Combining Dish Modulated signal with Comcast Digital

[shakti]

I am trying to combine my DISH 522 TV2 feed which can be modulated to any range 21-69 or 73-125 with a Comcast digital service feed (since I have only one wire run to two of my TV's upstairs) but have no luck. My TV has a digital ATSC/QAM tuner along with an analog NTSC tuner and I first connected the Comcast signal feed directly to the TV and did a scan for Analog and digtal signals. It found about 300 (well most of them are scrambled). With this info I found a range that comcast does not broadcast or send any programming. this happened to be between 70-75 and then 90-95 and then 120-125
I set my DISH 522 TV2 feed to be modulated to the various freq in this range (cosnidering a 5 ch gap) but I cannot get my TV to tune to the DISH feed. I managed to get some signal on CH125 but it was very grainy/snowy

Any insights, is the Comcast signal corrupting the Dish 522 RF feed

Any insights would be helpful