| Author |
Message |
    
Xlaxx
| | Posted on Wednesday, March 19, 2003 - 12:35 pm: | 
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My mobile SWR was a 1:2 to 1 using a Vectronics analyzer. I have a Mag mount Wilson 5000 with a thin, very thin, moleskin material on the bottom to prevent paint scratches on the roof. The ohms were super high,...400 Ohms!
I have a choke coming out of the radio and a choke made from the extra antenna coax, wrapped around a PVC pipe. What should I do??? Should I ground everything? The radio is only grounded with the power cable only.
Thanks
XLAXX |
bruce
| | Posted on Wednesday, March 19, 2003 - 1:02 pm: |
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My magmounts at best were a last ditch efford to get on i can. beleve your readings ..... i dont use them.... magmount= is all else fails. You could run a thin wire to the car frame from the base of the antenna to provide a real ground |
Bigbob
| | Posted on Wednesday, March 19, 2003 - 9:33 pm: |
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Wilson mag mounts come with a weather cap,for when you take off the coil to protect the coax terminal from water,most people lose them,then they take the coil off before the carwash,one ruined mag mount all it takes is once.Water will corrode the braid,even with heavy corrosion an ohm meter will show 0 ohms,but an analyser will show the actual impedance because rf travels on the surface of the braid where the corrosion is.The other problem is you need a sufficient ground-plane,judging by your low swr you probably have,was your setting for high impedance or low on your analyser,if high reset for low then see what swr reading you have. |
Xlaxx
| | Posted on Wednesday, March 19, 2003 - 10:00 pm: |
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Thanks Bigbob and Bruce-
I have one of those screw-on ground planes that goes under the coil. There is a very small gap between the coil and the mount though. My truck has a fiberglass cap on the back. Nothing is really grounded either. I got the magmount b/c I didn't want to drill!
XLAXX |
Tech671
| | Posted on Monday, March 24, 2003 - 5:27 am: |
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Remove the gpk, the choke, and the film. Use analyzer to find what freq it is at 50 ohms. |
de
| | Posted on Monday, March 24, 2003 - 6:07 pm: |
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Re Techie
I am getting this bad feeling that the place where the mag mount is being placed does not have or just has a very bad chassis ground.
XX try this. Run a grounding wire from somewhere on the metal body part you are putting the antenna to the chassis to make certain you are getting a good chassis ground.
A good way to tell if you need to do this is to simply put the antenna on another persons vehicle, one that uses a mag mount and gets a good swr. If it works on the other persons vehicle you know then that the problem lies in your vehicle rather than the antenna.
DE
PS
Lose the moleskin. No matter what you do you ar going to scratch up your vehicle some way some how. It is just a matter of time. To minimize the area of scratches just put the antenna in the same place all the time. |
Znut
| | Posted on Monday, March 24, 2003 - 10:24 pm: |
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Xlaxx,
NOT a good connection somewhere, or your coax chokes aren't working well with your system.
If you leave extra material between the mag mount and the chassis it may blow off. That may break your coax and compound your problem.
Is your Wilson used? (i.e. before you aquired it?) It may have been shorted or in some other way blasted so that the matching network is blown or broken.
In short, a quality antenna system should tune up easy without too many mods in the feedline and mount.
Also, check your coax. Could be a broken or intermittent shield.
Znut |
Xlaxx
| | Posted on Wednesday, March 26, 2003 - 8:49 pm: |
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I took the moleskin off the bottom of the magmount for the Wilson 5000 and put a 6ft jumper between the foot warmer and meter. Got the SWR's down to 1:1 on Ch 1 and 1:2ish on Ch 40,... WITH THE FOOT WARMER ON!!!!
Still need to check the ohms though, I borrowed the Vectronics meter so I have to check it later.
Again, getting great R's. I think, I'm going to take the big choke out (between the radio and warmer) and slip in a 6ft jumper instead then just go with it. The excess coax from the antenna is coiled around a piece of PVC pipe.
XLAXX |
Xlaxx
| | Posted on Friday, March 28, 2003 - 11:45 am: |
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Took the big coiled choke out that was between the radio and amp and lost swing on the radio's meter. I did get more power output, at least the Syncron meter says so. Using a brand new Aries Belden 6ft coax jumper.
The meter on the radio use to slam to the right and swing back and forth while talking but now it just barely gets into the red. Using an Astatic Black D104 handheld mic cracked open. R's are still really good 1:1 on Ch1 1:2 ish on 40 with amp on.
Where did my swing go?
XLAXX |
Xlaxx
| | Posted on Friday, March 28, 2003 - 2:52 pm: |
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Coiled Choke in-line = Swing on radio's meter into the red with about 5-10 Watt decrease on final output.
6 ft Coax in-line = No swing on radio's meter yet increase in output wattage by 10-15 Watts.
SWR's are about the same with either in line.
Sacrifice swing or wattage?????
Any other suggestions???
Thanks
XLAXX |
Kiwikid
| | Posted on Friday, March 28, 2003 - 4:49 pm: |
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Hello Team,Xlaxx to prevent severe scratching you could try putting a thick layer of wax on the area you intend placing the antenna.
regards Kiwi Kid |
Xlaxx
| | Posted on Saturday, March 29, 2003 - 9:25 pm: |
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Kiwikid
Thanks for the tip!
XLAXX |
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