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102 whip on jeep liberty. SWR issues.

M

mustang_gt_350

Member
Jul 26, 2013
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Alright heres the story. I pulled the 102 and the spring off of my trucks ball mount on the fender to try on my jeep. I drilled a hole into the spare tire carrier and got a heavy duty stud. I intstalled the whip. I was having way over 3+ swr's so i cut a set of old cheesy jumper cables down and used both the wires to ground from the base of the stud to the swing gate guide right below the latch. I'm guessing the wire is 8ga and i used 2 of them. So tested SWR again and I'm now getting 2.6 on ch1 and 2.2 on ch40. I so being aggervated i tried another ground. I clipped a jumper cable onto the end of the connector on the ground side of the antenna stud and put the other end on a bolt that holds the class 3 hitch on. It dropped the swr like .1ish. So is this about all the better i'm going to get? i never had this problem on my truck. Infact I'm heading out the door to toss it back on the ball mount and run a swr check on the truck with the same meter and radio just for giggles.


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Man, that is one rusty spring. So long as there no problem with it conducting, that should still be OK. You have it grounded to the 'swing gate'; but are you sure that is well bonded to the frame?

I like to keep mobile antennas above the roof; not along side of or well below it. The only part that is effectively radiating is the portion that is above the roof - anyway. Having the antenna mounted as you have will also skew its radiation pattern considerably - as well. Think you would probably do better with a mag mount antenna (Sirio Performer/5000 and the like) on top where it would have far better radiating character.

Just keep in mind that the best SWR a 1/4 wave steel whip should be is 1.5:1. Most of the vehicles made these days - foreign or domestic - don't electrically bond the doors, hood, trunk, and so on. This will also affect how it tunes.
 
I grounded the wheel mount to the inside of the swing gate latch, on the jeep side not on the door side. So it should be grounded to the body,chassis of the jeep. Minus the doors and hood since i don't have ground straps on them.

I just checked with the same antenna on my truck. 2.1 on ch1 and 1.7 on ch40.
 
So you think i should either mount it on the roof (which will put it too high) Or just go with a shorter base loaded, top loaded, or mid loaded shorter antenna?
 
ground problem

its a ground problem does the spair tire mount have a rubber gasket be hind it if so remove the gasket or run a ground strap from the spair tire mount to the body of your jeep and you should be good
 
959 said:
its a ground problem does the spair tire mount have a rubber gasket be hind it if so remove the gasket or run a ground strap from the spair tire mount to the body of your jeep and you should be good
Click to expand...

I had the spare tire holder off and never saw a rubber insulator. But the contact points are painted. However i have the 2 ground wires running from the base of the stud to the body of the jeep, so that should have the mount grounded.


Edit: I also even took a jumper cable off the base of the stud (the bottom side) and ran clipped it to the bolt holding the hitch and that never really changed anything
 
mustang_gt_350 said:
So you think i should either mount it on the roof (which will put it too high) Or just go with a shorter base loaded, top loaded, or mid loaded shorter antenna?
Click to expand...

350, in my opinion the spring should have a braided strap inside and from top to bottom that carries the current. If it is not in good shape or is also rusty, then you are likely to see problems. Try the antenna without the spring. It won't be right in the middle of the CB band, but it should be close enough for government work.

If you don't have a suitable and effective ground system for a 1/4 wave whip, you will likely see higher SWR along with higher than necessary ground losses.

I ran 1/4 wave whips connected directly to the bumpers of many Chevy truck steel bumpers over the years, and that setup matched up good enough for safety and function. Of course there will be some skewing, but that can be an issue with little troubling consequences.

If you want perfection in your antenna pattern...then build a base setup. Forget that mobiles are inefficient. They can still be effective, and with a whip you will know it is not happy unless it shows a match similar to what Robb suggested about 1.5:1 SWR.

The coil type antennas really don't do well with conductive body mass close to the sides of a shortened coil type antenna. The big deal with a 1/4 wave whip is...they need a good ground plane in order to work best. Coil types deal a bit better with a poor ground, but they also require they be well in the clear of the conductive mobile body.

IMO, the whip by itself (no spring) could work better with a stud mount on the outer edge or side of your all steel real bumper. Of course the bumper needs a good welded connection to the body, and not thru a shock like device used in many modern vehicles.
 
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mustang_gt_350 said:
So you think i should either mount it on the roof (which will put it too high) Or just go with a shorter base loaded, top loaded, or mid loaded shorter antenna?
Click to expand...

Yep.

A Sirio Performer is the tallest of the base loads. It will probably create clearance problems; but at least it will be in the center of the roof and radiate relatively equal. The tip of the Sirio will be higher off the ground than your 1/4 wave steel whip is now.

Don't give up on your antenna yet. Sort through the suggestions made and follow through if you can. If that doesn't pan out and you cannot make it work, then consider going with the base loaded Sirio - IMO . . .
 
Last edited:
Marconi said:
350, in my opinion the spring should have a braided strap inside and from top to bottom that carries the current. If it is not in good shape or is also rusty, then you are likely to see problems. Try the antenna without the spring. It won't be right in the middle of the CB band, but it should be close enough for government work.

If you don't have a suitable and effective ground system for a 1/4 wave whip, you will likely see higher SWR along with higher than necessary ground losses.

I ran 1/4 wave whips connected directly to the bumpers of many Chevy truck steel bumpers over the years, and that setup matched up good enough for safety and function. Of course there will be some skewing, but that can be an issue with little troubling consequences.

If you want perfection in your antenna pattern...then build a base setup. Forget that mobiles are inefficient. They can still be effective, and with a whip you will know it is not happy unless it shows a match similar to what Robb suggested about 1.5:1 SWR.

The coil type antennas really don't do well with conductive body mass close to the sides of a shortened coil type antenna. The big deal with a 1/4 wave whip is...they need a good ground plane in order to work best. Coil types deal a bit better with a poor ground, but they also require they be well in the clear of the conductive mobile body.

IMO, the whip by itself (no spring) could work better with a stud mount on the outer edge or side of your all steel real bumper. Of course the bumper needs a good welded connection to the body, and not thru a shock like device used in many modern vehicles.
Click to expand...

I have a base at the house, i'm still tweaking the antenna for it, but its right around 1.3-1.5.

I'll get the meter out and see what if i can find between the chassis and the tire carrier.

my bumper is mostly plastic, i don't know if there is any steel under the plastic
 
Just checked with the meter. Set on the 200 ohm scale from the screw part of the coax connecter on the cb side (cb unhooked) to the latch on the drivers side door frame i'm getting a reading of .2
 
I know many CBr's can see RF and electrical currents flowing in the air and on their antennas. That is why we hear so many good references to what is going on in the real world of CB radio.

So, when they tell us that a mobile whip won't work attached to a P/U truck bumper...they are probably talking out......

Unlike many CBr's I don't know exactly how currents flow or how they are effected by their surroundings, because I can't see this stuff. But, here is what Eznec indicates is likely going on with a model of a pick up truck with a 1/4 wave whip mounted on the center top of the cab vs. the same with it mounted on the outer edge of rear bumper.

I have <gotproof> and I have words too.

View attachment P_U truck mounts.pdf

In these examples it is permissible for you to look at the pictures after you read my words for what the models represent. If you have questions, please read the manual...available on line.

This mobile model was provided to me by our member Henry in Holland, I think.
 

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