no ground plane coax

[nino]

I have a new vehicle with a fiberglass roof. I bought a lil wil and cannot get any betta than 1.5 to 1, so i want to go to a no ground plane antenna. my question is this: is a ngp coax no more than an 18 ft piece of coax with a different connector setup? This is what it seems to b and i need to know if anyone has any expertise in this area.

[whitestick]

no ground plane coax ??? - well thas a new one on me - and i have been doing this and ham for 30+ years - can we have pictures of this "new " type of coax please - sounds like snake oil to me

there is no such thing - what they are doing is "tuning " the antenna AGAINST the coax - using the BRAID as a form of counterpoise - NOT GOOD !! - yes it will work - but at best a compromise solution and certainly not really effective

you say fiberglass roof on your vehicle ??? - i take it the rest is metal ?? - what sort of vehicle ?? car - RV - truck ??? - please specify

what sort of mounting are you using ??

come back with the above and i may be able to advise - as i used to run a fibeglass vehicle AND cb many years ago

[nino]

it is a 2011 mitsubishi outlander. i used a setup somewhat similar to this with a pontiac transport and got a great match, but i used regular coax and the little plastic insulators so the ground was not actively hooked up. now wilson and francis have ngp antenna kits and supposedly regular coax wont work. my lil wil is on a 4 in wide band of steel around the tailgateand gets a 1.6 match, but that is too high for my toy which is why i am after a lower match.

[doughboy]

What is the steel band grounded to anything can it be grounded to the frame so the antenna can use the frame as a groundplane a strap is probably not enough still just kind of a counterpoise situation

[nino]

it is part of the vehicle structure, but is not enuff for a ground plane. i am using a magnet mount lil wil on it, but it is the onlly spot on the roof that is accesible steel. even the luggage rack is composite to save weight

[whitestick]

ah so you are compounding things by using a mag mount - just go's from bad to worse - IF you want this setup to work in ANY way effeciantly - you are going to need to provide some sort of ground plane - which will entail some work - either by fitting a aluminium plate in the roof lining + some heavy strapping to the chasis of the vehicle and then fitting a proper through mount antenna ( what i did to my fiberglass vehicle ) or maybe get /make /fit some sort of antenna support to your chasis ( sort of like a tow bar without the ball ) and mount a decent antenna on that

also you may wish to read through this :http://www.wc7i.com/reflection%20section.htm as you seem to be somewhat confused about the TRUE nature of SWR - see in particular the conclusions at the end

hope this helps

[nino]

an interesting read, but there has to b a better way than ripping out the interior of my 28000 new truck! the lil will does not work horribly but i just dont want to encounter problems while talking skip. Barefoot i have talked 10 to 15 mi. line of sight.

[doughboy]

Is the whip in the little will all the way down which is usually the case with small ground plane if so you may be able to snip a half inch of the whip and get the swr a little lower

[Biotpolice]

I too have a varient of this vehicle. Here in the K we have the outlander 2, the Peugeot 4007 and the Citroen C crossser. I have the citroen. I had no idea the roof was plastic until trying a magmount.

I have tried a diamond/Watson tailgate mount but get rfi in the vehicle speakers at 70 watt, well at an output really.

I have tried roof bars with mount on there and an earth wire to tailgate mounts.

Then i moved my tuner to a cubby hole in the trunk and made a counterpoise of wires and pulled up the foldaway seat and shoved them in there. This was earthed to the foldaway seat mount and linked to antenna mount.

Then the coax feed coming in i changed to mini 8 low loss and made a coiled choke of about 6 turns around grease can (4 inch) and secured with cable clips. I placed this in cubby hole. Mistake as we want rfi outside of the vehicle.

In summary my grounding is poor and i have not found an adequate solution.

I would be keen to know how you got on or any photos of mounts etc.

Thanks
Robert

[Biotpolice]

Another suggestion given o me was removing headlining and filling it with aluminium foil. Flat earth bonding of fuel pump and exhaust system. I am not sure how effective this would be though. Next time ill buy a truck to suit the rig. Shame though as his vehicle is quite a capable off roader. Better than you would have thought.