FlexyJK

So i have been having issues with my CB lately. I am currently running the Cobra 75 and have the control box under my glove box. I ran the coaxial along the door jam to my mount(picture attached). My antenna is a tunable firestick. I'm not sure of its height but it is pretty long. As i was testing with the SWR meter i was in the 5 range. So i swapped my coaxial to a 30ft for when i had my CB mounted above the windshield. And i got a reading closer to 3. So could my issue be with my cable? Or do i need to ground my mount better somehow? The mount is painted but i left the area around the antenna bare.

Rbzak

Have u tried adjusting the tip on ur antenna? Do u have a volt meter that has a continuity function on it. U need to check to see if there is a short in the spring, cable, mounting stud and the antenna. And check to see if u have a good ground on the mounting bracket.

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TURTLECON

18' should be plenty. Are you using an external SWR meter or the built-in on the cobra?

FlexyJK

I did try adjusting the tip, but it still stayed right at about 3. And for the ground i have it on a metal tab to body where the tailgate hinges usually go. Should i run some sort of grounding strap? And thanks for the tip on checking the continuity, i didnt think of that.


I borrowed an external and followed some online instructions. Im guessing i should start by buying a new 18' cable.

Rbzak

U might try adding a ground wire to it. Just to see what happens.

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arjeeper

This is almost always a "grounding" issue, which is to say, the mount and connection of the mount to the vehicle is not allowing it to use the body as the counterpoint or ground for the vertical monopole, what you'd call the antenna.

If the coax is good and the different lengths cause different SWR readings, that means the system is using the coax as the counterpoise rather than the body/frame of the vehicle.

Try to scrape off some paint on the back of the mount (side against the body of the vehicle) and scrape some paint off the body that faces the part of the mount that you scraped off. This should allow a clean electrical connection and should also be a better RF connection.

You might try a little dielectric grease where you scraped it too.

FlexyJK

Could i have the antenna out together wrong? I have the plastic washer then a metal washer then bracket then metal washer then the spring?

arjeeper

Though there is a common "rule" that coax should be 18' for a CB, that "rule" only came about due to so many poorly grounded systems.

In a well-grounded system, the coax length is irrelevant as it's not part of the antenna.

Only when the coax is acting as the counterpoise (bad, but common) would the length matter.

FlexyJK

Thank you for the info. I will try and mess with the mounting point tonight. I was wondering how it all worked. Thanks.

TURTLECON

The plastic washers should be closest to the hole on the bracket.

CB ground is different than electrical ground. You shouldn't need to scrape any paint so long as there's a decent connection between the antenna mount bracket and the frame of the vehicle (not the body).