Radio antenna question...

[lspencer534]

What is the purpose of a ground strap on the antenna? I assume it's to protect the radio if the antenna gets struck by lightning. My lazy azz is finally getting around to replacing the antenna that got broken off 6 months ago. I wanted to just connect the antenna cable to the new antenna and leave the motor (unconnected after I extend the antenna) in the trunk.

If lightning is the reason, I shouldn't have to worry about that if the antenna is inside the trunk.

[lspencer534]

ttt just once

[Datawiz]

:waiting:

[Mike Mercury]

you'd typically ground the antenna end of the coax (assuming it's a car radio application) to eliminate electrical noise from entering; due to an open ground.

And some antennas require a grounded surface to be mounted to... to perform properly. You always want to ground the mounting base of an antenna - to the nearest grounding point.

[DJ_Critterus]

Antenna is part of a circuit. Electricity flows through it so it needs to be grounded.

you'd typically ground the antenna end of the coax (assuming it's a car radio application) to eliminate electrical noise from entering; due to an open ground.

And some antennas require a grounded surface to be mounted to... to perform properly. You always want to ground the mounting base of an antenna - to the nearest grounding point.

And what he said :yesnod:

the wire in the middle of the coax is your positive wire. notice how it is shielded and touches no other metal until it gets to the connection for that wire? The wire mesh running between the outer rubber shielding the the white plastic looking shielding around the positive wire is the ground.

[lspencer534]

Okay, didn't know any of that. That means I'll have to put the antenna in "properly" for it to work.

[DJ_Critterus]

Okay, didn't know any of that. That means I'll have to put the antenna in "properly" for it to work.

Yes. that usually helps if you don't want to hear static. Is it one of those electric retractable antennas? If so, make sure you tap it into the power antenna wire on the head unit (usually pink or blue, I believe).

[lspencer534]

Yes. that usually helps if you don't want to hear static. Is it one of those electric retractable antennas? If so, make sure you tap it into the power antenna wire on the head unit (usually pink or blue, I believe).

Yes, it's a power retractable antenna. All the connections are plug-in, so not much chance of connecting it wrong.

[DJ_Critterus]

Yes, it's a power retractable antenna. All the connections are plug-in, so not much chance of connecting it wrong.

Good stuff. that wire should already be run to the antenna area anyway, so yes, plug an play is right. That wire is also another reason for grounding the base of the antenna.

[lspencer534]

Good stuff. that wire should already be run to the antenna area anyway, so yes, plug an play is right. That wire is also another reason for grounding the base of the antenna.

Thanks! :cert:

[mrvette]

A manual/fixed/non automatic antenna body itself will be a solid connection to the center core of the shielded cable, just as if you connected a clip lead or piece of wire to it, the outer shield connects to the typical mounting base/bolt that could be mounted to the car any power antenna has to have a good ground to that base for the motor to run, and you can NOT use that shield to pull power through....grounding at that antenna/motor assy end is for motor power purposes....

and on one of our plastic body vettes, yes, today we could leave the antenna under the body and never miss it, in fact my car was done that way when I bought it, but I don't even have tune ONE in the car now....nothing....

the old antenna wiring is still in the rear, used to have a power antenna...

:dance::seasix:

[ZipZap]

"Ground" is a relative term. It is a reference point for a system. Earth ground is what you want your house referenced to. Think about it as the negative (neutral in the case of ac) side of the battery that powers a system. Your house is referenced against the earth, which provides a huge amount of stability in the case of a transient voltage, like lightning. All of that energy can be absorbed by the huge capacitance of the earth. Your car is sitting on tires, so no luck. If your car is struck by lightning, the energy needs to be absorbed by the battery and electronics. That's bad. However, the good part of this is that the ground around your car is a much better ground than your car itself, so the lightning will likely seek another path to earth ground.

Your radio needs to measure the incoming rf energy against a stable reference in order to process the energy correctly and repeatedly. That's why you tie several components, including the antenna, to the negative side of the battery. While your battery doesn't likely have the capacitance to stand a lightning strike, it easily has enough capacitance to damp out any noise generated by the car that would otherwise interfere with the measurement of the rf signal to the radio.

The trick to grounding in a car is to absolutely minimize the resistance between a ground point and the negative terminal of the battery. Any unwanted resistance in the circuit will cause the ground point to be at a different voltage than the negative terminal, and hamper the stability of the reference point. So the utility of the ground strap on the antenna is to enable the electronics to measure the incoming signal against a stable reference. Hook it up.

[Mike Mercury]

"Ground" is a relative term.............................................................................................................

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