High swr on a Wilson 5000

[highland512]

I had some static coming through the other night so I checked my k40 out and the coil was full of water. So I got this off a guy at work and now I'm trying to set the swr.

Antenna is mounted in the middle of the truck behind the cab and the coil is above the cab.

I had no troubles getting a 1.2 swr with the k40 but this Wilson 5000 doesn't seem to want to get much below 2.8

Any advise?

[TheCBDoctor]

I had some static coming through the other night so I checked my k40 out and the coil was full of water. So I got this off a guy at work and now I'm trying to set the swr.

Antenna is mounted in the middle of the truck behind the cab and the coil is above the cab.

I had no troubles getting a 1.2 swr with the k40 but this Wilson 5000 doesn't seem to want to get much below 2.8

Any advise?

Good morning highland512,

It is unusual to have an SWR problem with any Wilson base loaded antenna. If it is mounted at the top of your cab it should have a flat low SWR. Have you tried it on any other location of your vehicle? Try raising and lowering your whip and take a measurement. If the SWR is lower when you drop the whip to the bottom of the load, then try cutting off 1/8th of an inch and see if it drops. If it does, then cut another 1/8th off until it drops to 1.5. You can always cut but can never lengthen it again.

If lowering and dropping the whip makes no difference then the whip length is not the problem. The top of you Cab may just be a bad ground-plane. Usually an SWR between 2.5 to 1 and 3:1 to 1 is an indication of a poor ground plane.

Good luck

[MDYoungblood]

Like usual TheCBDoctor has some great advice. I believe you are talking about a Wilson 5000 center load antenna, the type like is used on a mirror mount. I am thinking that if the antenna is new they are inherently made long so they can be tuned, like TheCBDoctor said tune it the same way. Now if it is a used antenna just the opposite might be the case in which you will have to add a riser (or spring) to adjust what has already been removed. Tell us if it's new or used and if the suggestions worked for you, thanks.

3's

Greg

[highland512]

It is a barely used Wilson 5000 with a 10" riser. I don't think I can move the antenna location, I'm afraid it won't look very good. Coax looks all good and the mount has a good ground.

I'm starting to think the whip is to short.

[MDYoungblood]

Slightly used still could mean it has been cut to adjust the SWR. Is the riser you are talking about the shaft from the mount to the antenna's load? A quick trick if you think the antenna is short is to take a piece of solid copper wire maybe 4 inches long, make a couple wraps at the top of the whip or tape it with a couple inches sticking straight up, check the SWR to see if it changed for the better.

3's

Greg

[highland512]

That is correct. I will try the wire tomorrow

[barefoothank]

I followed their advice with my Little Wil and moved it to the far passenger side as possible and dropped from 2.0 to 1.5.
On a side note for me donation to the forum has more than paid off with the info I get here.
Thanks Guys!
hank

[highland512]

So I just found that the guy I bought this from replaced the Wilson 5" shaft (from the coil load down to the antenna mount) with a 10" shaft. Would this distance have to be cut from the whip?

[MDYoungblood]

If that antenna is the Wilson T5000 they made it with a 5" and 10" shaft, both antennas used a 49" whip. To make up the difference the coils are different, one has more windings then the other. If he changed it out than replace it with the 5" and see what the SWR is like, probably the reason he sold it was he couldn't figure out how to tune it. Most center load antennas tune in less then an inch of moving the whip.
Before changing the shaft try the wire trick again this time go 3",then 2", 1" to see if the SWR changes, if it doesn't then change the shafts and start over again.

3's

Greg

[highland512]

So am I not correct in trimming from the whip would solve the issue? I did not no the coils loads where different from the 5" and 10" shaft.

