Having problem with new antenna or maybe something else.

Very bad reception and sometimes completely dead.

Should the antenna whip be isolated from the body of the antenna? I have continuity when I check it. Also the center pin has no continuity with anything.

This happens with antenna Uninstalled.  I have also checked the coax has continuity pin to pin , shield is intact and continuity all the way through and no continuity between shield and center pin.

Its a 1/2wave so it has a matching network in the base that will read shorted with a multimeter. Much easier to test if you had an antenna analyzer or VNA.

Ok, still seems it wouldn't show a dead short though. I would think it would show some resistance but I guess not.  So where does the center pin go to?

I tried looking up a schematic but couldn't find anything.

If there is a capacitor inline with and right after the feeder center pin, that would look like a DC open circuit to a multimeter.

It would show a dead short if there was an shunt coil inside. Which there isn't; I just pulled the SBB5 off my truck and checked it with a multimeter and it doesn't show a dc short between the pin and the mount.

Right. Pin doesn't have continuity with anything.  Just shows open.

The whip has continuity with the base (mount) ,so it appears to just be grounded.

There is some sort of non conductive spacer between the upper where the whip is attached and lower part of the base. I thought that's where the whip would be isolated from the base.

Just checked both, my old and brand new (never used) SBB5 antennas. Center pin to bracket (shield) shows open. The antenna whip to shield (bracket threads) shows several ohms (Fluke meter isn't very accurate at low resistance). Center pin to antenna whip shows open (infinite).
It's a half wave antenna. There should be a matching section in the base. I don't know what matching design they use.
The old antenna seems to work ok. I haven't installed the new one yet. It's not the best antenna but I like the fact that it requires no ground plane.

ok. Thanks. just wanted to verify . DX engineering sent me a new antenna based on my findings. Both have the same findings like yours. Guess i'll send it back.

When I installed the coax it did get a kink while pulling it through the boot on the firewall. I cut that factory connector and about 2" off the cable and installed a new PL259. no change in signal. I suspect the coax is damaged elsewhere but nothing I did.

My thru thru the glass tram works better. I was hoping for the opposite.

I'll buy a new coax from DXengineering or try to source it locally.