Mobile Whine Noise

[fmulder13]

Hey all, sorry to beat a dead horse, but I've looked all over these forums and haven't found a scenario similar to mine yet.

I've got a RS Pro-2056 connected to an AS 1/4 wave VHF antenna that's NMO mounted to the roof, with an external Motorola speaker that's got an 1/8" plug soldered onto it. From the very beginning of this install I've had this whine coming through the speaker. The whine is rather high-pitched, and will change in pitch with the engine revs, when my blinker blinks, and when i turn things on like the A/C.

Here's what I've tried: It used to be wired to the fuse box. That changed yesterday when I hardwired it to the battery. The red wire is now going directly to the positive terminal of my battery, and the black wire I've tried grounding to numerous places in the interior with no luck yet. The problem got slightly better when I disconnected the grounding wire for my CB from the chassis. The red wire for the CB went to the fuse box, and I've had no noise problems with the CB, just fyi. I've found that if I play with touching the black wire for the scanner to various spots on the chassis I get absolutely no change in the whine.

I should also mention that I've got a device to hook my iPod up to the stereo system that connects to my cd changer port, and requires a grounding wire. Right now it's grounded in a spot kind of close to where the scanner was grounded, but manipulating that really doesn't do a whole lot. I drive an 03 Civic, and could probably answer any questions for anything I left out. Thanks in advance.

 

[fineshot1]

OK - two things I can suggest for you.

1. You have to run both the positive and the negative power wires to the battery posts
or as close to them as you can hook up to. The battery acts like a hugh filter capacitor
in this configuration and can help in suppressing mobile alternator noise & other noise.

2. Those Motorola speakers are usually about 3.2 or 4 ohms and most of the audio
amp outputs on scanners like to have 8 ohms hooked up to them. With a 4 ohm
speaker almost any noise seems louder or comes through the audio amp easier. I
would suggest you try a true 8 ohm speaker and see if that also makes any difference.

Good luck & please post back your results.....

 

[K4DHR]

Try disconnecting the antenna from the scanner, opening up the squelch, then starting the car. If the noise is largely or completely gone, then the noise is coming in through the antenna. If its still present, try connecting the scanner to another power source independent of the car's electrical system. Usually a 12v .5A wall wart works with most of those RS scanners.

As far as power wiring is concerned, articles I have read seem to suggest that creating a common ground for your mobile devices is more important than running them back to the battery, provided that you have a good chassis ground. I would suggest wiring the positive wires to both the scanner and CB to a common location, such as a distribution block. I have my equipment wired to the post leading to the high current fuse box under the hood. It is an easy, convenient connection and is only about 12-18" from the battery itself. Then, make sure the CB and scanner share the same ground and preferably use one of the manufacturer's grounds under the instrument panel. This will minimize ground loops as much as possible.

 

[fmulder13]

OK - two things I can suggest for you.

1. You have to run both the positive and the negative power wires to the battery posts
or as close to them as you can hook up to. The battery acts like a hugh filter capacitor
in this configuration and can help in suppressing mobile alternator noise & other noise.

2. Those Motorola speakers are usually about 3.2 or 4 ohms and most of the audio
amp outputs on scanners like to have 8 ohms hooked up to them. With a 4 ohm
speaker almost any noise seems louder or comes through the audio amp easier. I
would suggest you try a true 8 ohm speaker and see if that also makes any difference.

Good luck & please post back your results.....

Just tonight I connected red and black wires to the positive/negative terminals, respectively. (To the right ones, too!) The red wire I had to extend by about 4 inches using a 4 inch wire and a cap. The black wire went right to the negative terminal. The noise got worse, which really makes no sense to me.

I should mention that I didn't go directly through the firewall. I routed the power wire behind my glove box, and out by the passenger side door. The wire is still protected from the elements, and the wire isn't taut, nor does it appear to be in any danger of being worn down. Am I breaking any noise rules there?

 

[AK9R]

The most common sources of vehicle-generated noise are generally:

1. Alternator - often a high-pitched whine that varies with engine speed.
2. Spark plugs - generally a pulse noise that varies with engine speed.
3. Fuel pump - a whine that is mostly constant.

Tracking down any noise source in a vehicle can be a real headache and you have to be persistent and methodical. As others have mentioned, the integrity of the power wiring is usually the first solution people go for. However, I didn't see your answer to K4DHR's question. That will help us determine if your noise is coming in through the power wiring or the antenna connection. That's the first step on the process of elimination.

 

[fmulder13]

Alright, tried disconnecting the antenna, and got the same whiney results, so it looks like it's definitely the power leads. Also, interestingly enough, I found when I took a little road test today that the whine will vary in volume at completely random times. The only consistency I found was that when my RPMs were the lowest, a sort of pulse noise like what W9RXR was describing took over the whine. When I would accelerate once more the whine replaced the pulse again. More to come....

 

[fineshot1]

It sounds like you routed the +12vdc power wire near the vehicles computor which may be the problem.

Try finding out if the vehicle computor is near the power wires. If so re-route the power wires as far
away from that as possible.

What make/model/year vehicle is this?

 

[fmulder13]

It's a 2003 Honda Civic

 

[fineshot1]

It's a 2003 Honda Civic

OK - I have no experience with them. I do a lot of installs in american models
such as Ford CVPI's, Expeditions, Explorers & Dodge Durango SUV's & pickups
and a few others.

