Antenna Placement

[David Williams]

So, I recently got my Weboost 4G-X with a 12 in. aftermarket antenna. I wanted to ask you guys about the placement of the antenna on my vehicle. I have a 2007 Toyota Camry with hail shield. As you can see in the picture, the hail shield has a lot of heavy duty metal in its frame. I've been thinking that I'll put the antenna on the trunk because I don't have 12 in. diameter metal plate on top of the hail shield for the antenna to stick to. So, if the antenna is on the trunk, will the metal on the hail shield and its proximity to the antenna reduce the strength or efficacy of the antenna/amp? Should I attach a flat metal sheet to the top of the hail shield for the antenna to be on so that it's above all the metal of the hail shield? If more detailed pictures are needed, just let me know.

Cheers,
David

 

[Nick Copeland]

Trunk will be fine. WeBoost says you only need at least a 3x3 area for a ground plane. The only small issue you might have on the trunk is if you're in an area with less towers is if the front of the car is between the antenna and the nearest tower you may see some null but, it won't be that much of an issue. You will really only notice that in a very rural area. It is more of an issue with amateur radios when your antenna is on the trunk and the front of the vehicle is between you and the repeater if it is distant. Ideally the center of the roof would be better so you can get a full omni-directional coverage. The hail guard won't cause any RFI, at least it shouldn't. You could put it in the center of the roof and have the antenna stick up through it. Shouldn't bother it to much. You can test it both ways and see which is better. Ether or would be fine and the hail guard shouldn't bother it.

 

[Marc R. O'Leary]

My antenna sits near the rear of my wagon and sticks up through a tube steel roof basket. I've never had any issues. Its routed this way so wires can pass thru rear hatch seals, as my door windows are all frameless, so in driving rain, some moisture can get in between wire and glass. Hatch seals around wire fine, and keeps wires out of door openings.

 

[Mark Blue]

Is there a sunroof in your car under the hail guard? If so, the more separation you can achieve between the external and internal antennas the better off you'll be as far as oscillation is concerned. You'll have to follow the install guide and tinker around a little to find what works best for your setup. Having the external antenna too close to the sunroof can sometimes cause this to happen. It'll be interesting to see how you like it once you're in the field.


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[David Williams]

Is there a sunroof in your car under the hail guard? If so, the more separation you can achieve between the external and internal antennas the better off you'll be as far as oscillation is concerned. You'll have to follow the install guide and tinker around a little to find what works best for your setup. Having the external antenna too close to the sunroof can sometimes cause this to happen. It'll be interesting to see how you like it once you're in the field.


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No sunroof. I'm thinking the antenna on the trunk will work. If it doesn't, I'll toy with different places... maybe I'll install a small plate on top of the hail shield if I can't find a spot that works.

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[James Hammett]

I use a no ground plane (NGP) antenna so I can get it up above any obstructions and not have to worry about ground plane issues. With a trunk mount the signal will be blocked to towers ahead of you. Not uncommon since towers are often located right along the highway you're travelling on. You want the antenna up as high as possible to clear obstructions and a trunk mount won't help you there.

 

[David Williams]

I use a no ground plane (NGP) antenna so I can get it up above any obstructions and not have to worry about ground plane issues. With a trunk mount the signal will be blocked to towers ahead of you. Not uncommon since towers are often located right along the highway you're travelling on. You want the antenna up as high as possible to clear obstructions and a trunk mount won't help you there.

Could you give me an example of the NGP antenna?

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[James Hammett]

Wilson makes a good one (aside from gain on the xLTE band which won't matter in rural areas): https://www.wilsonamplifiers.com/rv-trucker-spring-mount-antenna-kit-w-mount-318433/

Or for a more stealth look check out the Laird Phantom.

 

[David Williams]

I attached the Wii boost amp and found that I still had 2 red blinking lights. I called the support line and they said the antennas were too close. So, I put a plate on the hail shield to attach the antenna above the plain of the shield. Unfortunately, I still have the 2 red blinking lights after building the plate. Ugh! Hopefully I can figure it out while chasing tomorrow.

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[Mark Blue]

Or for a more stealth look check out the Laird Phantom.

Now your speaking my language James. So nice and compact, and the magnet on the base is gorilla strong. The GB8U base with the TRA6927M3NB antenna is the setup I run.





