Grounding NMO

[katt02]

Hi all,

Sorry, kind of new to the whole ham radio thing but I am very confused on this one project. I have a VHF laird nmo mount antenna that I would like to mount somewhere on my roof or chimney, but I am unsure of how to do this. I know that this is not the most effective antenna setup, but it will be temporary for a few months until I get a tri band antenna.

Anyways, How would I ground an nmo bracket mounted antenna from the roof; Where would I attach the grounding cable to the antenna?

Also, If anyone knows what the best kind of cable is to have the least loss around 40 ft long on vhf? I am trying to research this but I am getting very mixed results.

Sorry if this was posted before,

Thanks, Katt

 

[mmckenna]

Hi all,

Sorry, kind of new to the whole ham radio thing but I am very confused on this one project. I have a VHF laird nmo mount antenna that I would like to mount somewhere on my roof or chimney, but I am unsure of how to do this. I know that this is not the most effective antenna setup, but it will be temporary for a few months until I get a tri band antenna.

Maybe not ideal, but we do what we can with the budgets we have. Nothing wrong with that.

Anyways, How would I ground an nmo bracket mounted antenna from the roof; Where would I attach the grounding cable to the antenna?

There are two ways you need to ground this.
One will be at the base of the antenna. Usually these have the NMO attached to a bracket that is mounted to the structure. On the base will be a ring with a couple of ground plane radials.

Running a ground wire (I'd recommend 6 gauge) from the mounting bracket -as straight as you can- down to your ground rod. If you make any bends, they need to be gentle sweeping bends. When you attach the ground wire, do it in such a way that it's not going to work loose or corrode.

You also need to install a lightning protector where the coaxial cable enters the house. This will also need to be grounded to the ground rod.

Proper grounding is important, and you need to follow the National Electric Code on this. That means that you either use the ground rod for your home, or if you have to add one under your antenna, it —must— be bonded (attached) to the home ground rod so they are at the same potential.

You'll also want to ground all your station equipment to the same ground as the antenna.

Also, If anyone knows what the best kind of cable is to have the least loss around 40 ft long on vhf? I am trying to research this but I am getting very mixed results.

"Best" means different things to different people.
You likely cannot afford the best cable, and it wouldn't be realistic anyway.
Without knowing your budget, it would be hard to make a good recommendation.

For VHF at 40 feet, you could look at something like Times Microwave LMR-400. It's pretty good stuff for hobby use, and fairly easy to work with. It'll work well even if you decide to use it for UHF or 800MHz use.
Just make sure you properly waterproof your outdoor connections, and don't let anyone tell you it's not necessary.