should be grounded with a grounding block that is connected to the house electrical system ground with 10 gauge copper wire for electrical safety and to
reject interference. For further compliance with the electrical code (NEC), the mast should also be grounded in a similar manner to drain any buildup of static charge, but the system will not survive a direct strike.
Notice that reject interference is in bold type. You might have a local source of interference like power line noise, strong FM signal overloading preamp, strong FM signal not sufficiently attenuated by FM filter in preamp, or EMI from a neighbor's solar system inverter.
I suggest you listen for electrical interference on an AM portable radio tuned to a vacant frequency first at the low 550 kHz end and then at the high 1600 kHz end. A portable radio tuned to FM doesn't work as well, but a portable radio that can tune VHF aircraft control frequencies will work because that is AM.
