I assume from your description that the cable with the HD signal does not also have a DSS signal on it. right? If so, you are dealing with a garden variety TV signal. Split it with a 2-way splitter. If that causes problems with the two receivers, then you signal level was just barely enough for one, and you will have to amplify it before the splitter. Mast-mounted amps and a splitter that passes DC on one leg (or a DC block on the other leg) should do nicely.
As for not being familiar with UHF, it works very much like the RF part of a DSS signal, except it actually goes further on a cable. If you can distribute DSS signals, you can distribute UHF and VHF. You just need to be sure your splitters cover the right frequency ranges and remember you don't have to deal with polarity or the DC voltage that is present in all DSS cables.


If you are using one cable for UHF and DSS signals, then yes, you will need to use a diplexer or add more cable runs, and split the signal after you separate the UHF from the DSS.

Ernie