Very high SWR unless I unscrew my coax slightly

[Farmradio]

I need help, I’ve search and search and can’t find any advice. Im new to all things CB so im trying to figure this all out as I go. I’m running a Stryker SR-447HPC2 with a 102” whip on a mobile setup. I can’t seem to get an SWR below 8 unless I unscrew the coax on the antenna side until the connector is loose. I’ve tested the coax with a multimeter, replaced the S239 stud and tested it with a multi meter, and I’ve tested ground continuity from battery and frame to radio, antenna mount, and even frame to coax and everything is checking out good. My only thought is maybe I need to replace the mount because the mount is a piece of 1/4” steel plate with a hole drilled through it. Thank you for any help and advice!

 

[chief21]

What type of mount are you using? Can you post a picture?

 

[Farmradio]

It won’t let me upload the picture. It’s a 1/4” plate welded to a flatbed headache rack with a hole drilled through, the hole it big enough that the threads are not touching.

 

[John_S]

Make sure the center conductor is not shorting to ground. You need the set up like on a mirror mount bracket. And when using the 102" whip, you also need the ball mount and spring, as they actually become part of the antenna system. Otherwise the whip will measure short.

 

[mmckenna]

That really does sound like something is resulting in the center conductor touching ground. Unscrewing the connector is breaking that connection.

Those 3/8x24 mounts should have a nylon insulating washer to prevent that from happening.

 

[Blackswan73]

Check the coax from the radio end with a multimeter while connected to the antenna. There should be no resistance reading between the center pin of your connector and the outside of the connector with the coax connected to your antenna. Is your stud antenna base the type which has a female connector on the bottom or just a screw hole and a ring connector? If it is the latter, solder the ring connector to the center conductor of your cable. Just crimping the connector can cause a high resistance or intermittent condition. Also the ring style stud is susceptible to water ingress and will cause damage to the cable.

B.S.

 

[John_S]

Don't always depend on a zero resistance reading at the radio end of coax unless the antenna is disconnected from the coax. Some antennas will show as a short.

 

[Blackswan73]

True, but not a single whip antenna. The condition the OP was describing is very indicative of a short.

B.S.

 

[spongella]

I second those comments, sure sounds like a short to me. Not sure what kind of SWR meter is being used though...one that's built into the radio or an external one?

 

[spongella]

It won’t let me upload the picture. It’s a 1/4” plate welded to a flatbed headache rack with a hole drilled through, the hole it big enough that the threads are not touching.

Is it commercially made or is it DIY? You might want to check on how to properly wire a whip antenna. Center connector goes to the whip, shield goes to ground.