Dual band antenna mounting on roof rack.

[gary in ohio]

[
.....fold-over ability for entry into low overhead clearance areas. Power rating is 200/200 watts. The connector type is a gold-plated UHF/PL-259. Black finish. Grounding is not required."

Where did you find Grounding not required? I have yet to find a referance at any vendor or diamond's web site that say this is a Ground less antenna.

From a functiona; standpoint the antennas will be grounded, through the mount and/or coax. Now you may not need a ground plane but you will need a ground to the antenna.

 

[tdesanto]

I have yet to find a referance at any vendor or diamond's web site that say this is a Ground less antenna.

Gary, the statement I placed in quotes and the link I provided (Here's ) is from a vendor.

Also, what do you take the statement "ground independent antennas" on Diamond's own site to indicate?

 

[gary in ohio]

Also, what do you take the statement "ground independent antennas" on Diamond's own site to indicate?

The working is odd, Maybe a translation issue. Normally they will say no ground plane is required. Those are found on many boat antennas and antennas for fiberglass vehicles. If they are not requiring a ground then They are using the coax as part of the antennas. I dont like that idea. Its not that hard to get a ground plane on most vehicles.

 

[tdesanto]

Agreed, but how much is it really necessary at these frequencies?

For example, how much of a groundplane does an HT have?

I'm still new to this and I'm trying to learn as much as I can. I can tell you this much, it has worked great for me. Last year in a caravan of multiple vehicles, all with 2m/ 70cm radios, I was the 2nd to last vehicle in the group and I was the first to pick up another truck that was heading our way and was still over 10-15 miles out. That might have as much to do with my antenna's location or height as anything else, but I continue to be impressed with it.

On another trip with a friend who's got a less than stellar antenna installation (location is not as good, mounted to the tire carrier and doesn't extend above the roofline much), I never had to use more than 5w for him to hear me, but he had to transmit at 25 and 50w many times just to get a signal out.

 

[mk4]

Gary, the statement I placed in quotes and the link I provided (Here's ) is from a vendor.

Also, what do you take the statement "ground independent antennas" on Diamond's own site to indicate?

I wouldn't qualify expedition exchange as an accurate source of information regarding the antenna. A look at Diamond's website reveals that they don't make such a claim.

Also, what do you take the statement "ground independent antennas" on Diamond's own site to indicate?

That's in reference to the mount. There are ground independent antennas, such as a j-pole, loop antennas, dipoles, balanced antennas, etc... So yeah, it's possible to put one on the mount.

 

[gary in ohio]

Agreed, but how much is it really necessary at these frequencies?

YOu can build an antenna that doesnt require a ground plane that is easy, Its called a dipole. You feed the antenna from the middle. Most mobile antenans are fed as long wires from the end of the antenna and the coax or the vehicle body acts a the 2nd 1/2 of the antennas. At VHF and UHF freq the plane doesnt need to be large only 19" on 2m.

For example, how much of a groundplane does an HT have?

A HT actually has a fairly large but poor ground plane, Its called the human body, You will also see people selling "rat tails" for handhelds and they are
use for to improve range. Before handhelds went micro size a good hand held radio had enough metal and legth that it provided a pretty good counterpoise for the antennas. Now a days they over come the antenna loss with higher power

I'm still new to this and I'm trying to learn as much as I can. I can tell you this much, it has worked great for me. ...... I was the first to pick up another truck that was heading our way and was still over 10-15 miles out.

Antenna location, gain figures, coax quality, terrain and radio all contribute to range, the 10-15 miles is a minimum I would expect. I commute 50miles to work each day and routinely talk with other mobiles 20+ miles away on simplex and can talk 50 miles mobile to a base.

 

[AKRover]

The instructions describe the antenna as a "radialless antenna". Here is a quotes from the poorly translated instructions.

"The antennas employ a radialles structure which allows the antenna to work well at temporary fixed station, on bicycle or with hand held transceiver."

The antenna will basically "work" anywhere but that doesn't mean that it will be at it's optimum performance potential.

 

[mk4]

A HT actually has a fairly large but poor ground plane, Its called the human body...

I doubt this, but I'm no RF engineer.

 

[mk4]

The instructions describe the antenna as a "radialless antenna". Here is a quotes from the poorly translated instructions.

"The antennas employ a radialles structure which allows the antenna to work well at temporary fixed station, on bicycle or with hand held transceiver."

The antenna will basically "work" anywhere but that doesn't mean that it will be at it's optimum performance potential.

Did you try grounding your mount/antenna?

Don't overthink this. It's VHF/UHF and it's pretty simple.

 

[AKRover]

Did you try grounding your mount/antenna?

Don't overthink this. It's VHF/UHF and it's pretty simple.

I have bee distracted with other things.

By grounding are you just talking about running a wire from the antenna mount to DC ground? If so isn't the coax shield doing that already?

When I get some time to mess around I think I'm just going to play with the mounting location a little bit and see if that has any effect.

 

[gary in ohio]

I doubt this, but I'm no RF engineer.

Assume a metal case the body will provide some ground plane affect. It is also a big RF block when used while on your belt.

 

[Saratoga]

I take it AKRover that you managed to get the antenna working OK with your Rangie

A friend with a Range Rover Classic has mounted his radio antenna's on the 'scuttle panel' which is (I think) that area between where the bonnet lifts up and the windscreen. The drawback with the RR is that the roof is aluminium so you can't use magmounts and I'm not sure how strong it is either.

I've got a cab roll over cage on my Defender and have the antenna mounted to that, but that cage goes all the way down to the chassis too.