I have a problem.

My husband has installed a Cobra 29LX CB in his Jeep Wrangler. He had a 3' firestick mounted on the back tailgate, but it wasn't getting the best reception so he got a 5' firestick. He's getting less reception (by ear he's assuming when passing traffic) than he did with the shorter one. We've tried doing the SWR testing. Readings are as follows with BOTH antenna on :
CH1: 2.3
CH20: 2.3
CH40: .3
Why is it giving such a low signal on the 40 channel, I know it says that means more height, but he had thought he had better coverage with the 3ft. Could it be a bad ground?? Bad coax cable??? I've searched forums all night, trying to figure out why his "antenna warning" signal keeps going as well. I found that forum where it says to adjust the VR6 (so many digits I've had in my head, I think that's the right knob).. And I don't know who else to ask, before it gets smashed into a million pieces.

 

Thank you all. Antenna wasn't properly grounded. He actually found a CB shop, a gentleman ran testing with external SWR, got a little boosting and he's good to go. Thank you all for your replies, sorry for wasting your time.