high swr with new radio

Its been my experience that swr over a 4 is something other than antenna height bad coax bad mounting new trucks are bad about having a suitable place to Mount the antenna

 

Could be any number of things or a combination of them most likely. First are you taking the reading in an open area (not up against tall buildings etc that may reflect the signal back). Second do you have a good antenna ground? Im guessing the ground will be the biggest issue. Next check the coax to be sure its intact and hopefully your coax isnt a "shorty" meaning your coax should preferably be 18ft long for best performance. Also dont coil excess coax in tight coils,any excess should be in loose loops.

 

If its a ground problem swrs would read the same high number on 40 and 1

 

Id definitely try grounding it then testing again. Then if you still get a high reading Id change coax (never hurts to have a spare anyhows) and see what happens.

 

You have a shorted or open antenna line, stop cutting firesticks. Check the mount first there should be a insulated bushing keeping the antenna mount from shorting to ground, frequently missing or on the wrong side of the mount.

Do not close your antenna line in the door or windwing/window have it ran properly if your not sure how.

Good luck hope this helps.

 

Probably a loose connection in the factory ran cable, there are many screw together connections in the factory cable. I would run a different cable to the mount to test it. By the way once an antenna is tuned on a truck changing radios has no effect, antenna is tuned to frequency not to the radio,

 

My question is simple, did you have a radio hooked to that antenna before you got that new radio?

 

An easy way to rule out the coax as a problem is to connect the antenna end to a proper dummy load instead of any antenna at all. If your SWR is good in that condition, you've ruled out the coax and its connectors as being at fault.

Also, to compare a single run of proper coax to the hermaphroditic rat's nest that's behind the instrument panel on lots of modern trucks, which are supposed to allow your CB, TV, and be-bop radio to the same antenna(s). The little network box(es) are made more to isolate one device from the others, not to optimize your CB's performance.

If your model truck that has the "more metal than most" includes a metal roof skin, there's virtually no mount arrangement that will be able to outperform a properly done install through a hole in the middle (or middle-ish) of the roof. After that, some bonding between the parts of the cab that *aren't* electrically connected to the roof will help enhance the counterpoise that your antenna needs to serve as the "missing half" of the antenna system.

For some ideas about grounding (and the vehicle's DC/battery ground is completely different from the antenna's "ground plane" (counterpoise; the *actual* ground plane is the actual ground over which you drive), check out k0bg.com for lots of real-world, solid suggestions. It's written more from a technician/user's standpoint than an engineer's, so it's pretty easy to understand.

Ridgeline pointed out an important question immediately before this post: was there a properly functioning radio that was hooked to your existing antenna system before your new Uniden, and did that earlier radio produce an acceptable SWR? A hacked radio that's putting out spurs will show high SWR if the antenna is resonant on the right frequency range and is fed spurs and harmonics that are out-of-band. In that case, the antenna serves as a bandpass filter, rejecting the stuff that's out of its design frequencies, and *correctly* indicating a high SWR.

Fortunately, there isn't too much that most tweaknicians can identify in the new Uniden radios to butcher, so if the radio's stock, the problem is downstream from there (from the coax to the rest of the antenna system). And probably the most widespread bugaboo in modern trucks is the lack of an adequate metal counterpoise. That's where feeding a dummy load at the end of the coax instead of an antenna can help quickly narrow down where to look for your problem.

That site k0bg.com can also help dispel "common knowledge" about where an antenna must be mounted to benefit from a counterpoise, magic coax lengths, and the idea that enough big DC wires to the battery's ground terminal will make the antenna work better...... the myths and subsequent debunking are worth a couple of hours' worth of reading while you're wide awake.

Hope that helps,

73