| Author |
Message |
    
Epson14
Junior Member
Username: Epson14
Post Number: 12
Registered: 3-2006
| | Posted on Thursday, October 26, 2006 - 6:27 am: | 
|
Hi everyone , ive got a swr question . Ive read alot of the threads on swr problems here but cant really find anything to help with what im running into . Here is the deal . Ive got a S-9 that im trying to hook a 102 inch whip to on my truck . All my hardware is new . I have the setup up on a toolbox , which I made sure that I ran a good ground to because the toolbox is sitting on a bedliner with only j hooks holding it down . Now , I have my radio on one of those console/speaker things that you just sit on the hump . So here is the thing , im using a radio shack meter which I trust cause ive used it many times before an its always been ok . I cant seem to get my swrs below 3 . Now , here is the thing that really throws me . I tryed running a ground to the radio an the swrs go even higher when I do that . My coax is about 18 feet . Any ideas ? Thanks for any input , Mike . |
Tech237
Moderator
Username: Tech237
Post Number: 594
Registered: 4-2004
| | Posted on Thursday, October 26, 2006 - 9:45 am: |
|
1) Are you using a spring under the whip? If so the braid inside the spring may have broke thus adding the length of the spring to the antenna.
2)Make sure you plugs on the coax are good, and that you continuity where you should and no shorts where you do not want them.
3) I suspect the SWR when you ground the radio is more accurate and that some of your problem maybe RF on the outside of teh coax's sheild. Try using a choke on the cable as close to the antenna as you can.
4) If it can be done run a couple of screws thru the tool box into the chassis to help with grounding it. It is possible that the strap ground you added is not properly grounded.HOw long was the ground you added at the antenna end?
5) if you can either borrow a dummy load and test the SWR meter or borrow another meter and see if that gives you the same readings.
6) What happens if you plug the meter in right at the base of the antenna using a very short length of coax? The 18ft length MAY be giving a false reading at the radio. To see exactly what the SWR of the antenna is you should use electrical 1/2 waves of coax or multiples of 11ft 6" for 50 ohm cable. I rate this as the least likely cause but it may pay to check.
Hope this helps and any more information you can feedback may help pin the problem down. |
Dx431
Senior Member
Username: Dx431
Post Number: 1204
Registered: 2-2002
| | Posted on Thursday, October 26, 2006 - 12:11 pm: |
|
What type of mount are you using? Ball mount, mirror mount, home brew? |
Hotwire
Senior Member
Username: Hotwire
Post Number: 1939
Registered: 1-2005
| | Posted on Thursday, October 26, 2006 - 1:16 pm: |
|
Try to better ground the toolbox to the truck and there are 2 things you need for the correct installation of a 102 inch whip. You need the 4 inch spring. Bend it over and make sure you have a braid ground strap inside and its not broke. The braid is to keep the spring from changing the swr to much as it bends over and a good connection. The other piece you need is the 2 inch wide ball mount. See the 102 inch whip is 6 inches short of perfect resonance in the cb band. The 4 inch spring plus the 2 inch ball will make the whip 108 inches and perfectly tuned. This is the correct way to do a 102 inch install. Another very important rule is to have the antenna above the vehicle as much as possible. As the feed point goes below the ground plane SWR increases. Add some length to the whip and see what you get! Hope I can help. |
Epson14
Junior Member
Username: Epson14
Post Number: 13
Registered: 3-2006
| | Posted on Thursday, October 26, 2006 - 1:43 pm: |
|
Thanks for the suggestions . The mount im using is a mirror mount . Are the ball mounts better ? Or does it matter ? Thanks again , Mike . |
Dx431
Senior Member
Username: Dx431
Post Number: 1205
Registered: 2-2002
| | Posted on Thursday, October 26, 2006 - 2:20 pm: |
|
Make sure the nylon washer on the mirror mount isn't cracked and installed correctly. If so, replace it. Also, installing extra ground straps
will help. Double check your coax. Make sure you didnt pinch it and the connectors are good. |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 2207
Registered: 9-2004
| | Posted on Thursday, October 26, 2006 - 6:54 pm: |
|
i have found that when everything seems to be right on a 102" whip install and the SWR still goes to 3 or more, that its more than likely a groundplane issue.
i have used a mirror mount to mount a 102" whip before and acheived a 1.3 to 1 SWR so i know it works.
yes, you should attach a ground wire from the radio's chassis (not the black wire!) to the vehicle's chassis, if possible, do it on both sides of the radio. use the mounting bolts for a convenient place to run the wire to.
how is the mirror mount attached to the truck box?
did you just use the front angled part and bolt it to the side of the box?
thats how i did mine. try to keep it as far from the cab as possible.
use more than just one wire to ground the truck box to the bed. use braided straps or battery cables, and run one on either side of the box to the bed.
now run a wire from the bed to the cab on both sides of the truck.
un hook the coax from the antenna mount.
using an ohm meter, make sure there is not a dead short in the coax by touching one lead to the center conductor and the other to the shield.
there should be no continuity.
unplug the coax from the radio, and check for continuity from one end of the center conductor to the other. do the same for the sheild.
ok, coax is good?
good.
using ohm meter check for continuity between the vertical part of the antenna and the mount itself.
should be no continuity.
if there is a short, its the plastic insulator is cracked, misaligned in its hole or not there.
rad shak sells this assemble still i think.
antenna mount checks good?
good.
re connect coax to mount.
check SWR. still high?
make sure of good connections from mount to box, box to bed, bed to cab, etc...
good luck,
matt |
Epson14
Junior Member
Username: Epson14
Post Number: 14
Registered: 3-2006
| | Posted on Thursday, October 26, 2006 - 10:45 pm: |
|
Thanks for all the good tips guys , I will try all these this weekend . Mike . |
Epson14
Junior Member
Username: Epson14
Post Number: 15
Registered: 3-2006
| | Posted on Tuesday, October 31, 2006 - 7:08 pm: |
|
Happy ending to the story , lol . To be honest , im not for sure what did it but I got the ball mount , a new spring an thats it . Kept the same ground . Swr is now below 1.5 .  Thanks again guys . Mike . |
Hotwire
Senior Member
Username: Hotwire
Post Number: 1965
Registered: 1-2005
| | Posted on Wednesday, November 01, 2006 - 11:48 am: |
|
Great news Epson14! You are now fully resonant to 27 mhz!!! Also your gonna love that bandwidth!
Now all you need to do is fashion a tie down clip so you can get through low under passes. Like Taco Bell drive through? 
I found a polyurethene, nylon, ......one of those plastic jobs!I attached to my antenna A plastic clip that I attached a bungee to and hooked to my side view mirror! Think it was called a Gator Clip and it fit the whip perfect!
Kenny
cef491 |
