SWR: Cobra 29 and Wilson 5000?

[Choirboy]

I picked up a fairly new (2-3 years old) Cobra 29 NW ST WX that I found on Craigslist today. I figure it, along with my Wilson 5000 Mag Mount, should be a pretty good around town rig for about a $160 investment.

Question is, using the SWR meter in the radio, I'm getting 1.4:1 on channels 1 and 40 and 1.3:1 on channel 19. Is this about what is to be expected, or is there room for improvement? The antenna whip is bottomed out in it's mount.

Thanks!

[521 Houston]

FIRST- try raising the stinger in the holder and see if the SWR goes down or up.

If they go down, continue to raise the stinger until you get the lowest reading. If needed, you can get a longer stinger or longer holder to go on top of the base.

If they go up, try trimming about 3/4 inch off the bottom of the stinger and check them again. The Wilson should get a 1.1 across the band if adequate ground plane is available. Just do NOT cut it above the set screw, so if the SWR does go up when you bottom the antenna after cutting, you'll still have enough length to put it back where it was before you started.

[Choirboy]

I tried raising the whip and the SWRs went up a bit. So, I cut 1/2" off the bottom (I knew I'd eventually find a use for that Dremel Moto-Tool that my Dad gave me for Christmas 10 years ago!) and didn't seem to get any improvement - still around 1.4:1 on channels 1 and 40 . Do I need to cut more? I don't want to ruin the thing....

Thanks!

[Choirboy]

ADDENDUM TO ABOVE....

The antenna is mounted in the center of the roof of my Nissan Maxima, with the coax running down the back window and under the front of the trunk lid. It was shipped with a thin plastic film stuck on the bottom of the magnet. Do I need to peel that off (looks like the magnet would scratch the hell out of the paint if I do....)?

Thanks!

[BigBopper]

No leave that film there, its to protect the paint

[Choirboy]

Well, I played with it some more and got the SWRs down to 1.3:1 on channels 1 and 40 and a bit lower on 19. At this point am I picking nits or will further improvement actually make a difference?

Thanks, y'all!

[BigBopper]

are you using the meter in the 29??? If so they aren't that exact, pick up an external SWR meter, and you'll probably see a difference, 1.4 swr isn't that bad, but not as good as it can be, don't run an amp with that SWR, but it won't hurt the radio

[521 Houston]

Well, I played with it some more and got the SWRs down to 1.3:1 on channels 1 and 40 and a bit lower on 19. At this point am I picking nits or will further improvement actually make a difference?

Thanks, y'all!

Just for giggles, try moving the antenna around a bit. Move it farther towards the rear of the roof, and even try it on a couple of spots on the trunk and see what kind of swr's you get there. Sometimes antennas just want to be in their own little sweet spot, and just refuse to act right until you get them there. Believe me, as much crap as I went through with my Crown Vic getting an antenna to act right, I know this from experience! LOL!

[MudDuck]

try to get the lowest swr's possible, then if needed add a 3' or 6' jumper to the antenna coax connecting either of the two with a barrel connector... Always seemd to work for me.... This should bring it down some also.... Have a great one!!!

[Choirboy]

My understanding from all the stuff I've read is that, if the SWR is identical on channels 1 and 40 and less in the middle of the band, the antenna length is optimized, and further reduction in SWR has to be looked for elsewhere. Is this correct?

Thanks!