High SWR on all Channels using Roof Mount Antenna

[SegWorm]

Just installed a Wilson 1000 roof mount antenna on my SUV. The antenna is mounted through a hole in the center of the roof. It is paired with a Uniden PC68LTX CB radio.

After installing the antenna, I attempted to tune it, but found that the SWR is above 3 on all channels no matter how I adjust it. (I am using an external SWR meter.)

I ohmed the jumper coax and the coax cable leading to the antenna, they both have continuity. The antenna mount has .5 ohms of resistance to ground, which shouldn’t be an issue from my understanding.

Where should I go next? The cables appear to be good, along with the ground. I’m pretty sure the SWR meter is good since I used it for a GMRS radio and it had good SWR.

 

[prcguy]

I would use an antenna analyzer to test out of band to see if its got a good match anywhere. Using an SWR meter either internal or external will only tell you what's happening between ch 1 and 40 but the antenna may be way too long or short and working ok somewhere else. Or maybe nowhere and that can point you to bad connector install or something else that is not related to whip length. An ohmeter reading from connector center pin to shield and center pin of connector to mount center is a basic test that can rule out gross problems.

On NMO and other commercial mounts I have adapters from the mount directly to an N female connector where I can put a 50 ohm load at the antenna mount and check the coax and mount separate from the antenna. Not sure if an adapter is available for a Wilson mount.

 

[ArloG]

Long shot but worth a try. Try several closely spaced loops of coax taped or zip tied where it enters the vehicle.

 

[tvengr]

If the antenna whip has a set screw, loosen the screw and pull the whip out as far as you can and tighten the screw. If the SWR goes up, the whip is too long. If SWR goes down, the whip is too short. Loosen the screw and set the whip down as far as it will go and tighten the screw. What is your SWR?

 

[FKimble]

CB and GMRS are a long way APART! does your meter cover both bands?

Frank

 

[robertwbob]

if whip is too long ,cut a piece of wire same lenght as whip.use the wire to trim n try.when you hit the magic numbers then trim whip tad long n fine trim to perfection. you cant put back too much cu off. why i use wire first

 

[K5MPH]

Like FXimble said make sure the swr meter is really for CB radio and not GMRS or if not the swr meter check for a short ........