NMI mount to NmO connector SWR 10+

[Imatensor]

I've got an NMO mount with an NMO antenna connector. The coax is preexisting and hard to route in this bus. I had to solder the connector to the coax copper center conductor. The coax cable is 12' or less but completely hidden coming into the dash bay.

The mount is grounding to the aluminum rail. The connector coax shield is grounding to the mount. Is the my issue?

Should the mount be isolated from the coax shield,,?


I'm Running a President Bill II FCC.

Using the Astatic PDC1 swr.

 

[n3obl]

I see the base of the antenna is the NMO to a stud adapter but what is the antenna? Looks just a spring and a 4 foot whip which if the case will not work for CB without some matching coil?

Might be better off to get rid of the adapter and just use a Larsen NMO27 antenna with or without a spring.

 

[mmckenna]

From what you are describing, your mount is good. The coax shield should show continuity to the NMO mount outer ring.

Install the NMO to 3/8" x 24 adapter and check for continuity:
1. Check the center of the coaxial connector at the dashboard end to the 3/8" x 24 center stud. There should be continuity. If there isn't, something isn't installed correctly.

2. With the NMO to 3/8" x 24 installed and WITHOUT THE whip/spring installed, check for continuity between the center pin on the coaxial connector to the outer shield. There should NOT be continuity.

That'll tell you if your coax, coax connector and the NMO - 3/8" x 24 adapter are good.

I'd agree, that looks like some random length whip and spring that may not be resonate near the CB frequencies. Looks far too short to me, but maybe I'm missing something.

 

[Imatensor]

Correct. The coil is a Signal Kicker off a magnet Mobil mount. I didn't realize it was needed to make the spring whip work correctly. I'll look at the Larsen you mentioned. Thanks!

 

[Imatensor]

From what you are describing, your mount is good. The coax shield should show continuity to the NMO mount outer ring.

Install the NMO to 3/8" x 24 adapter and check for continuity:
1. Check the center of the coaxial connector at the dashboard end to the 3/8" x 24 center stud. There should be continuity. If there isn't, something isn't installed correctly.

2. With the NMO to 3/8" x 24 installed and WITHOUT THE whip/spring installed, check for continuity between the center pin on the coaxial connector to the outer shield. There should NOT be continuity.

That'll tell you if your coax, coax connector and the NMO - 3/8" x 24 adapter are good.

I'd agree, that looks like some random length whip and spring that may not be resonate near the CB frequencies. Looks far too short to me, but maybe I'm missing something.

Ok. Thanks. The antenna was from a mobile magnet Signal Kicker. I didn't realize it wouldn't work without the coil. The coil won't attach to the NMO base. I need an aenna which will but not too long since I'm at '11 ta mount already

 

[mmckenna]

Ok. Thanks. The antenna was from a mobile magnet Signal Kicker. I didn't realize it wouldn't work without the coil. The coil won't attach to the NMO base. I need an aenna which will but not too long since I'm at '11 ta mount already

The NMO-27 that N3OBL recommended would be a good option. It's about 4 feet long and a very flexible whip.
You may have some challenges getting it to show low SWR with the mount hovering over the roof top like that. They are designed for a direct roof top mount where the base is sitting on top of the ground plane.
But it'll probably do well enough.

 

[Imatensor]

I saw some one bend the antenna over and trap the tip in a plastic keyhole. Maybe that is a solution to the length.