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Message |
    
Kwhubby
Junior Member
Username: Kwhubby
Post Number: 10
Registered: 12-2004
| | Posted on Saturday, May 14, 2005 - 2:35 pm: | 
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Hi, I am helping a friend set up a wilson silver load antenna on the back of his pickup truck (well the side of it) and something seems off. We got rg 58 coax connected from the radio to the antenna mount but when I do a test for swr im getting like 7:1 swr or higher (4 watts). I was scared to leave the key on afriad of killing my poor cobra 148 gtl. I would try adjusting the tune screw or disconnecting the funny ground wire, but with this super high swr I am wondering if the mount adapter to screw the antenna into is wrong, as I can't find any information about it anywhere else. The adapter came from a radio shack mount that the guys there said it would work, and the antenna screws in fine. On the wilson silver load the plug is all one contact but in the middle on the bottom there is a little hole as if it is for the power lead, like as if it was a tv coax adapter. On the mount adapter there is no center plug spike thing just a flat surface in it (maby two contacts the bottom and side tho can't really tell). Should I return the adapter and get something else (I would need to know the correct adapter) or should I try to tune the antenna?
Thanks |
Red_devil
Member
Username: Red_devil
Post Number: 95
Registered: 10-2004
| | Posted on Saturday, May 14, 2005 - 9:40 pm: |
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Kwhubby,
First, I have NEVER had to use the matching lead on the Silver Load Antenna. I bet you will find a short somewhere in the mount or coax with a SWR that high. You’ll need a multimeter for this, but here goes. Make sure that the center lead of your coax has continuity with only the metal base of the Silver Load Antenna and NOT a ground. Then double check that the outer, shield, of the coax HAS continuity with ground. If both of these check out with the matching lead disconnected then you may have other more serious issues. Try the continuity check first. Let us know how it goes.
I have included a photo that shows a Wilson Silver Load with the matching lead tied off using a zip strip on a mirror mount for reference. Without the matching lead this antenna had no problem with the standard CB band at 1.1:1 to 1.3:1.
CEF447
Red Devil – 392
KE5EUN
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Bigbob
Senior Member
Username: Bigbob
Post Number: 1898
Registered: 12-2001
| | Posted on Sunday, May 15, 2005 - 7:09 am: |
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And don't forget the nylon washer goes on top of the mount between antenna base and bracket,you won't believe how many people install it wrong or say"whats this extra part for?".Bigbob |
Kwhubby
Junior Member
Username: Kwhubby
Post Number: 11
Registered: 12-2004
| | Posted on Monday, May 16, 2005 - 4:09 pm: |
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Ah thank you, I will try this. You have one of those silverloads so could you disconnect it and show me a picture of the inside of the mount? Or if you could just tell me if there is a center pin type of thing going into the hole on the bottom of the antenna. I may also take a detailed picture of the setup with the mount and the antenna demonstrating my concern. This is not a wilson mount its a thing from radio shack and just the adapter taken out of the mount and screwed in a spot on the truck frame. About that washer, what is this for- to isolate the adapter from the metal frame so its not grounded?
Thanks so much for all your help. |
Red_devil
Member
Username: Red_devil
Post Number: 95
Registered: 10-2004
| | Posted on Tuesday, May 17, 2005 - 8:18 am: |
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kwhubby,
Under normal circumstances I would be more than happy to upload another photo. However, I am out of town until Saturday. (Ain't computers great?) If you want to drop me an e-mail hit my profile and I will send you some photos when I get home.
But, this may help in the meantime. Again there should be no continuity (connection) between the antenna element and the mount. The mount in the picture has an isolated inner core that only makes contact with the antenna itself. The nylon washers (top and bottom) that Bigbob mentioned are essential to maintaining that isolation. The outer part (shield or chassis ground) does make contact with the mount and any other ground on the vehicle. With that in mind, double check all of your connections.
Good Luck!!!
CEF447 |
Kwhubby
Junior Member
Username: Kwhubby
Post Number: 12
Registered: 12-2004
| | Posted on Tuesday, May 17, 2005 - 12:12 pm: |
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Ahh, thanks Red devil that helps clarify things. If I am understanding this right the isolated adapter is connected to the center lead of the coax but not the ground of car, and so there is only one contact to the actual silver load antenna being the hot lead (unless the matching lead is used). but the outside of pl259 male adapter whateve its called is connecting to the ground of the car. I don't think I need any more pictures now because I think I understand exactly how this works. If I have more issues I may take a picture and post it. Thanks again. |
Red_devil
Member
Username: Red_devil
Post Number: 96
Registered: 10-2004
| | Posted on Tuesday, May 17, 2005 - 1:05 pm: |
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Correct!!!! The antenna connects ONLY to the center lead of the coax :-). The coax sheld and the mounting hardware must make contact with the body of the vehicle, which generates the grounding effect of the antenna system.
Enjoy!!!
CEF447 |
Bigbob
Senior Member
Username: Bigbob
Post Number: 1913
Registered: 12-2001
| | Posted on Tuesday, May 17, 2005 - 7:57 pm: |
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Thanks red devil,couldn't have said it better myself,I love it when people really try to help.Bigbob |
Red_devil
Member
Username: Red_devil
Post Number: 97
Registered: 10-2004
| | Posted on Saturday, May 21, 2005 - 7:22 pm: |
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kwhubby,
How is it going with the Silver Load?
Bigbob,
Thanx for the compliment. I get so few that they have become more and more important.
CEF 447 :-) |
Red_devil
Intermediate Member
Username: Red_devil
Post Number: 101
Registered: 10-2004
| | Posted on Friday, May 27, 2005 - 2:41 pm: |
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I guess all is good.
Enjoy!
CEF447 |
Kwhubby
Junior Member
Username: Kwhubby
Post Number: 13
Registered: 12-2004
| | Posted on Wednesday, June 01, 2005 - 8:24 pm: |
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Hi again, actually no its not so good but I did make sure the mount adapter was installed correctly and that connections were ok. I haven't gotten a chance lately to help him again because Ive been preocupied by things. Last time I helped him I thought it was a bad ground due to the fact that there was about 57ohms of resistance from the coax shielding to the frame of the car. The mount piece was being connected to a hole already in the car and the paint was not scratched off underside to get a good contact. Since then he has scratched off the paint and reconnected it but I haven't tested swr since. The hole it is connected to is in one of the 4 about 3" holes on the side of a pickup truck were I guess you can use these to put one of those roof tops on the truck if you wanted to, I believe they are called "stake holes". There is a nice hole in the bottom of it in the steel where the wilson silverload-pl259 adapter fits nicely. If getting a good ground doesn't help I guess Ill probobly end up trying to mount this differently. Another note, the coax run is 20' long rg 58 pl259 ended both sides (from radio shack only crimp connected) although wilson recomends to use 18'. Ill try more things when I get a chance, any suggestions is helpful. |
Red_devil
Intermediate Member
Username: Red_devil
Post Number: 103
Registered: 10-2004
| | Posted on Tuesday, June 07, 2005 - 10:41 pm: |
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Sorry it took so long for me to respond. I guess at this point I would double-check all connections for tightness and appropriate continuity. Again NO CONTINUITY between the center coaxial lead and ground or antenna mount. Get a SWR check and if that does not work, send me some photos or I can send you or post some more that may help clarify any questions. OH, those cheap crimped R-S coax cables may be some of the problem :-)
CEF447
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