Tuning CB

mattressking

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Alright so I've went through the entire system and can't find my fault so I am reaching out for some help here. Recently installed cb with the following:

Uniden 520xl pro
Firestik 3' adjustable antenna
Firestik ss spring
Firering 9' coax
Wagon Gear front fender mount

I can't get the SWR reading less than 2.2 right now, tried various changes to grounds, large gauge, smaller gauge, grounding directly to battery, no change in that regard. After reading numerous things about swr, tuning, velocity factors and the recommendation of running an 18' coax by Firestik, is that the potential failure? Is running a 9' cable where the recommended length is 18' potentially my problem? I have to order one so I can't easily access one to test, but I'm curious if this is a valid plan to change. I've already tested grounds and hot leads between antenna and radio and everything is working as designed.

The only other item I am thinking about is that I used an available dash plug for the power/ground for the radio itself. Could that pose an issue with swr reading vs going to the fuseblock/battery? Keyed voltage at the plug is ~12.4v.

Thanks!
 

izzyandsue

Izzy
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The power plug can absolutely be too weak for the radio, but first try doing a temporary ground from firestick mount to a good known ground and see if that does it. Using the cigarette plug will cause more interference than not through.
 

mattressking

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The power plug can absolutely be too weak for the radio, but first try doing a temporary ground from firestick mount to a good known ground and see if that does it. Using the cigarette plug will cause more interference than not through.

Tried temporary grounds from firestick mount straight to battery, no change in performance and tried a couple different gauges.

I'll try rerouting power to something more substantial or temporarily hardwire to battery.
 
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Please read what @Darmadude posted. A big failure is where you mount the antenna. I posted an image of transmission pattern on a vehicle. Try the roof and see if it tunes down.

Antenna.PNG
 

MoJ

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My experience has been if you have the following it won’t be an issue:

1. Clean and adequate power. Preferably direct from the battery or through an aux fuse panel that is supplied direct from the battery. However I once used the cig lighter plug with satisfactory results.

2. 18’ coax. Make sure not to coil up any excess.

3. Well grounded antenna.

Several years ago I spent an entire day fighting high SWR. It ended up being a %#$&* bad SWR meter.
 
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I'll share an experience from many years ago, although I'm not sure I understand the physics at play:
3-foot fire stick on the left front fender of my K5 Blazer; Uniden 520XL at the console; power to radio from fusebox inside the cab; cheap SWR meter from Amazon. Truck parked at my spot in the appartment complex, surrounded by 1- and 2-story buildings. Can't get the SWR below 2.5 or so; no way. Then a tip from Kevin Patterson (aka ToolsRUs, God rest his soul...) - "try it where there are no buildings". So I drive out in the open AZ desert for a few miles, and try again - and get it to 1.3 with tuning the screw at the top of the Firestik...
 
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mattressking

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Little behind here. So far, I fiddled with the tuning screw in very minute adjustments and upped the ground lead for mount. Initial test with temp ground leads weren't fruitful but I decided to slap on a bigger ground just to clear the conscience of that, which seems to have worked a bit along with trimming adjustment screw to really fine tune it as best as possible. Got the SWR down to the following:

Ch1 - 1.6
Ch2 - 1.5
Ch40 - 1.7

I'll run this for now, but I'd like to keep fiddling to get it lower. The closest 'open area' isn't exactly a vast empty range so I will bring it along to Colorado and see if I can get some improvements.

Thanks fellas!
 

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