Why the spiral pattern on Radio Antennae and Grid on Windshield?

If I am not mistaken the wire wrapped around the antenna has somthing to do with the keyless entry system, your remote.

And the little black dots in the front windshield are maybe perhaps the instant defogger, if your car is equiped.

Heh, the "spiral" you see is used to reduce wind noise and the black dots are part the black band around the perimeter of the windshield to protect the adhesive from the sun.

Steve

Incorrect statements so far: "The wire is wrapped around to make for a longer antenna." "The dots are the XM radio antenna." "The wire wrapped around is for the RKE." "The black dots are an 'instant defogger.'"

Why are people insistant on guessing? Do some research.

Like I said: "Heh, the "spiral" you see is used to reduce wind noise and the black dots are part the black band around the perimeter of the windshield to protect the adhesive from the sun."

But I will narrow down my statement a little bit. The "sprial" on GM antennae are to reduce wind noise, probably the same for other manufacturers, but can't be sure.

Steve

Hey I just guessed, never really wondered myself, I know my Jimmy has that on the antenna and on the windshield, but I never gave thought to it that was just the first things that came to mind.

What adhesive?

thxs

"Steve Mackie" wrote:

The adhesive that holds the windshield on the car.

Spend a little time studying antenna design and you might find that you need to revise your opinion in favor of scientific fact. Read some of the antenna manufacturers literature, or cut an antenna open. The spiral wire is for the AM radio band.

Its part of the tint.

You have got to be kidding me. *sigh*

THE SPIRAL YOU SEE WRAPPED AROUND YOUR AUTOMOTIVE ANTENNA IS THERE TO REDUCE WIND NOISE.

Just confirmed that not only has GM done so, Mitsubishi as well. Here's a quote from Mitshubishi's website:

"....identify an aeolian tone noise from the pole antenna. Subsequently, generation of the noise was restricted by using a wire spirally wrapped around the antenna. The diameter of the wire is 0.2 times the diameter of the antenna."

Here's a link to the article:

Now how about a quote from the SAE website?

DaimlerChrysler's Peter Gladysz, a Senior Manager in vehicle development and synthesis says, "Daimler- Chrysler's NVH lab works on all platforms simultaneously, so if anything can be utilized cross-platform - like going to a spiral cut antenna to stop whistle noise - it spreads throughout the product line-up"

Here's a link to the article:

Now, I say to you: "Spend a little time studying antenna design and you might find that you need to revise your opinion in favor of scientific fact."

Steve

The spiral wrap on the car antenna is there to reduce wind drag &

stop antenna 'whip motion'. The German's used this feature on WW2

submarine periscopes to stabilize 'periscope viewing'. With the spiral

wrap, antennas could be made smaller diameter & still resist wind/water force

without bending nor vibrating much in the breeze.

the same is correct for metal chimneys like the ones they have in oil refineries

Andreas

Correct answer BUT wrong method of repair. The spiral is actually cut into the stainless shaft that the antenna is made from. The end ball and the mounting screw fitting with locktite are then pressed on. Then it goes through a wash and pretreat and then through a powder coat booth. Ford and Chrysler were the first to use the spiral cut to both reduce wind noise and to reduce antenna harmonic motion due to wind drag. GM followed VERY shortly, The only real drawback is the spiral cut antennas are not as strong as the standard shaft units and they make lousy window breakers ( take a course on EMS vehicle extrication for that neat trick ) because of it.

Oh and if you own a Ford or Chrysler with a fixed antenna it was probably made in Amsterdam NY by Ward Products. The chrome or black spanner nut securing it was produced by Manth/Brownell near Kirkville NY. It was also painted by either WW Custom Clad or Sumax powder coaters. And at least 30,000 of them were scrapped after WW had a fire that damaged the coating after they were processed.

All this discussion is fine about how the shaft is cut but it doesn't explain the wire wrapped around the outside of the shaft. I stand by my original posting which is based on standard radio science, try you local library for the ARRL Antenna Book, written in plain language and found in many libraries as it has been used by hundreds of ham operators to understand antennas and to build their own.

No >Correct answer BUT wrong method of repair.

I posted a couple of quotes on why the wire is there. Written in black and white for you to read without going to a library. We are not talking about ham radios, we are talking about automotive antenna, and THE WIRE IS THERE TO REDUCE WIND NOISE.

As for the dots, the OP will have to take a picture and send it through to give an answer. He didn't say "group of dots at the upper center of the windshield," he said "the grid of black dots on the upper portion of the windshield." With that, I can guaruntee that 99.9999999% of black dot patterns on windshields are part of the black band provided to protect the adhesive from the sun.

Steve

There is NO WIRE. The spiral pattern is cut in the steel of the antenna. NO WIRE wrapped around it.

As for the dots it depends on which dots and where. There are positioning marks on most windshields for the bots to use when they place the glass in the frame. There are also the ones that are printed to block the adhesive around the edges.

Don't need any antenna books.

Read up on it, some are cut and some are wire wrapped.