ANother question on antenna

[Frank]

I bought a car antenna which requires the base to be grounded to
the car's body. I wanted to know what would happen if I would
connect the antenna ground all the way back to the battery
ground, not the car's body. Would this cause bad radio reception?
I am wondering because it is currently grounded next to the
antenna hole on the fender, and I am getting some static in FM
reception at location in the city where I do not with other cars.

TIA

[Chad Wahls]

Frank wrote:
> I bought a car antenna which requires the base to be grounded to
> the car's body. I wanted to know what would happen if I would
> connect the antenna ground all the way back to the battery
> ground, not the car's body. Would this cause bad radio reception?
> I am wondering because it is currently grounded next to the
> antenna hole on the fender, and I am getting some static in FM
> reception at location in the city where I do not with other cars.
>
> TIA

Not worth it.. As long as it gets in good to the sheet metal you will
be OK... It's not a high power ground. The body of the car works as a
ground plane for the antenna, more for AM than FM. Going to the
battery and insulating the antenna from the body will actually make it
worse... It's an immediate area thing. Going to a ground point close
to the antenna mount is best if you feel necessary. If it is an
aftermarket deal check your coax, ground to metal, and proper antenna
length... no celly look alikes, rubber ducky ****, just a good 'ol ss
or at worst telescoping power antenna if you are a radio buff :)

[Joe Kesselman]

Static may be a loose connection; check your wiring. Or it may be that
the car has some other piece of equipment which is generating static; on
my old Honda I had to install a power-line filter.

[Arny Krueger]

"Frank" > wrote in message


> I bought a car antenna which requires the base to be
> grounded to the car's body.

That's probably done so that the car body can be part of the
ground plane for the antenna.

> I wanted to know what would
> happen if I would connect the antenna ground all the way
> back to the battery ground, not the car's body.

It would probabaly decrease the signal strength from the
antenna.

> Would this cause bad radio reception?

Depends on the circumstances. At long distances from the
transmitter, undoing the intended ground plane could hurt.

>I am wondering because it
> is currently grounded next to the antenna hole on the
> fender, and I am getting some static in FM reception at
> location in the city where I do not with other cars.

FM reception in cities is prone to that. This effect is
dependent on the directivity of your antenna. The
directivity of most car antennas is partially dependent on
the shape of the sheet metal around them. Is this antenna
mounted in an atypical spot on your vehicle?

[GregS]

In article >, "Frank" > wrote:
>I bought a car antenna which requires the base to be grounded to
>the car's body. I wanted to know what would happen if I would
>connect the antenna ground all the way back to the battery
>ground, not the car's body. Would this cause bad radio reception?
>I am wondering because it is currently grounded next to the
>antenna hole on the fender, and I am getting some static in FM
>reception at location in the city where I do not with other cars.
>
>TIA
>
>

It is a ground loop, but you have to use it. Well you don't really.
Try it and see how things work!

greg

[Frank]

"GregS" > wrote in message
...
> In article >, "Frank"
> > wrote:
>>I bought a car antenna which requires the base to be grounded
>>to
>>the car's body. I wanted to know what would happen if I would
>>connect the antenna ground all the way back to the battery
>>ground, not the car's body. Would this cause bad radio
>>reception?
>>I am wondering because it is currently grounded next to the
>>antenna hole on the fender, and I am getting some static in FM
>>reception at location in the city where I do not with other
>>cars.
>>
>>TIA
>>
>>
>
> It is a ground loop, but you have to use it. Well you don't
> really.
> Try it and see how things work!
>
> greg

What is a "ground loop"? Can you explain what is does? Thanks!

[Laurence Payne]

On Tue, 20 Sep 2005 21:46:20 -0400, "Frank" > wrote:

>I bought a car antenna which requires the base to be grounded to
>the car's body. I wanted to know what would happen if I would
>connect the antenna ground all the way back to the battery
>ground, not the car's body. Would this cause bad radio reception?
>I am wondering because it is currently grounded next to the
>antenna hole on the fender, and I am getting some static in FM
>reception at location in the city where I do not with other cars.

We can spout theory at you. Or you can try. Car electrics are a
Black Art. Let us know your result?

[Scott Gardner]

On Wed, 21 Sep 2005 19:13:12 -0400, "Frank" > wrote:

>
>"GregS" > wrote in message
...
>> In article >, "Frank"
>> > wrote:
>>>I bought a car antenna which requires the base to be grounded
>>>to
>>>the car's body. I wanted to know what would happen if I would
>>>connect the antenna ground all the way back to the battery
>>>ground, not the car's body. Would this cause bad radio
>>>reception?
>>>I am wondering because it is currently grounded next to the
>>>antenna hole on the fender, and I am getting some static in FM
>>>reception at location in the city where I do not with other
>>>cars.
>>>
>>>TIA
>>>
>>>
>>
>> It is a ground loop, but you have to use it. Well you don't
>> really.
>> Try it and see how things work!
>>
>> greg
>
>What is a "ground loop"? Can you explain what is does? Thanks!
>

A "ground loop" is a term used when not all components are grounded to
the same "reference voltage". We usually refer to ground as being at
zero volts.

As an example, let's say you have a car where the head unit is
grounded under the dash, the antenna is grounded at the fender, the
amplifier is grounded to a bolt in the trunk, and the engine block is
grounded via a grounding strap connected between the engine block and
the car's chassis. The negative terminal of the battery is connected
to the car's chassis as well.

