Another high SWR post BUT I have pictures to help with a diagnosis

[DanLP456]

I’m using a Cobra 75 WX ST with a 2ft firestik antenna and medium spring and quick disconnect. No matter how I adjust the antenna SWR remains over 3 on Ch 40. When I extend the adjustable tip to its maximum length SWR gets down to 2.5 on Ch 1. I’m hoping someone can look at these photos of my setup and maybe see something I did wrong? The rubber lining came off the coax in one place but no wires were ever exposed. A missing washer somewhere? And the radio comes in loud and clear on my scanner, so it works. Thank you.

 

[prcguy]

There is virtually no ground plane in your setup and to compensate you can lengthen the antenna some but it will probably never reach a good match. As an experiment attach a length of wire maybe 6 to 9ft long to the ground side of the mount and stretch it toward the rear of the vehicle. If the match suddenly gets better that will back up my claim.

You can cheat and add a capacitor across the feedpoint and a ceramic disc around 50pf at 100v rating is a good start. You should be able to get a near perfect match with somewhere between 25 and 100pf but your range will still be less than if the antenna had some sheet metal below it.

 

[jassing]

1st thing is to use a good swr meter not the one in your radio.
Second, I think using both quick disconnect AND a spring might be too much.
3rd where you've mounted, and only a 2' antenna, you've got a lot "in the way" of getting a good signal.
... and as been pointed out - no ground plane. You can use a NGP antenna (although firestik NGP only comes in 4')

I would move the mount up towards the roof & just use the spring, or leave where is & ditch the spring.
Personally, I found the QD to have far too much play in it to get a reliable signal.

The loss of cable cover could be causing an issue, as it does part insulate...

You could try a grounding strap to the body. A wire or battery cable will not work.

 

[RFI-EMI-GUY]

I am agreeing with PRCGUY. Try his experiments.

But first, is this a new installation?
Is what I see in that damaged coax white oxidation or inner dialectic? The coax might be shot.
That mounting adapter seems to be designed to return a ground, not necessarily a "ground plane" to the antenna at base of the antenna mount. Is this cable kit one of the "no ground plane" mounts FireStik sells? Those "float" the ground at the mounting plate. You might try a normal cable kit that grounds at the mounting point.

 

[jassing]

The firestik NGP antenna is 4' you cannot mix-n-match NGP coax and any antenna.
It does look like one of the "fire ring" cables, but the NGP does not come in firering.

 

[SouthernRoller]

Do you have the fire ring coax and top of the mount or on the bottom? Looking at the pic it appears to be on the top and that wont work.

FireRing Stud Mount Installation

 

[KE5MC]

When I first looked at the picture of the chaffed cable I thought it looked odd. Looking again this morning I realized that the coils disappearing under the lip of something was tight for a coaxial cable. Then it dawned on me it looks more like a heavy duty microphone cable at the transition between the coil and straight part. I have no familiarity with that antenna system. Seems odd for a cable to use for transmitting.

 

[a417]

That does look like coiled mic cable. I'd also redo that rear mount so that pinch point between body panel and bracket doesn't have the cable traversing thru it at that angle.

 

[DanLP456]

Thank you for these replies! Definitely helpful. The frayed cable is actually the microphone cord. I repaired some other sections of it with electrical tape. Never actually saw wires sticking out or frayed. This is a new install, except for the CB itself, recycled that from my old car. I actually don’t transmit on the CB very often, mostly use it to listen. So it’s not going to, like, blow up in my hand or something? lol

 

[a417]

No, i believe the biggest shared concern was that some hack put coiled mic cord inline with your transceiver and was pushing watts down it.

 

[RFI-EMI-GUY]

Do you have the fire ring coax and top of the mount or on the bottom? Looking at the pic it appears to be on the top and that wont work.

FireRing Stud Mount Installation

Even the pictures are confusing. The Fire Ring must have a polarity and though they say "raised shoulder goes toward mounting surface" which makes me think there is no continuity unless the mounting surface has a hole larger than the shoulder. And then what about the insulating washer? This is one of those cases that an ohmeter is essential to make sure the center of the coax goes to the whio, the sheild to the bracket and no connection between the two.

 

[Ravenkeeper]

I’m using a Cobra 75 WX ST with a 2ft firestik antenna and medium spring and quick disconnect. No matter how I adjust the antenna SWR remains over 3 on Ch 40. When I extend the adjustable tip to its maximum length SWR gets down to 2.5 on Ch 1. I’m hoping someone can look at these photos of my setup and maybe see something I did wrong? The rubber lining came off the coax in one place but no wires were ever exposed. A missing washer somewhere? And the radio comes in loud and clear on my scanner, so it works. Thank you.

View attachment 81217View attachment 81218View attachment 81219View attachment 81220

Like others have asked, do you have a good ground between your mount bracket and your vehicle?

From what I can see, your configuration of your antenna on the mount is correct. I used a "stakehole extended mount" for my antenna on my 2015 Silverado. Once I got the bracket grounded to my truck and my antenna properly configured, my SWR was in the mid-1's, and I was talking from one side of Lancaster (CA) to the other, about 6-10 miles. I had a spring one it at one point, but I noticed that my antenna was laying on the bedrail as I was going down the highway, so I removed the spring. I'm running a similar setup/configuration on my 2018 Silverado, with a SUPER DUTY spring.