I didn’t notice properly, my bad.
I’d say the new antenna is worse because it’s picking up interference from your TV or another device.
Could you relocate the whole setup away from there and put the antenna in a window or even better the attic?
The connector on that coax isn’t good but shouldn’t be that bad 
Could also be that the adapter you got is just really bad quality … impossible to say.
(but the interference stuff can be mostly excluded by changing location)
You might be better off improving the whip antenna and thus avoiding any adapters.
If you’re adventurous you could try this: Mag Mount Antenna's Whip Replaced By V-Stub Wire Collinear
Otherwise just the normal can under the mag base and cut the whip as described here:
How to improve performance of whip antenna of DVB-T