Understanding Grounded Electricity

[chroot]

Integral,

Hence my confusion. I thought megashawn was indicating the actual antenna itself was grounded to the chassis -- and it's not. You wouldn't be able to pick up radio waves very well at all with a chassis for an antenna. I gave up and stopped participating in the thread.

Certainly you could ground your stereo with the coax sheild, but it's still probably not a very good ground. Ideally you'd like your ground to be as close as possible to the head unit itself; the longer the wire run, the larger your likelihood of picking up alternator whine. The power wire is not very susceptible to noise, because it's regulated and filtered inside the head unit anyway. The ground wire, however, is quite susceptible to picking up noise.

- Warren

 

[chroot]

There's also a good chance that the antenna shield conductor is connected to the head unit's internal ground through a few RF chokes or other power-supply isolation network. Such a network may not be designed to actually carry significant current, and thus may not be adequate to properly operate the stereo. I still wouldn't do it.

- Warren

 

[Averagesupernova]

If you connect the radio to a so-called proper ground, what is there that guarantees you that ALL of the ground current will go through it and not some of it going through the antenna shield? There is NO guarantee. I see it as not that much of a big deal. Most of the time an antenna connector has the shield connected right to the chassis of the radio. Running it through some kind of component is asking for a potential disaster. The reason is because when you have 2 wires running to different parts of the vehicle and both connecting to ground there is a chance (larger than you may realize) that a poor ground elsewhere on the vehicle can cause current to run into the antenna connector and out through the radios main ground. Not too likely any problem will develop when the antenna coax shield is connected right to the chassis during this type of failure but if it were connected to some sort of component, the current would most likely fry that component.

 

[chroot]

Averagesupernova,

What do you mean by "component?" Your argument is precisely the reason the two grounds would be isolated with an inductor or other network. The two grounds may in fact be somewhat different. While you want the two grounds to remain at nearly the same potential, you want your current to flow through only one.

- Warren

 

[megashawn]

it all comes down to misunderstanding, or misexplaining. My apoligies in that regard.

When I was reffering to antenna, I was talking about the entire component, not the individual wire inside that is the actual antenna. As to noise, while my expieriance with it begs to differ, it is entirely irrellevant to my original point, which I have long forgotten by now.

I will try to be more technical in the future

 

[Averagesupernova]

Averagesupernova,

What do you mean by "component?" Your argument is precisely the reason the two grounds would be isolated with an inductor or other network. The two grounds may in fact be somewhat different. While you want the two grounds to remain at nearly the same potential, you want your current to flow through only one.

- Warren

Last I checked an inductor has a relatively low resistance to DC. But NOT likely low enough to pass the kind of current I am referring to without being destroyed. As for a blocking capacitor as part of the network? Obviously megashawns system is able to pass DC through the antenna lead shield or it wouldn't run at all. I've been in the automotive electronics biz and I've seen this sort of thing happen alot. When it comes to connecting grounds that go to several different places you either design the connection so it can carry the type of current I am referring to or you will have lots of defective products due to a failure elsewhere on the vehicle. Most likely megashawn is referring to an aftermarket product and we all know what sort of people CAN end up installing an aftermarket car stereo.

 

[megashawn]

so what sort of person are you calling me? The stereo itself is aftermarket, the antennas are generally factory installed.

I take back my earlier apology. I regret having ever clicked on this topic.

 

[Averagesupernova]

No no no megashawn. I am NOT calling you the type of person that you are thinking of. But we all know a lot of car stereos are installed by people that shouldn't be doing it. If the gear is to stand up it needs to be built to take abuse. We all know that there are morons in every aspect of life. Car audio is no exception. However, it doesn't mean that it is exclusively made up of morons.