The UVSJ is the model number of Pico Macom's UHF/VHF splitter/joiner that is a diplexor with a frequency split between the UHF and VHF bands.
The HLSJ is the model number for their high-VHF / low-VHF splitter/joiner that is a diplexor with a frequency split between the lower (2-6) and upper (7-13) VHF channels.
Holland Electronics and Blonder Tongue use a similar part naming scheme for their equivalent diplexor products. A search for either UVSJ or HLSJ should turn up the correct information pages.
Since these are very common in TV applications, they are not that hard to find and are relatively inexpensive.
The UVSJ is available from Solid Signal for $1.79 + S&H:
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They have the HLSJ for $3.99 + S&H:
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Compared to a JoinTenna (~$20-40) or a custom built diplexor (~$50-120?), these are much cheaper and can be delivered sooner.