Use the 1x16 amplified splitter with two 1x2 passive splitters and a low pass filter.
Splitter 1 used as a 1x2 (S1 In, S2 Out, S3 Out)
Splitter 2 used as a 2x1 (S4 In, S5 In, S6 Out)
Incoming CATV ---> S1
S2 ------> Cable Modem
S3 ------> Low Pass Filter -------> S4
Modulator ----> S5
S6 ------> 1x16 amplified splitter
Splitter 1 used as a 1x2 (S1 In, S2 Out, S3 Out)
Splitter 2 used as a 2x1 (S4 In, S5 In, S6 Out)
Incoming CATV ---> S1
S2 ------> Cable Modem
S3 ------> Low Pass Filter -------> S4
Modulator ----> S5
S6 ------> 1x16 amplified splitter