What am i missing?

[hayseed]

Back into CB after a few years without. Bought a new Sirio 5000, Mag mount on the roof of a '18 GMC P/U. Can't get the SWR below 2

Tried the old Wilson 5K on the same Mag mount, same thing, TOO high.

Any ideas???

Can't drill it, company work truck.

 

[Magard]

You sure your meter is right.

 

[Handy Andy]

If you're using the same Mag mount for both antennas - seems then the Mag Mount may be the one in error.

Do you have something else, piece of Damp String, Coat Hanger - Old Refrigerator magnets - you can try?

 

[BJ radionut]

If this is a USED Magnet base (OLD) I would say it's most likely dirty connections inside the base (possibly bad ground transfer) and/or a connector issue (PL259).
GL
All the Best
Gary

 

[Handy Andy]

​

If this is a NEW Sirio MAG mount, it's defective - return it or throw it out...they use SO-239 as a "socketed" screw on ferrule base - the "Female side" of the PL-259 on the other end.

To see it (SWR) ABOVE or even at 2 - tells me the Coax in the harness is bad, or the radio is too finicky for the location the mount is being put in - Roof, well, that is an ideal spot. So... then that rules out location - except for bad coax or something at the mount itself.

Without ruining your warranty - better get an RMA and look further into another replacement - even the magnet that holds the base down to the metal where it's mounted - unless you can "break the foil seal" it uses to protect the finish of the vehicle to remove it to investigate, it is best to try a different one; than to get stiffed by costs of repack and refurb if they won't let you off the hook for a bad one to exchange for another in the first place.

 

[bob85]

Have you had the sirio mag apart ?

They must be assembled the right way with the earth tab in the right screw hole or you don't have a ground & its using the coax outer braid.

sirio 5000 & wilson 5k work well on the pl145 mount if its stuck on a reasonable sized metal roof.

 

[Tokin]

Mag mounts are notorious for being poorly constructed and generally have crappy grounds that tend to fail over time especially if they are used in very wet/salty areas.
I have to concur, it sounds like the problem is with your mag mount/coax. Whether its a bad ground or the coax was kinked or pinched maybe. Id try a new mount and test again.
Ive heard of folks having good results with the Tram mag mounts after modifying the ground a little.

 

[Marconi]

Any ideas???

Hey Hayseed.

If you look at the image and you see the roof connection at the window frame on both sides, it looks like it is possible this area may NOT be physically connected, due using some very strong adhesive, sealant, or insulation adhesive holding the roof in place. I figure that making these new vehicles run quieter...is a big thing these days. Who knows, if this roof is spot welded, compression fitted, or not? Maybe you have little to no metal to metal connection from the body to the roof and thus little to no ground. Check it out.

Try behind the light fixture area in the cab, and see if you can check for continuity to the underside of the roof and some other point in the cab or door jam that tests good continuity.

See the dark line that runs along the drivers side of the roof and the window frames from front to back and is close to what looks like another antenna mount.

..........................................................................

 

[M0GVZ]

Those Sirio magmounts have a long lived manufacturing fault. There is no strain relief on the coax inside the mount and nothing to stop it rotating and it is common for the braid to come detached from the brass tag on the inside of it due to the users either tugging on the coax to remove the magmount from the roof or just rotating the coax.

You can check it yourself quite easily. Undo the four screws and lift up the centre. Turn it over and you'll see the brass tab and the braid. If its become detached resolder it back on and also get a hot glue gun and put a dab of glue over the coax where it comes out of the rubber sleeve on the inside of the top section to prevent it being tugged or twisted in the future.