SWR Woes with Wilson Trucker 2000 and RV Ladder

[Highlander_821]

So I got the last couple of things to mount a Wilson 2000 Trucker (10 in. shaft) on the ladder for my RV using a 4 bolt bracket mount.
SWR is quite bad. I'm around 3.4:1 at 29 Mhz, even with the whip at its shortest. The SWR actually goes down as I go down in frequency. About the best I get is between 25 and 26 Mhz, and that is right around 2.8:1 Not good at all.

Thoughts? Using 30 feet of RG-8x. My first thought is the ladder is not enough of a counterpoise.

 

[Quiksilver]

I think you would need to bond that ladder (or mount) to the RV. Ladder may be isolated from RV body with bushings or plastic washers. Think you need continuity between ladder and RV body to form some bit of a ground plane effect.

 

[BC Coyote]

Not enough groundplane. You need to bond the ladder to the RV body with some good quality ground straps. You could also cut a couple of wires 8 feet long and just run them out from the grounded base of the antenna across the roof of the RV. Doesn't really matter how you tie them down...whatever works. You are essentially creating a counterpoise groundplane for the antenna. It should bring your SWR way down.

 

[Crawdad]

I second what Mr. Coyote said. A couple wires (at least) 90⁰ to the Wilson feedpoint will give the current a real return path, increase the strength of your pattern and lower the SWR. Should be easy to deploy and remove when it's time to hit the road. The more wires the less need for fooling with grounding ladders and such.

7 3

 

[Highlander_821]

Thanks for the replies, guys. I really appreciate it!
I will first try the counterpoise wire approach. If that doesn't do the trick, then I will attempt to bond the ladder to the RV chassis.

 

[Highlander_821]

Ok, so this morning I added 3 102" wires attached to the antenna mount and spread them out on the roof of the RV and temporarily taped them down.

I am now getting an acceptable SWR, but the low point is down at 25.5! It goes up to around 2:1 at 27, and is well above 3:1 at 28. This is weird, because the whip is all the way retracted on the antenna. No way to shorten it without cutting at this point. I suppose I can do that, but it seems strange to me that the curve is looking like this with a stock 27 mhz antenna at its shortest adjustment point.

Any ideas? I don't want to rush into cutting it if there might be another reason for this.

 

[Crawdad]

The 10" shaft makes the antenna longer thus resonant at a lower frequency. If you have it you might try the standard length shaft. If not, shortening the whip is the next option.

7 3

 

[Highlander_821]

Ok, so any suggestions on how to actually cut the whip? It is just laughing at my side-cutters.

 

[Crawdad]

Right angle grinder with metal cutting wheel. Dremel with same. Hacksaw. That stainless ain't easy to cut.

 

[Crawdad]

Don't quote me but memory says Wilson has a whip cut chart for the different length shafts

 

[doffo]

Cut very small lengths and check your SWR to be sure its getting closer to where you want it to be. Dont want to cut off 1" at a time, but more like 1/4 at time when you are really getting close.

I have a cutting wheel to take off bits off the antenna whip. maybe the initial cut off an inch since you say its at around 25.5 Mhz, then see where it brings you to.

 

[Xracerx13]

wrong shaft, you need the 5" shaft. Don't cut the whip. change to the 5" shaft.

 

[Highlander_821]

wrong shaft, you need the 5" shaft. Don't cut the whip. change to the 5" shaft.

Too late! I have already cut the whip. (Like quite a bit, lol)
I do have a very good SWR curve now, covering all of CB band up to about 28.8 with readings under 2.0 at the ends and flat right at 28.0

Is there any disadvantage to having done it the way I did versus changing to the 5" shaft? I chose the 10 inch shaft to get the antenna as high above the roof of the RV as possible.

Did I screw up?

 

[Crawdad]

Too late! I have already cut the whip. (Like quite a bit, lol)
I do have a very good SWR curve now, covering all of CB band up to about 28.8 with readings under 2.0 at the ends and flat right at 28.0

Is there and disadvantage to having done it the way I did versus changing to the 5" shaft? I chose the 10 inch shaft to get the antenna as high above the roof of the RV as possible.

Did I screw up?

IMO no you didn't. If for some reason you need the whip longer replacements are available from Wilson. Glad you resolved your issues.

7 3

 

[Highlander_821]

IMO no you didn't. If for some reason you need the whip longer replacements are available from Wilson. Glad you resolved your issues.

7 3

Thanks. I hope I didn't mess it up. I actually did all the cutting and measuring swr with the whip all the way retracted inside the antenna. So if I want to increase length, I probably have 4 inches or so to play with. But I have much more interest in having 10 meters available rather than the below channel 1 freeband. That can be sort of fun sometimes, but not at the expense of not having 10 meters. I have a little AT-100ProII tuner if I really want to go down there.