Discussion in 'Mobile Radio Systems' started by KG4HNY, Dec 10, 2012.
tailgates and tire carriers grounding problems are made worse by rust, grease, dust, oxidation...
A good DC path doesn't make a good path for RF. RF flows on the surface of a conductor, not through it. So whilst a certain diameter of cable may be good at shifting 20A of DC, it has very little surface area in comparison to say flattened braid from RG213.
Look at this picture
Measuring the resistance between the tailgate and body of my two year old Ford Mondeo it was 72 Ohms. Remember that this is across an all metal hinge with bolts that go directly to the tailgate and the body of the car on a car that is only a couple of years old with rustproofing and no corrosion. After I added some grounding straps it was zero ohms.
It's all coming together now....
I plan on mounting my radio under the passenger's seat with the faceplate up above the rear view mirror. How important is strapping the seat frame to the tub? Or even the radio to the tub or seat frame somehow?
I wouldn't mount the panel above the rear view mirror.
In some states, that's not even legal (like here in CA, where the laws are very specific about where you can mount things around the windshield -- even a small GPS cannot be mounted there; you must mount one in the lower right or lower left corner of the windshield and nothing near the center if it's above the dashboard) but even where it would be permitted, I don't like the idea of mounting anything around "head height" that could become a flying object in a collision.
Another issue is the LCD displays, when they get "hot" from the sun, can go "all black" and you can't read them. That doesn't really damage them, as they work okay again when they cool off. But on a sunny summer day, mounting anything where the sun can shine on it can cause the "no display" problem.
I'd mount it down lower.
And mount securely. Even the parts that are under the seat. Again missiles in a wreck. Don't mount anything under the dash on the drivers or passengers sides. In a wreck you'll slide forward and down before the belts catch you. I have a 4 inch scar on my knee that came from an external speaker that was mounted to the side of my center console. 3,000,000 miles accident free in a big truck, but I tore the hell out of a hot rodded 1979 Olds Cutlass once. Something I'll never forget.
A Jeep seatbelt should not let you slide forward. This is a serious gripe I have with all the factory seat belts. I don't know what they were thinking. You may have small collision-like forces once every ten years in most vehicles, but if you are putting your Jeep to use, you may have ten a year (or more). Having everything tight and secure is mandatory.
The seat is always important because like the above tailgate, it is mounted on a hinge. But, it only matters if there is reason for RF to be flowing through the seat bracket. If you run a strap from the radio to the tub, you are bypassing the entire seat bracket assembly.
Yes, this is the plan. I plan to use the tub as the main component of my bonding with everything else branching from there. As for the sun problem, I have the top and doors off most of the summer. I will look other places, but above rear view mirror may be some of the only shade I can get.
What will you do when you put the windshield down? That's always a concern of mine.