Keep plugging away as you seem to be following a good pattern of isolation
and following the symptoms and I agree that it could also be fuel pump related
as well.

 

[AK9R]

The pulse noise you are hearing at low engine speeds might point towards spark noise as the source. I'm not familiar with Honda engines. Does the engine have a distributor with spark plug wires going out to the spark plugs? Or does it have a "coil on plug" ignition?

One easy trick you can try is to make sure the hood is grounded to the rest of the body as that might help contain any spark plug noise. Get a short piece of at least 12 or 14 guage stranded wire. Braided ground strap wire would be better, but you may not have any available. Find a screw on the hood and one nearby on the body so you can electrically connect the hood to the body. You may have to scrape some paint off from under the screw to get a good connection. And make sure the wire won't get caught in the radiator fan or an accessory drive belt when the hood is closed.

 

[socalmike]

Try this.

http://www.popularmechanics.com/how_to_central/automotive/1272491.html

Hi,

It sounds like alternator noise to me but read the entire article in the above link. Most mobile scanners already have a circuit consisting of a coil and capacitor that connect in-line with the power to filter the vehicle power. I know the Unidens used to. If you open the scanner and see what looks like a small transformer (actually a coil ) and a large capacitor the circuit is there but more filter , rather suppression is needed . Most Stereo shops will carry an array of filters and supressors you can try.

let us know how it turns out,

mike

 

[K4DHR]

Coil on plug noise tends to be radiated, thus coming in through the antenna. I've been having to fight this with my Mazda 3, it looks like my solution is going to be shielding the coil packs themselves.

A pulsing noise at low engine speed is probably the fuel pump, though in modern FI vehicles, the computer can raise the speed of the pump to increase the pressure, as the old fashioned, fuel rail mounted fuel pressure regulators have largely gone away.

Ferrite beads will be the most effective way at controlling the noise coming in through the power leads. At a minimum, place them at where the power goes into the fuel pump, power leads to the coil on plug modules, and the radio itself.

 

[fcfd988]

I run a Radio Shack PRO-2066 in my vehicle. It is powered up in the console along with my other radio equipment. It always produces alternator whine. It doesnt matter if there is an external speaker used or not. None of my other equipment in the vehicle (Kenwood commercial radios) produces the whine. This same scanner did this in the previous vehicle it was installed in as well. I have just written it up as a poor design and gotten used to it.

Wes

 

[SLWilson]

Grounding....

I know that there is a ground wire coming out of the scanner. I had a similar issue with my 1988 Chevy Blazer and a Uniden scanner.

What I finally was able to do to get rid of it was this:

1. Find a GOOD ground as close to the scanner as you can and run your ground wire to it.

2. In addition to the ground that is factory supplied out of the scanner, find a screw and attach ANOTHER ground wire to the scanner chasis.

3. Lastly, where your antenna connects into the scanner, run a ground wire to it too.

I know it sounds like overkill. But, it worked for me after weeks of pulling my hair out. What a techno guy finally thought was that the internal factory ground "might" have been bad or somehow ran through something it shouldn't have and was causing a ground interference loop. I have no idea other than doing what he said (as described above) straightened mine out...

Steve/KB8FAR

 

[af5rn]

Nothing wrong with overkill, so long as it works! Wire and screws are cheap!

 

[KC0QNB]

if you still have the whine after you do all that stuff, try this.
http://www.crutchfield.com/App/Product/Item/Main.aspx?g=181150&i=003S15A&search=noise+filter&tp=2653

 

[fmulder13]

I know that there is a ground wire coming out of the scanner. I had a similar issue with my 1988 Chevy Blazer and a Uniden scanner.

What I finally was able to do to get rid of it was this:

1. Find a GOOD ground as close to the scanner as you can and run your ground wire to it.

2. In addition to the ground that is factory supplied out of the scanner, find a screw and attach ANOTHER ground wire to the scanner chasis.

3. Lastly, where your antenna connects into the scanner, run a ground wire to it too.

I know it sounds like overkill. But, it worked for me after weeks of pulling my hair out. What a techno guy finally thought was that the internal factory ground "might" have been bad or somehow ran through something it shouldn't have and was causing a ground interference loop. I have no idea other than doing what he said (as described above) straightened mine out...

Steve/KB8FAR

Crazy enough that it just might work!!

With this being the only device in my car that's behaving this way, I gotta figure that there's something in the device itself that's exacerbating the problem.

Quick question, though. How would you suggest finding a really good ground?

 

[SLWilson]

Seat bolt

Crazy enough that it just might work!!

With this being the only device in my car that's behaving this way, I gotta figure that there's something in the device itself that's exacerbating the problem.

Quick question, though. How would you suggest finding a really good ground?

If you can loosten a seat bolt or have screws holding a console to the floor (under the carpet probably) that is the best ground INSIDE/close to where you have the scanner probably....

Steve/KB8FAR

 

[N1BHH]

I have always grounded the radio to as nearby a chassis ground connection as possible. That usually stops the noises before they even start to happen. Any excess wire you have connected to any power source can be wrapped around a snap choke. I have seen them at Radio Shack and many electronics stores. These help greatly as well. I will soon be installing my newly purchased Alinco DR635T and that comes with very long leads, so, I'll be picking up a few snap chokes.
http://www.radioshack.com/search/index.jsp?kwCatId=&kw=snap choke&origkw=snap choke&sr=1