[MDYoungblood]

What I am saying is theatrically both antennas are equal to quarter wave length, (9ft+/-), both have the same length whip so the difference in total length has to be made up in the coil. Measure the whip (49") to make sure it's not been cut already. If you have the 5" shaft I would reinstall it to see if the corrects the SWR. Personally I would hate to remove 5"s of the whip, that is were most of your signal is.
You are using an external meter when adjusting the SWR and following the rules, vehicle in the clear, doors closed, etc., and taking a reading at 3 channels 1, 19, and 40, also close to the cab below the roof line is never a good location for the antenna.
If anything this is a learning experience about buying used antennas, unless you know all the facts you don't know what your getting. Sometimes they aren't the bargain we think they are.

3's

Greg

[-357Mag]

High SWR's in a Mobile that will not adjust are usually lack of a good ground (Ant / Body) not enough Ground Plane, a Broken Antenna, or a Bad Coax. On a few occasions I have seen the coils fail on the Wilsons and they will not match no matter what you do. Get your VOM and check the coil to see if it has a short: Put on lead above the coil and the other to ground with the meter on the OHM scale. The needle should not move / or the display will remain all Zeros if it is good. I'd check my coax as well center pin to the case across both PL 259 connectors. this simple tests will eliminate allot of the Guess work. I bet the problem is either in the Coax or the Antenna mounting.

[MDYoungblood]

Actually an antenna analyzer would pinpoint the problem immediately but you can't use what you don't have. I make suggestions using what most have to work with.

3's

Greg

[highland512]

Well the price on the antenna was was free so I'm not to hart broken. I think I might try trimming in the whip and see what happens. If it don't work I will save it for another application. Anybody got any reviews on the hustler scb antenna's?

[MDYoungblood]

The Hustler SCB model antennas are fine, easy to adjust but they are shorter then the Wilson, if your not running gobs of power look at the Hustler HQ-27, it's around 55" long and has a good bandwidth for the 10m conversion radios.

3's

Greg

[-357Mag]

Next to a 102 the best antenna I ever used for a mobile I got at Rat Shack Stainless Steel Mobile CB Antenna zillion deg below 0 or death valley neddles Ca hot the SWR was always rock solid and they can take a Beating, for 24 bucs you cant beat it, I worked the world on mine.

(Edited by MDY)

[fivefifty5]

I have this same antenna with the 10" shaft. I got at a discounted price because of missing shaft. Got the 5" had the 10" in my hand when I found the 5". So after not being able to get swr down, I got the 10" and now have almost a perfect match. But, the cheap magnet I have (30.00 from flyinJ) a few months latter while messing with an amp, I found it had twisted in the middle. I would use a fluke to get it back right and it would hold fine, so now today it went from an every now and then problem to a 100% problem. Back the little wilson for now. Having said all that, how bout a better magnet?

Dont mean to hijack this thread to a magnet discussion but would be a better mag mount for this antenna? Mag mount is my only option. I have 2013 f-250 super duty crew cab 4x4 diesel with ladder rack, tool boxes on 3 sides and a very much used bed with green electrical apprentice's crawling around all over it for ladders.

[highland512]

I have this same antenna with the 10" shaft. I got at a discounted price because of missing shaft. Got the 5" had the 10" in my hand when I found the 5". So after not being able to get swr down, I got the 10" and now have almost a perfect match. But, the cheap magnet I have (30.00 from flyinJ) a few months latter while messing with an amp, I found it had twisted in the middle. I would use a fluke to get it back right and it would hold fine, so now today it went from an every now and then problem to a 100% problem. Back the little wilson for now. Having said all that, how bout a better magnet?

Dont mean to hijack this thread to a magnet discussion but would be a better mag mount for this antenna? Mag mount is my only option. I have 2013 f-250 super duty crew cab 4x4 diesel with ladder rack, tool boxes on 3 sides and a very much used bed with green electrical apprentice's crawling around all over it for ladders.

Mount it to the ladder rack. I mounted an antenna on the headache rack of my company f-250 and it works like a champ.

-- Monday, 10 November 2014, 20:42 PM --

Issue finally resolved!! I replaced the coax and put in a new whip and right off the bat the swr is down to 1.8. I did some more moving and trimming and we are not looking at a 1.2-1.3.

Good enough in my book. Thanks for all of the advise.