I wanted to install a CB antenna on my X that I could fold down easily so I could get in my garage. I also did not want to drill, cut, or in any other way permanently alter Daddy's little X.

Here is my solution. I bought 38.5" of electrical conduit (galvanized) threaded at both ends. I also bought 2 pipe-hanger clamps that clamp the pipe and can then be screwed into something - usually used to hang plumbing pipes.

I took the front two screws on the plastic stock basket out of the roof rack, and used two 6mmx30 screws to replace them. I screwed the pipe-hangers into the rack over the top of the basket, and then clamped the pipe into them.

So now I've got a pipe running across the middle of my basket. That's fine.

Then I take this quick-release aluminum antenna mount and hand-screwed it onto the pipe. I slapped my new Firestik II antenna into it and set about tuning the SWR.

My SWR is in the toilet. Through some expirementation I discover that if I isolate the antenna mount from the pipe it's mounted on with electrical tape my SWR is fine.

This is weird though. My understanding was that you WANTED your atenna mount to have a connection to the metal body because it provided a ground plane, and that was needed?

As I have it now, the antenna isn't grounded at all. Although the radio itself is.

Have I just misunderstood the need for the antenna to be grounded?

Thanks.
Hedron

pics ?? we love to see pics

Couldn't tell you anything about the ground plane but an ez-over on the antenna would have been very simple to install.

You must ground the antenna.

You must ground the antenna.[/QUOTE]

Thanks Ian, that is what I thought but I didn't want to pass on miss information and screw up someone's new radio.

Ok, so then if I need to ground the antenna, the question becomes this: "Why is my SWR through the roof and the only way to make it go down is to un-ground the antenna? What am I doing wrong?"

And sorry, no pics. I don't have a scanner or digital camera. The EZ-Over btw (which I saw on Ian's site) looks like a great solution but I couldn't find it to buy anywhere local and don't have time before my trip to order it and get it in.

Thanks,
Hedron

There are two types of grounds with a transmitter system. RF ground and electrical ground. An antenna can function without the mount being attached to ground because the RF siganl will inductively couple to the flat plane of metal (roof) beneath the antenna. Depends on antenna design. The SWR is the key to your success. If it goes up when a ground is attached then that is indicative of having a difference in ground potential between the electrical and RF ground. So if SWR's are better without the second ground attachment, go with it. This discussion goes round and round here. To qulaify myself, I have been an Extra Class amatuer operator for 16 years, hold a General Radio Operators License and a degree in EE. Take it for what it is worth and have fun.

What is your call?

Thanks for the information and confirmation of what I have been doing. I had a similar experience as the person who started the thread (although with a different antenna mount). I originally had the antenna bracket clamped to the lip of the hatch. I had a good SWR of between 1.2 and 1.1. The antenna was clearly grounded in this set up. When I moved the mounting location to the cross bar on roof rack (which I understand is *not* grounded as a result of at least the plastic/rubber connection between the cross-bar and main rail), I added about a one foot length or wire to ground the antenna to one of the hatch bolts. My SWR was up over 3. When I removed the ground wire, the SWR was back to between 1.2 and 1.1. I have run it without the ground wire for several weeks now with no ill effects.

k_enn

I've got a new theory on this. See how this grabs you.

1)I figured out the same thing as you - the roof rack isn't grounded. But it's the whole rack as near as I can tell, not just the cross-bar, although initially I assumed it was grounded.

2) Because the roof rack isn't grounded, when you attach an antenna to it, and it makes an electrical connection to the roof rack, it actually USES the rack as a part of the antenna somehow. This creates horrible SWR. Ungrounded metal attached to an antenna = more antenna? Like wrapping aluminum foil around your TV antenna years ago? Although really it's a fat hunk of metal attached only to to the mount and the coax ground, not to the antenna itself. Still, it's in there somewhere!

3) So what you had when you grounded your antenna was you had a big fat piece of roof rack in the circuit maybe, PLUS the ground?

4) I have yet to test this but I will tonight. Here is my theory on what should be done. Isolate the antenna from the roof rack (electrical tape or whatever) and then ground the antenna with a grounding wire to the frame.

Goofy? Implausible? I dunno, but I'm gonna try it.

Hed

Theory on isolation...

Maybe try a piece of rubber/insulation and use it between the rack and the antenna mount. maybe 1/8 or so thick..make small strips and add until the SWR gets to a good reading with the antenna grounded.

I am about to go shopping for my CB antenna and was going to mount it onto the roof rack using clamp hoses and a piece of aluminum.. but wanted to insulate it from scratches and isolate it from the rack.
Here is what someone posted for me a few weeks ago, and was going to try something like this

Superjens web page

Let us know how is goes and what you found.

Good luck
Joe

I note form SuperJens' site that he did *not* insulate the antenna bracket from the roof rails and he did *not* use a separate ground wire for the bracket. So much for grounding to the truck instead of the rack?

k_enn

My call is N9PO

Maybe I am in left outfield here? But my Firestick II is a Non ground plane antenna. So it needs no Ground, correct? My SWR runs about 1.2 all the way across.

If you are thinking of the model of antenna that comes to my mind, if it is a "no ground plane antenna" then that means that the design is such that there is an element or coil built into the antenna to complete a balanced antenna. Correct the ground is not needed for RF tranmission, and the anti static ground is completed throught the radio circuit.

Nah. Mine is a FS series antenna. This is from the Firestik website: "The "FS" antennas are compatible with autos, trucks, vans, motorcycles and ATV's in a single antenna configuration when metallic ground plane is available."

Last night yielded erratic results. More info when I find a more identifiable pattern.

Hed

This seems relevant, by the way:

http://www.firestik.com/Tech_Docs/Mnt-Grnd.htm

But I think there is something else going on here, because I DEFINITELY grounded the damn thing last night (continuity check and all) and it didn't really help.

Hed

More info from my Tech Head brother:

"If as one of the other messages indicates the roof rack is not grounded you end up forming an unbalanced dipole when the conduit is in electrical contact with the roof rack. This is a "bad thing."

When you isolate the conduit with electrical tape, the antenna mounted in the middle causes it to from an approximately quarter wave ground plane. RF ground is provided through the shield of the coax and balanced by the conduit. This gives you much better SWR and is perfectly OK.

Sounds like you've got a solution. Just bear in mind that you do not want an SWR above about 1.5 if you can help it. Also you want your lowest SWR at channel 20 and channels 1 and 40 should be approximately equal SWR. If 40 is higher shorten the antenna, if 1 is higher lengthen it."

I'll let you all know when it works.

Here was the stupid resolution to the bad SWR readings described above.

I moved the antenna from the middle of the pipe to the driver's side. Boom, the SWR's went good.

I did NOT isolate the mount from the conduit. I did NOT isolate the conduit from the roof rack. Neither of those things seemed to do anything helpful on a consistent basis.

The SWR's only cleaned up when I moved the antenna over. I believe this has something to do with the relationship to the ground plane.

After I fixed the SWR's I went ahead and grounded the mount and grounded the far end of the conduit - it didn't hurt anything and it seemed like a good idea.

Weird, eh?

Hed