Using the equipment that I have available, I was able to add analog channel 65 to my OTA channels:
Obviously, the TV must be able to receive analog channels as well as digital channels.
The modulator is leaking through the port to port isolation of the splitter used as a combiner. The attenuator, port to port isolation, and LTE filter reduce the modulator signals reaching the antenna.
A preamp below the LTE filter, if needed, will increase the isolation. The attenuator can be increased to bring the modulator signals down to -9 dBmV; the snow begins at about -15 dBmV.
Grounding the coax shield will make the attenuator and LTE filter more effective.
I have the equipment to measure the modulator signals that arrive at the antenna; most user don't. If they are below the Thermal Noise Floor (for a 6 MHz bandwidth TV signal) at -106 dBm (-57 dBmV) , it is probably safe, as far a causing interference is concerned. Without the CM LTE filter, the modulator would be considered an illegal unlicensed transmitter.
These are the measurements for the splitter as combiner that I used:
IN Modulator Port: +1 dBmV
OUT Antenna Port, TV Port not terminated: -6 dBmV
OUT Antenna Port, TV Port terminated w/75 ohms: -23 dBmV
The attenuation of the CM 3201 for channel 65 is 69 dB
That would make the channel 65 modulator signal at the antenna -75 dBmV (-124 dBm) with the TV port unterminated
and
-92 dBmV (-141 dBm) with the TV port terminated.