| Author |
Message |
    
Simcasing
New member
Username: Simcasing
Post Number: 1
Registered: 1-2007
| | Posted on Wednesday, February 21, 2007 - 6:10 pm: | 
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Hi all, new to the group. I am having swr problems with my mobile setup. 3:1 on ch 1 and 2.9:1 on ch 40. The truck is a Ford F250 crew cab with the antenna mounted to the left front corner of the bed. New 8mini coax and new ground wire installed. Radio is a Magnum 257 and the antenna is an Astatic 1k. Just cannot get the swr to read any lower. Any ideas?? Thanks in advance. Kevin |
1861
Advanced Member
Username: 1861
Post Number: 653
Registered: 2-2004
| | Posted on Wednesday, February 21, 2007 - 6:44 pm: |
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probably too close to cab , or need more grounding |
Tech808
Moderator
Username: Tech808
Post Number: 13073
Registered: 8-2002
| | Posted on Wednesday, February 21, 2007 - 6:57 pm: |
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Simcasing,
The bed on your F250 may not be grounded to the frame.
Run a ground wire from the bed or the antenna mount to the frame.
Also have you adjusted or trimmed the Stinger of the antenna yet?
Lon ~ Tech808 ~ N9CEF
CEF#808 ~ CEF HAM#33 ~ CVC#002
10-10 #61493 ~ 10-10 VP#2688
Tech808@copperelectronics.com
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Simcasing
New member
Username: Simcasing
Post Number: 2
Registered: 1-2007
| | Posted on Wednesday, February 21, 2007 - 11:07 pm: |
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Again, thanks for any info. I have a ground wire from the mount to the frame. Ground off all the paint until I saw shiny metal before bolting it to the frame. I have trimmed about 1/4 inch off the antenna. This trimming brought the swr to its current level. Was 5:1 before. I am adjusting up and down a bit to get the current swr. |
Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 2414
Registered: 9-2004
| | Posted on Friday, February 23, 2007 - 12:21 am: |
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having a ground wire running from the mount to the frame is not even close to enough.
we are dealing with RF ground here, not DC ground.
your truck bed needs to act like a ground plane for it to work right.
make sure you have the mount bolted directly to the bed, and then run ground straps from each side of the bed to the frame, run a strap from the cab to the bed, and from the cab to the frame. always on both the left and right sides. lots of us also ground the doors to the cab and the hood to the body also.
i also agree that the antenna is too close to the cab, and your performance will suffer from it, but you still might be able to get the SWR down if this is your only mounting option.
trust me, grounding is your problem, as long as you are using your SWR meter correctly.
matt |
Vanillagorilla
Advanced Member
Username: Vanillagorilla
Post Number: 968
Registered: 4-2005
| | Posted on Saturday, March 03, 2007 - 11:35 am: |
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I think although your SWR is higher on "1" than "40" you need more trimming. Not to discount what Matt is saying which is very true.
Keep trimming the stinger till you see acceptable SWR on "20" then vary your adjustments as needed.
This again AFTER your sure you've done all you can about reflected signal and RF grounding.
Best of luck!
Hank~CEF559
Northeast Net Control
Eastern Long Island NY
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