Fox was the one I was worried about. Its usually 20ish dB on a single TV. I feared adding a regular splitter would leave me with 20dB-3.5dB = 16.5dB or a very margin signal. Was hoping the CM3412 would overcome that but I guess not.
If you have a 20 dB SNR with one TV, then the 3412 should have compensated for the split. You can add an attenuator if the 3412 11.5 dB gain is a little too much for the tuner, but I agree with chinadog, you shouldn't even need the 3412.
DB8e > 7777 > coax 60 ft > grounding block > power inserter > 3412 > TVs
In theory, you shouldn't even be able to receive WUTV Fox on real channel 14, but tvfool reports are known to be wrong for 2Edge signals. It has a Noise Margin of -31.7 dB, which is below the Thermal Noise Floor of -15 dB NM, and only 33 kW of 1000 kW ERP are sent in your direction:
Fox also has adjacent channel interference from CHCH on real channel 15.
Ah, yes; I see that chinadog already mentioned that. A very directional antenna can attenuate 15 when aimed at Fox, but maybe not enough.
CHCH is 53 dB stronger than Fox. The max allowed for adjacent interference is 33 dB. But if you already have been able to receive Fox, the tvfool simulation is wrong.
165 - 129 = 36 degrees
The DB8e has a null at about 20 degrees, and a secondary lobe at 36 degrees. The 91XG is a little better, with 10 to 15 dB down at 36 degrees.
That would require a 20 dB antenna null for CHCH or the Two Antenna Trick, or a custom Tin Lee filter.
CITS -69.6 dBm + 15 dB ant gain = -54.6 dBm = -5.8 dBmV
max input of 7777 = 15 dBmV; OK
-54.6 dBm + 24 dB amp gain = -30.6 dBm
-30.6 dBm + 11.5 dB 3412 gain = -19.1 dBm; not quite enough for tuner overload unless you have another source of strong local signals.
I feared adding a regular splitter would leave me with 20dB-3.5dB = 16.5dB or a very margin signal
Did you actually try that?
I just read your original post, so I had to correct my math.
Splitters, Attenuators, Filters, Diplexers, Other Signal Gear