I notice my combo antennas do NOT have a splitter in joining the two
antennas.

If I add a UHF antenna to my VHF antenna - 4 feet apart, MUST I use a
balum or joiner/splitter 300 to 75 bla bla bla.

What is the result if I just join them with 300 ohm twin lead and
then balum to 75 coax for the run to the TV?