CB antenna mount opinions

[Frdmskr]

Ripping one of the Breedlove or original Motorola (not current wanna be) ball mounts would require removing the panel of the vehicle. I am sure it's happened but really would not want to find out what it took.

As for grounding, there is a huge misunderstanding in your assessment. Instead of the vehicle being an efficient antenna component (as it is with being physically connected) your losses are immense. Your antenna coax (if lucky) then becomes the other half of the antenna. The metal of the truck merely reflects/refracts the radio waves. It's not connected at all.

Look at a Yagi. The driven element is a dipole. It has a hot and shield side. There is usually at least one reflector and one director. They may, or may not, share a conductive boom with the driven element. You will find these parasitic elements effect antenna lobes, nothing more. Take away the shield side of the driven and try the antenna. Doesn't work so well. It'll work, but the losses are horrid. You can hear and be heard but at a fraction of what could be. Same theory here.

Look over K0BG.com which is one of the best sites for looking at vehicle radio system installation. I am sure that mag mount seems great but it's not the best solution.


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[4x4junkie]

I'm thinking you must not understand how a capacitor works like a short-circuit at RF (radio frequencies), or how the bottom of a magnet mount is constructed to function as such when it is placed against the metal panel of a vehicle.

In your analogy with the yagi... if you were to take a capacitor (0.01µF or so, which has an impedance just under 0.6 ohms at 27MHz) and connect it in between where you disconnected the shield from the antenna, you will find... the yagi now works again exactly as it did before (well enough any performance difference cannot be seen in use, and may not be apparent on a SWR meter or analyzer either). It's no different with the 'capacitor' that is formed between the bottom of a magnet mount and the steel of your vehicle's body.

If you want to demonstrate this for yourself, place a block of wood under any magnetic mount antenna and then check it's SWR (be sure to do this on low power!)... Most likely you will find it to be close to infinite since you've effectively "disconnected" it's ground by distancing the mount from the metal of the vehicle.

 

[Frdmskr]

Except the magnets are not part of the circuit. They may have an indirect effect but it is not like a ball mount or NMO where you are integrating the vehicle as part of the antenna. Now, by doing this, you will find that the antenna works much better and more efficiently because its more effectively and efficiently transferring energy.

As I said, the mag mount is not the best solution.

I apologize to the rest of the group we are getting way over there =========>

So I will end with this post by respectfully disagreeing with 4x4junkie on this.

 

[4x4junkie]

Except the magnets are not part of the circuit.

Not sure how you figure that when the whole mount is one with the ground (shield) of your feedline and passes the RF current through to the vehicle's body...
My other vehicle (Ranger pickup) infact has a permanent-mounted antenna on it. If there was this huge loss in efficiency like you say there is, seems I (or those I have gotten signal checks from) would've noticed something by now.

You're right, we'll just have to agree to disagree here. Carry on.

 

[Vegas_Nick]

The mount you show will work fine. I'd go with at least a four ft Firestik or a Larsen NMO mount whip. I do these installations all the time, and yes I understand antenna theory and all that but I also understand practicality and what works in the real world. I'llprobably repeat a lot of what has been said, but here is my take on your questions;

NGP antenna..no, just NO!

Mag mount: I swear by the Wilson Little Wil when it comes to mag mount. You just can't beat it. It really depends on where you will be. Yes, they can be knocked off, but how much wheeling under tree limbs will you do?

Permanent mount: Absolutely the better way to go. The Larsen gives you a 50" steel whip that takes the tree bashing well but it is NMO mount, so it takes a little different mount stud. (You'll have to drill out the mount to fit the the NMO connector) The Firefly is about the best out there next to the Wilson Flex. This is my #1 seller for the installs that I do. It is a great performer. Add a good spring and a Quick Disconnect and you are ready to go.

No matter what you install, you need to tune the antenna to the radio. By all means, if you want to email me with your radio questions, please do! nick@excopllc.com

 

[link30204]

Thanks, I will email you later in the week. Im have a bit of a issue with tuning it but I want to ground the bracket to see if that improves the SWR.

I went with a 5ft fire stick mounted as I posted in the first post

 

[Vegas_Nick]

Thanks, I will email you later in the week. Im have a bit of a issue with tuning it but I want to ground the bracket to see if that improves the SWR.

I went with a 5ft fire stick mounted as I posted in the first post

Awesome. Pickup trucks are always a PITA. The first Tacoma that I did a bed mounted antenna on almost made me a drinkin' man!

 

[AlbanyTom]

Grounding the bracket should help tuning AND make the antenna work better. Short copper wire from the bracket to a clean bare part of the truck. I like those star washers, kind of bite into the metal and get a good contact. That and crimp on ring or spade terminals.

What's your location? Tuning shortened antennas on vehicles can be a PITA. Somebody with access to antenna meter can make that way easier.