No Ground Plane Antenna Fiberglass Body

[Woolyworm]

I've got a fiberglass tub with a steel front.

I'm considering a firestick NGP antenna.

Anyone have experience with these and or an opinion?


Wooly

 

[Lumpy Grits]

More info for you.
http://www.firestik.com/Tech_Docs/GP-or-NGP.htm
LG

 

[Woolyworm]

Planning on driver rear corner at top of tub. I've got a call into firestik as well.


Wooly

 

[Lumpy Grits]

Please post up what you learn.
I have only used NGP on boats and such installs.
LG

 

[Christopher]

I don't know about the firestik. But My jeep has a glass body, and I have a big whip antenna mounted on the passenger rear corner, the ground for it just runs to the chassis. The SWR meter says everything is copacetic. Seems to work fine.
Those firestik antennas sure are popular though.

 

[Woolyworm]

I spoke with firestik today and they recommend the no ground plane antenna kit.


Wooly

 

[Lumpy Grits]

THX for the info.
FWIW: My research was leaning to that also.

LG

 

[Woolyworm]

Sure thing. I'm ordering a Firestick FG4-648 which includes a SS 3 mount, a SS flex spring, a special coax cable and special version of the 4' firestik antenna that work together to create the necessary ground plane. They say they are about 80% as effective as a normal firestik on a metal body so I'm looking to get 2-3 miles out of it.




Wooly

 

[Peanut Butter]

All antennas require a ground plane to work. A NGP antenna creates an artificial ground plane. They were first developed for boating as most boats are fiberglass. Boats typically use a VHF frequency for marine radio. The ground plane required for that is an 18" x18" square of metal minimal. A CB antenna requires a 102" x 102" square piece of metal for it's ground plane. Since a NGP antenna fools the radio by adding a wire for this, it is actually making the antenna a dipole antenna. These antennas work great, just expect some decrease in performance. For most CB use you'll not notice the difference. The point to all of this is the best place to place any antenna is the dead center of a metal vehicle. This allows the signal to radiate out equally in all directions. An antenna placed on the right rear of a vehicle will radiate towards the left front mostly and some to the right rear. That's why a lot of hams put their antennas top dead center of their cars. PS: Just some trivia.

 

[mtnwhlr]

If this is true than how do truckers get away with mounting them on their mirrors?

 

[Lumpy Grits]

If this is true than how do truckers get away with mounting them on their mirrors?

The side of the truck becomes the 'ground plane'.
LG

 

[Woolyworm]

Thanks PB. The mirror mounts are often NGP antennas . Lots of trucks use them since many are fiberglass body with aluminum frame.

Firestik guy I spoke with says ideally you want the ground plane to be 90 degrees to the antenna and within the spread of s 45 degree cone from the tip.


Wooly

 

[Woolyworm]

The ideal spot on a jeep is actually along side the hood. Lots of the Aussie guys run them in the front bumper or grill guard for that reason.


Wooly

 

[Peanut Butter]

If this is true than how do truckers get away with mounting them on their mirrors?

You can mount an antenna any where. Doesn't mean it will work at 100% of its capability. By the way, SWR only indicates the antenna's ability to match the 50 ohms needed at the radio connection. I have antenna tuners that make radios think the antenna is the right ohms. The best antenna however is what we call resonate with the radio. IE: Requires no tuning. Another thing to keep in mind is the amount of power the radio puts out. A CB on AM puts out only 4 watts. If the antenna is not properly tuned it may only reflect 1/2 of a watt back to the radio. The radio has no problem with this and it seems to work fine. The true test of an antenna is to use it at the very outer limits of its range, and then compare it to different locations. You might be surprised the difference placement makes. All antennas have a radiating pattern base on design and location to ground plane. The following are called Smith Charts.

Here is a pattern that shows the antenna radiating in all directions pretty evenly:


While this pattern show all of the power radiating forward with very little going in the reverse and none to the sides:


This can be caused by the type of antenna or the placement of the antenna with relation to it's ground plane. The first is what most want, but the second pattern would be great for highway use.

And it can go even more in-depth than this, but you get the idea.

 

[HackFabrication]

While this pattern show all of the power radiating forward with very little going in the reverse and none to the sides:

That last pattern looks like Yosemite Sam:



“Say yer prayers varmint!”

 

[Woolyworm]

Thanks really funny and a really good match!

Thanks for the info PB.

Here are radiating patterns for different vehicle locations.



I'm not sure what the radiating pattern on a NGP antenna is since it doesn't use the body as a ground plane. The cable is 17' long - I'll have to research cable placement for best reception and broadcast with the NGP.


Wooly

 

[Lumpy Grits]

A SWR of 1.3 or less is good.
Ideal is 1.1 and that is very hard to get with the shorter antenna. Also your SWR will vary some across the channel range.
This was one of the reasons I went with, and still use the 102" 'whip'. As the variance and 'match' was worth it.
LG

 

[Woolyworm]

NGP antenna came today. Looks pretty standard. I think the mast may be a bit beefier than the GP unit. The cable looks the same but is different inside. Everything is high quality and well engineered. I like the hand adjustable tuning tip vs the Wilson's allen wrench type. I got the 4' model. Comes with a heavy duty stainless mount, spring, and all hardware and includes a mic hanger. Loo forward to trying it out.



And my favorite cookie fortune




Wooly

 

[Woolyworm]

Tuned this today. Got it to 1.1 on 20 and 1.5 on 1&40. Pretty damn good!


Wooly

 

[Lumpy Grits]

Very good SWR across the band.
What ANT and components did you end up using?
LG