You may opt for something taller than what I use though.


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[Nick Copeland]

Wilson makes a good one (aside from gain on the xLTE band which won't matter in rural areas): https://www.wilsonamplifiers.com/rv-trucker-spring-mount-antenna-kit-w-mount-318433/

That is not really classified as a NGP Antenna or (System). It uses radials attached to the loading coil that is halfway up as the ground plane. That is what those metal rods are that is shown in the picture on that product page. If you look under the "Product Features" it says "Built-in Ground Plane" which in this case are those radials you attach to the loading coil. That is why it says "No ground plane required" because the ground plane is built onto the antenna with the screw in radials. Generally speaking most antennas need some sort of ground plane if it be radials or a metallic surface of a vehicle. The only time you would use a NGP system is when your vehicle has little or no metallic surface area for the antenna to use as its NEEDED counterpoise. A true NGP system is one they uses nether and the antenna and coaxial cable are a matched set. So it is pretty much a last resort if your mounting it with no metallic surface if limited surface area I. E. boats, campers or those with fiberglass or wooden surfaces etc. You see NGP systems more in Chicken Band trucker setups which have firesticks on their side mirrors. In this case this is not an issue as you can use an antenna with radials or one without where the vehicle can supply a sufficient ground plane or you could use both. In this kind of situation a NGP system would be irrelevant since their are different options for ground planes and antennas.


@davidduncanw where is your external antenna mounted in reference to the internal?

 

[David Williams]

That is not really classified as a NGP Antenna or (System). It uses radials attached to the loading coil that is halfway up as the ground plane. That is what those metal rods are that is shown in the picture on that product page. If you look under the "Product Features" it says "Built-in Ground Plane" which in this case are those radials you attach to the loading coil. That is why it says "No ground plane required" because the ground plane is built onto the antenna with the screw in radials. Generally speaking most antennas need some sort of ground plane if it be radials or a metallic surface of a vehicle. The only time you would use a NGP system is when your vehicle has little or no metallic surface area for the antenna to use as its NEEDED counterpoise. A true NGP system is one they uses nether and the antenna and coaxial cable are a matched set. So it is pretty much a last resort if your mounting it with no metallic surface if limited surface area I. E. boats, campers or those with fiberglass or wooden surfaces etc. You see NGP systems more in Chicken Band trucker setups which have firesticks on their side mirrors. In this case this is not an issue as you can use an antenna with radials or one without where the vehicle can supply a sufficient ground plane or you could use both. In this kind of situation a NGP system would be irrelevant since their are different options for ground planes and antennas.


@davidduncanw where is your external antenna mounted in reference to the internal?

The internal antenna is on the right side of the driver's seat. The external is on the rear section of the hail shield as far away from the internal as I could possibly make it. The picture in my previous post shows the external antenna on the square sheet metal on the rear section of the roof hail Shield.

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[Nick Copeland]

@davidduncanw Ok just wasn't sure from the pic if it was the front or back of the car. Your placement is ideal and you have the 6-8" separation that WxBoost recommends. Not sure why you're getting de-sensing between the two.

A couple of things to try just for trial and error. Place the stock antenna where you currently have the antenna sited and see what happens.

After that move it to the center of the vehicle if you can and do the same test with both antennas and see what the outcome is for both tests including the one above too.

Just a coupe things to try to narrow down some things.

 

[Gordon Hudson]

Here's an interesting image which shows the performance (reference 0dB) impact which results from different mounting locations.
Of course, every application will show some differences from this test, but it's interesting nonetheless.



Ground planes should ideally be a half wave in diameter. Transmission loss increases rapidly if the diameter of the ground plane is reduced below a tenth of a wavelength.

A no ground plane antenna often uses the shield of the coaxial cable as the ground plane, and so ships with a certain length of coaxial cable. Cutting the length shorter can impact the performance of the antenna.




Gordon, N5GOR

 

[Nick Copeland]

That is a very useful chart. I am going to have to save that. I would have never guessed a NMO would have more loss than a mag mount on the trunk or even have the same loss as a trunk lip mount. It is a good illustration of how surface area comes into play for your ground plane.

Good catch on the length of the cable on the NGP system. I left that out in my explanation of it and forgot to mention that part of how its matched.