"No Ground Plane" system on metal vehicle?

[madvillebirdman]

I have an old 1990 Toyota 4X4 Pickup and have plenty of ground plane but last week I bought a Wilson 4' No Ground Plane Fiberglass Antenna Kit (it's the one with the slide SWR adjustment up by the radio connection). Usually these antennas are for fiberglass/non metallic vehicles or those lacking sufficient ground plane. Anyway I mounted the aluminum bracket back about 3" from the left taillight, I have no bumper or tailgate so I had a perfect flat surface to mount the bracket. The only metal to metal are the screws going through the bracket. I ran the 17' NGP cable that I wrapped in plastic conduit all the way up the frame and into the cab. The plastic conduit ends right at the slide SWR adjustment. I set the SWR a couple times and finally got about 2.0 on channel 40 and 1.5 on channel 1. Channel 19 is right at 1.0.
I can pickup transmissions from Canada to South America and beyond. I live in Jacksonville Florida and the local signals darn near blow me out of the cab!
Of course I'm only transmitting the legal 4 watts but I just wondered if anyone else had this good a signal using NGP systems on metal vehicles?
It picks up better than my 30' Solarcox on a 50' tower! I'm amazed.

 

[dudmuck]

All i can say is: something must be wrong with your solarcon base antenna.

 

[madvillebirdman]

All i can say is: something must be wrong with your solarcon base antenna.

Yea, the base coax is dry rotted and full of cracks and holes.
It was only for comparitive purposes. If I rewired my tower I'd pickup and transmit darn near anywhere.
I'm just shocked at how well the mobile NGP antenna picks up being on a vehicle with plenty of metal ground plane. I was always told an NGP system would not pickup well close to metal. Half the antenna is 3" away from metal surface.

 

[W5LZ]

It seems like the antenna you're comparing to isn't exactly in the best shape in the world. I would be surprised if a mobile (or any) antenna didn't at least match it's performance.
The 'No Groundplane' type antennas are sort of misleading. They may not use a vehicles metal body for the 'other half' of the antenna, but you can bet that they do use something for that 'other half'. In most cases, that other half is the feed line. And since your vehicle does have a metal body, I would assume it's being used too. Maybe in a 'round-a-bout' fashion, but still being used. If it suits your needs, then why not?
- 'Doc

(Put a new feed line on that base antenna anyway.)

 

[madvillebirdman]

It seems like the antenna you're comparing to isn't exactly in the best shape in the world. I would be surprised if a mobile (or any) antenna didn't at least match it's performance.
The 'No Groundplane' type antennas are sort of misleading. They may not use a vehicles metal body for the 'other half' of the antenna, but you can bet that they do use something for that 'other half'. In most cases, that other half is the feed line. And since your vehicle does have a metal body, I would assume it's being used too. Maybe in a 'round-a-bout' fashion, but still being used. If it suits your needs, then why not?
- 'Doc

(Put a new feed line on that base antenna anyway.)

The new antenna instructions say the ground is through the cable running back to the radio. I have even added plastic conduit around the entire rubber coated "tin" cable and an aluminum non-metallic mount for the antenna. The only metal ground is at the CB itself through the negative battery ground. The antenna I replaced was a 6' whip grounded at the body and frame. Even at near perfect SWR the whip was no comparison to this Wilson 4' NGP.

 

[Moleculo]

only metal ground is at the CB itself through the negative battery ground.

and the negative post on the battery is probably grounded to the vehicle's frame, making the whole vehicle part of the ground plane.

If it's working good, don't change it

 

[super20dan]

so it recieves good but how does it talk?

 

[zygoma]

Some of the NGPs are helically wound vertical dipoles and are actually fed at the center by having the coax go up through the center of the fiberglass mast and then solder to the ends of the antenna windings. That's how it's done on marine VHF antennas.
On UHF, Maxrad makes an endfed halfwave NGP that works at "unity gain" (0 gain) when used without a ground plane, but gives about 2db gain when used over a ground plane. I use their MAX-4302 for ham stuff on my van and for a in-hotel-room antenna.
Larsen (or whoever they are now) has (or used to have) a VHF gain antenna where the coax was part of the matching system, and the installer was instructed not to cut off any excess. At the antenna end, the coax disappeared up into the base of the coil, and the coil had a molded flange on it with 3 screw holes. A perfect SWR was hard to get on that antenna, too, but it was a good compromise for mounting on the ends of pipes and driving light tabs and Bobcats and stuff.
My guess is that the antenna you've got, even though it doesn't need a GP to work, will still work better if it has one under it. And I agree that your base installation sounds like it couldn't be worse off if you were using a piece of wet string for feedline at the moment
HTH
-- Zygoma in North Carolina --

 

[rabbiporkchop]

no ground

That antenna is only no ground if it is on a bracket that is electrically isolated from the vehicle, with the ground wire attached to the ungrounded bracket, effectively making it a mobile dipole. If your mounting bracket is grounded to sheetmetal, then you wasted your money, and it is working just like a firestik antenna.

 

[rabbiporkchop]

Ungrounded bracket. Stupid spell check.