In a perfect world this wouldn't be a problem, because every component
has a path to ground:

Sparkplugs and alternator - through the engine block to ground strap
to the chassis, then from the chassis to the battery via the other
ground strap.

Antenna - fender to battery via chassis strap

Head unit - ground wire in harness to chassis to battery via chassis
strap

Amplifier - From the bolt in the trunk, through the chassis, through
the chassis ground strap to the battery.

In reality, you can run into cases where not all of those "grounds"
are at the same voltage, because of poor/loose/missing connections or
corrosion. For instance, if the ground strap between the engine and
the chassis is missing, the engine components may still be grounded
through the engine mounts, but the connection might not be as good.

These small voltage differences cause stray currents in the ground
wires, and cause your components to pick up radiated noise from things
like the ignition, alternator, turn signal flashers, air conditioning
blower, and windshield wipers.

Ground loops are tricky, because some installations may work fine with
a different grounding location for every component, while others can
pick up radiated noise from something as simple as an extra ground
path between the chassis of the head unit and a metal bracket behind
the dash.

To minimize the possibility of ground loops, I usually run one
heavy-gauge ground wire from the battery back to a distribution block
in the trunk, and *all* of my amplifiers, equalizers, signal
processors, and the head unit get grounded to that one distribution
block. I leave the antenna ground alone, for the reason that the
other posters have mentioned. I also upgrade the battery-to-chassis
and engine-to-chassis ground straps using the same heavy wire that I
used between the battery and the distribution block.

Also, don't mount audio components directly to the metal chassis of
the car. Instead, mount them to a board, and then bolt the board to
the chassis. This will prevent the component from having two ground
paths (one through the ground wire and another through the chassis of
the component).

This may seem like overkill, but the first time you spend hours
tracking down radiated engine noise in your stereo, a single-point
grounding scheme like the one I described starts looking pretty
attractive.

Scott Gardner




--
Scott Gardner

"Clothes make the man. Naked people have little or no influence on society." --Mark Twain

[Richard Crowley]

"Frank" wrote:
>I bought a car antenna which requires the base to be grounded to
>the car's body. I wanted to know what would happen if I would
>connect the antenna ground all the way back to the battery
>ground, not the car's body.

Why? For RF purposes, the body serves as the counterpoise
(i.e. "ground"). Making it run a long distance back to some
other place likely will degrade the performance of the antenna.

> Would this cause bad radio reception?

I would bet that it will.

>I am wondering because it is currently grounded next to the
>antenna hole on the fender, and I am getting some static in FM
>reception at location in the city where I do not with other cars.

What is the manufacturer's recommendation for how to ground
it? I would think that using a toothed lock washer on the under-
side of the mount will connect to the body metal right at the hole.
I surely would NOT install long runs back to other places. This
is RF and even more critical at FM (~100MHz) frequencies.

[Richard Crowley]

"Laurence Payne" wrote...
> "Frank" wrote:
>>I bought a car antenna which requires the base to be grounded to
>>the car's body. I wanted to know what would happen if I would
>>connect the antenna ground all the way back to the battery
>>ground, not the car's body. Would this cause bad radio reception?
>>I am wondering because it is currently grounded next to the
>>antenna hole on the fender, and I am getting some static in FM
>>reception at location in the city where I do not with other cars.
>
> We can spout theory at you. Or you can try. Car electrics are a
> Black Art. Let us know your result?

Car "electrics" are one thing. This is a VHF-RF question. Long
ground runs are not a good idea. Neither of these newsgroups is
really likely to get you a good answer. Suggest trying a newsgroup
where VHF antennas are discussed. (Perhaps one of the ham
newsgroups.)

[GregS]

In article >, "Richard Crowley" > wrote:
>"Laurence Payne" wrote...
>> "Frank" wrote:
>>>I bought a car antenna which requires the base to be grounded to
>>>the car's body. I wanted to know what would happen if I would
>>>connect the antenna ground all the way back to the battery
>>>ground, not the car's body. Would this cause bad radio reception?
>>>I am wondering because it is currently grounded next to the
>>>antenna hole on the fender, and I am getting some static in FM
>>>reception at location in the city where I do not with other cars.
>>
>> We can spout theory at you. Or you can try. Car electrics are a
>> Black Art. Let us know your result?
>
>Car "electrics" are one thing. This is a VHF-RF question. Long
>ground runs are not a good idea. Neither of these newsgroups is
>really likely to get you a good answer. Suggest trying a newsgroup
>where VHF antennas are discussed. (Perhaps one of the ham
>newsgroups.)

The subject refers to ground which is shared by RF and power. The
power ground is what we were mainly interested in. I don't
know if any head units have an isolated antenna input. One could couple the
antenna to ground with a small capacitor instead of directly DC coupling it.

greg

[Bruce Chang]

"GregS" > wrote in message
...
> In article >, "Frank"
> > wrote:
>>I bought a car antenna which requires the base to be grounded to
>>the car's body. I wanted to know what would happen if I would
>>connect the antenna ground all the way back to the battery
>>ground, not the car's body. Would this cause bad radio reception?
>>I am wondering because it is currently grounded next to the
>>antenna hole on the fender, and I am getting some static in FM
>>reception at location in the city where I do not with other cars.
>>
>>TIA
>>
>>
>
> It is a ground loop, but you have to use it. Well you don't really.
> Try it and see how things work!
>
> greg

That's not a ground loop. There is no loop. There's no circuit to allow a
loop in an antenna.