cb and scanner interference

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rvawatch

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i think there are other people wondering this too, so I figured I'd start a thread about it..

In my truck I have a uniden 5 watt CB with a Wilson 500 mag mount whip w/ a coil, and a GRE psr-500 with a Austin Spectra multiband mag mount. they are both on the roof of my truck at opposite ends. (it is a pickup so its not a very large roof). When listening to the scanner to local digital state police (152 Mhz), it loses reception when I key up on my CB. I know scanners can "overload" causing them to lose signal, but is this actually harmful to the scanner? what about if the scanner is turned off?

Last, what would the best position be for these two antennas on my truck roof? I have an aluminum toolbox in the bed of my truck that I could get a lip mount or something for.

thanks guys.
 

SAR923

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All that happens when you key up the CB is you temporarily desense the front end of the scanner. If you were going to damage the scanner, it would have already happened. Depending on how much range you want from the CB, I'd either have the CB on the roof (max range) or in the center of the toolbox (acceptable range). The other antenna should be mounted in the center of the toolbox or pickup roof. Having both antennas on the ends of the roof gives each one a very poor ground plane, especially when using mag mounts.
 

rvawatch

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the toolbox is aluminum, so it will act as a ground plane, but is not magnetic for the mag mount. what about having the antennas closer together on the roof? or would they mess with eachother? what about if I only used either the scanner or cb one at a time?

so many questions come to mind lol.

thanks for your help.
 

jon_k

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the toolbox is aluminum, so it will act as a ground plane, but is not magnetic for the mag mount. what about having the antennas closer together on the roof? or would they mess with eachother? what about if I only used either the scanner or cb one at a time?

so many questions come to mind lol.

thanks for your help.
Can always get a hole mount there. Or put metal on the underside to make it magnetic.
 

SAR923

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Drill a hole or rig up a trunk lip mount for the tool box. Putting the antennas closer together on the roof will only compound the problem. You'll start to get passive interaction between the antennas even when you're not using the CB
 

freqs

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Drill a hole or rig up a trunk lip mount for the tool box. Putting the antennas closer together on the roof will only compound the problem. You'll start to get passive interaction between the antennas even when you're not using the CB
dont forget to ground the tool box if you are putting the cb antenna on it
 

N1BHH

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As always, the best place for any antenna is on the roof, dead center. In your case, it all depends on what your priorities are. Is your scanning the number one or is the CB? How they are mounted now isn't the worst case scenario. I really would have that CB antenna mounted on the toolbox, as long as it has a spot in the center that doesn't hinge causing your antenna to whack the roof when opened. Just get some grounding of the box to the frame and get a solid mounting spot and you'll have no problems.
 

rvawatch

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there is no need to ground the toolbox though... it is not an electrical grounding that the antenna needs. its a rf groundplane.
 

KK4HG

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Definitely ground STRAP the tool box to the truck bed...then ground strap the truck bed to the cab and frame. Then ground strap the the exhaust to the frame, in two places. Then ground strap the transmission to the frame, then the engine to the frame. One can never do too much strap grounding on a vehicle for RF effect. Just try not to create any ground loops.
 
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