No ground plane - Firestick antenna?

[NC1]

I had my next door neighbor ask me about these, and was wondering how this works with no direct, or capacitive coupling (such as a Mag mount), to a ground plane.

I was not sure how to answer the question but did tell him my best guess is that the coax cable is somehow acting as the ground plane, but would do a little research to give him a better answer.

I did notice in one ad that they said the coax cable (specified at 17 feet) will not work with any ground plane antenna, which is how I arrived at my tentative answer.

Can anyone explain how this can work with the mesh shielding not going anywhere? Below are two links to give you a better idea of what I am looking at.

First, the antenna:
https://www.walcottradio.com/firestik-fg4648w-no-ground-plane-cb-antenna-kit-white-p-2588.html

Here is the "magic" coax cable:
https://www.wearecb.com/firestik-k8ngp-no-ground-plane-coax-cable.html

I do have experience with antennas, just not this particular one and my curiosity has the best of me.

 

[RFI-EMI-GUY]

I had my next door neighbor ask me about these, and was wondering how this works with no direct, or capacitive coupling (such as a Mag mount), to a ground plane.

I was not sure how to answer the question but did tell him my best guess is that the coax cable is somehow acting as the ground plane, but would do a little research to give him a better answer.

I did notice in one ad that they said the coax cable (specified at 17 feet) will not work with any ground plane antenna, which is how I arrived at my tentative answer.

Can anyone explain how this can work with the mesh shielding not going anywhere? Below are two links to give you a better idea of what I am looking at.

First, the antenna:
https://www.walcottradio.com/firestik-fg4648w-no-ground-plane-cb-antenna-kit-white-p-2588.html

Here is the "magic" coax cable:
https://www.wearecb.com/firestik-k8ngp-no-ground-plane-coax-cable.html

I do have experience with antennas, just not this particular one and my curiosity has the best of me.

In my opinion it is a bad solution. RF current flows on the coax all the way to the transceiver. Maintaining VSWR is tricky. It can only create problems for nearby equipment. Also it can pick up vehicle noise .

I recommend drilling a hole in the vehicle roof and installing a Larsen NMO-27.

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[NC1]

I recommend drilling a hole in the vehicle roof and installing a Larsen NMO-27.
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If it were going to be a mobile installation, then I would agree. However, my neighbor was entertaining the idea of mounting one of these on a short pole on his back porch.

I know there are far better solutions than that, but we were both wondering how it worked without the shielded braid connected to anything.

I did receive a reply, and apparently the shield is acting as a matching network due to the specific cable length.
Don't know why that concept didn't enter my head at the time, but that makes sense.

 

[RFI-EMI-GUY]

If it were going to be a mobile installation, then I would agree. However, my neighbor was entertaining the idea of mounting one of these on a short pole on his back porch.

I know there are far better solutions than that, but we were both wondering how it worked without the shielded braid connected to anything.

I did receive a reply, and apparently the shield is acting as a matching network due to the specific cable length.
Don't know why that concept didn't enter my head at the time, but that makes sense.

The cable is acting as a counterpoise. He would be better off with a ground plane antenna instead.

He could buy TWO firestick whips by themselves and mount then as a center fed dipole with standard coax. That would be a better solution. There are instructions on the web to do exactly that.

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[NC1]

He could buy TWO firestick whips by themselves and mount then as a center fed dipole with standard coax. That would be a better solution. There are instructions on the web to do exactly that.

That was my original suggestion to him, but with two 102" whips, and I think that's the route he will go.
We were just wondering what flavor of voodoo Firestick was trying to push with their "no ground plane" claim.

 

[RFI-EMI-GUY]

That was my original suggestion to him, but with two 102" whips, and I think that's the route he will go.
We were just wondering what flavor of voodoo Firestick was trying to push with their "no ground plane" claim.

The Fire stick no groundplane has always been hokey in my opinion. The feedline "match" arrangement is subject to so many variables that maintain decent VSWR is going to be a hassle. Using two whips center fed provides a counterpoise that is easily tuned, and and less dependent upon routing of the feedline.

Whichever direction he goes, some sort of balun or choke at the feedpoint would even further improve the match and radiation pattern. There is no shortage of center fed dipole theory and construction advice on the internet and ARRL handbook. Joe Carr published several antenna books that can serve as practical advice.

My first CB base antenna was a simple quarter wave groundplane fed with a 50 foot run of RG8 coax. It matched with low VSWR and worked very well. It was on a 10 foot mast up on a TV tripod.



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