Here's another way this scheme can work, but you have to have heard of the hardware to come up with it -- the UVSJ. It is a Uhf Vhf Separator-Joiner. You feed UHF in one port, VHF in the other, and get a combined signal out of the common port. Or UHF and VHF combined, as off of an antenna, into the common port, and separate bands out of the U and V ports.

Here's today's setup --
I have a client who has a DSS receiver in the room above the cable closet. He wants to send the DSS output throughout the house and thinks that running a piece of cable to the closet will be a truly irritating experience.

Okay, so we modulate the output of the DSS onto a cable channel. Now what? I ask a ridiculous question: what does he actually watch in the room with the DSS receiver? Answer: DSS and channel 9 (he works there). He does not care about cable channels above 13. Enter the UVSJ.

The UVSJ hails from antenna days, and is guaranteed to separate UHF from VHF. Since cable 14 - 22 is in the VHF band, that will go through; what is not specified is what will happen to signals from 23 on up. Presumably they will pass through up to some point, then get snowier and snowier....

Okay, so we get out two UVSJs. At the cable closet, we connect the cable to a "V" port, and connect the common port of the UVSJ to the existing cable. This sends channels 2 - 22 and 23 to ?? up to the TV. At the TV, we connect that cable to the common port of a UVSJ. Why another UVSJ? You'll see in a moment.

We modulate the DSS signal. Upstairs, the output of the modulator goes onto the "U" port, which puts it onto the cable going down (or coming up, if you wish) to (from) the cable closet. In the cable closet, we take the modulated channel off that cable at the "U" port of the UVSJ, then use a standard 2-way splitter, backwards, to mix the modulated signal with the cable feed before the cable feed is split and sent to the rest of the house.

Again, one signal goes one way and the other the other. We have always head that these simple passives are bidirectional. This stuff proves it.