Let me explain the Winegard Sensar v/s the Jack graphically and otherwise
First as someone up-thread pointed out the Jack is a UHF antenna with limited VHF capability the Winegard is a VHF/VHF/UHF antenna (yes there are two VHF bands winegard gets 'em both Jack does too but one of em you almost need to be in the transmitter site driveway)
Second.. We will start with an OMNI antenna
Take a neckalce chain a map and a pin. put the pin in the map (representing yoru RV) and arrange the necklace chain around it so it's in the center.. This is an OMNI.. Now pull it into an egg shape with the RV at the intersection of the Minor and maor axis (THe major is the center of the egg shape divided long wise the minor is the diamater of the "large" part of the egg This is the Winegard Sensar II or III..
Now pull it even tigher (Taller, skinnier egg) This is the IV on UHF (VHF performance not changed)
now add a Sensor pro.. Add a 2nd necklace to the first so they become one longer chain. Same shape.
This is not accurate.. but is is descriptive.