What is this for?

Explained here... in 1970 AM was probably 97% of what was listened to in automobiles...

 

We talked about this before. http://mmb.maverick.to/threads/whats-this.89234/

 

.......

 

I suppose the little "teeth" on the tab will eventually cut through the paint.

 

if it would have been needed it would have been a "ground strap"...

 

I suggest that you spend the week-end reading up on Maxwell's equations, a physics book on magnetic and electric field theory, Faraday effect, etc. (Just messin' with ya - I work in electrical and mechanical engineering)

In short: a perfect "ground" will have a 0 (zero) potential. The radio (and everything else) uses the chassis as THE ground. If the "ground" is not perfect, that implies that there is a voltage potential. Static voltages (regardless of how they are generated cause all kinds of issue. What you hear as "static" on the radio are arbitrary and unintended changes in voltage from some source (other that the intended source). The static voltages can also enter through the +12V. Way back (when I was young and foolish), I had a radio in the car that my friends called an "Audio Tachometer".
A lot of the early auto computer issues were (are) caused by static & noise on the +12 line, AND being picked up on the sensor lines. Sometimes "miss-fires" of after-market ignition systems are the result of wires too close to the spark plug wires, or ignition coil.

 

It was on T-Bird... Low end vehicles got the tab...

Go ahead and make fun, basically shows your ignorance and/or willingness to learn...

 

still doen't explaine why a hood needs a "radio" ground. I'm willing to learn is why I am still waiting on an answer. I don't see one on the trunk lid...

 

It's been well explained, apparently you aren't reading the posts... If you just can't understand I'm sorry...

And yes the trunk is grounded, through the torsion springs that support it... Probably would not make a difference though, as the trunk is far enough from antenna that any static generated by vibration would likely not be picked up... Hood is like what?? Four inches from antenna??? Again the hood also acts as a shield between antenna and ignition system...

 

Threw mine away

 

Ha Ha - "ain't it the truth"!

 

Believe!

 

AM radio works in a different manner than FM, too. FM is pretty much straight-line and the further you get away, the weaker the signal. AM "bounces" in leaps that are 40 miles or so, IIRC. On a cold, clear night, shortly after I got my Comet and it still only had the factory AM radio in it, I picked up WLS out of Chicago! 1300 miles away!

 

I understand how the AM radio broadcasting works.
still not clear...why the hood has to be poorly grounded...
if a car had a rear mounted antena, would the trunk have this grounding tab?

 

A bad spark plug wire will really mess with an AM broadcast. I would put stock in what was said above about a lot of the equipment underhood being possible interference sources.