antenna ham dipole

So yeah I’ve been a ham for about ten years but have just recently been getting into SDR stuff… I mainly need a good quality SDR radio for HF stuff, 3mhz-54mhz. I wouldn’t mind to monitor vhf/uhf stuff too.. So should I get a RTL Dongle V4 with a dipole kit to start out? Or should I just get one...

I was asked this by a friend of mine looking into ham radio. I was just wondering if that I could run a couple antennas of one 75 ohm coax line? I have a feeling that its not possible but I and the other guy were just curious.