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Author Topic: Alternator Noise  (Read 6153 times)
KD8BIN
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Posts: 12




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« on: June 12, 2012, 04:32:11 PM »

I have read all the posts on this subject, and I have my ID-880H installed in a new vehicle  with the power
leads going directly to the battery. I do have  some whine in the radio, and was wondering what is the bottom line....
leave the ground lead hooked to the battery, or is it better to ground it to the vehicle chasis? I am confused..........

Thanks,
John   KD8BIN
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AA4PB
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Posts: 12793




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« Reply #1 on: June 12, 2012, 05:59:12 PM »

I found an issue on one radio where two grounds was the issue. The negative lead, which was connected directly to the battery, went inside the radio and terminated on a PC board. I had a small amount of alternator whine on Tx and also in Rx (even with the volume fully CCW). I found that when the radio was sitting on the seat with no antenna connected there was no whine. As soon as I connected the shield of the coax or touched the radio to the grounded mounting bracket I had whine. My solution was to ground the negative lead to the radio case just before it entered the radio. This provide a low resistance path for the small alternator currents to bypass the PCB connection and the whine disappeared.

Another option might be to try removing the radio ground from the battery and connecting it to the chassis somewhere near the battery. There are often grounding lugs in that area where other vehicle electronics is grounded. The goal is to eliminate paths for the AC alternator ripple (that is heard as whine) to flow through your radio's grounding connections while at the same time providing a stable low resistance path for the radio's current. Connecting the radio ground to dash components has the potential to cause noisy or intermittent connections as the bolts and such are designed for mechanical connections rather than reliable electrical conductivity (painted surfaces, etc).
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KD8BIN
Member

Posts: 12




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« Reply #2 on: June 12, 2012, 06:39:04 PM »

thanks for the reply.....I think I will try and connect the lead to the chasis near the battery and see if that
takes care of it.....

thanks again,

John  KD8BIN
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W8JX
Member

Posts: 5673




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« Reply #3 on: June 12, 2012, 09:07:08 PM »

Kenwood has long made a in line choke for power feed for radio that I have used for many years in a few vehicles.  It is called a PG-3B. It will remove alternator whine on power feed.
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AA4PB
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Posts: 12793




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« Reply #4 on: June 13, 2012, 11:23:35 AM »

Power line filters work well *IF* the noise is coming down the positive power lead. It won't help if the noise is entering via a "sneak" ground path caused by having multiple ground connections on the radio. In the "typical" installation the radio is grounded to one spot on the vehicle via the negative power lead, to another spot via the radio mount, and to another spot via the antenna coax shield. This opens the possibility for small amounts of alternator currents to flow through the radio on its way to one or more of the grounds.

Ideally the radio would have one, and only one, ground connection to the vehicle. Unfortunately, due to the equipment design this is usually not very practical. It can be accomplished as a temporary test to determine if this is the problem, however. Put the radio on the seat (so it is insulated), attach a temporary ungrounded antenna, and see if the noise goes away. Touch the radio chassis to a ground connection and see if the noise comes back.

On the Ford that I had, I put a small capacitor in series with one lead of a pair of sensitive high impedance headphones. I could touch two ground points like one on the engine and one on a fender and actually hear the alternator whine in the headset - no radio involved. That tells me that, at least on my vehicle, there are alternator currents flowing around the vehicle chassis and due to the resistance of the metal and connections, there is a small AC voltage between various different "ground" points.


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W8JX
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Posts: 5673




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« Reply #5 on: June 13, 2012, 11:51:13 AM »

Power line filters work well *IF* the noise is coming down the positive power lead. It won't help if the noise is entering via a "sneak" ground path caused by having multiple ground connections on the radio.

About the only thing that will try to sneak in ground path in a mobile is RFI for rig itself getting into it. I have never used a inline choke like about and not had it help problem. Kenwood actually discontinued it many years ago for a bit and then brought it back again. It is very effective.
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AA4PB
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Posts: 12793




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« Reply #6 on: June 13, 2012, 02:14:11 PM »

I've solved quite a number of noise issues by analyzing current flow through multiple ground paths in installations like audio, video, mobile radio, and instrumentation at an antenna test facility. Trust me, it doesn't take RF to have unwanted noise issues.
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W8JX
Member

Posts: 5673




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« Reply #7 on: June 13, 2012, 02:31:59 PM »

Trust me, it doesn't take RF to have unwanted noise issues.

Never said it did. Other than RFI from rig itself most mobile noise either comes up power lead that is generated by vehicle  or QRN thru antenna.
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KA3NXN
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Posts: 108


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« Reply #8 on: June 19, 2012, 03:44:05 AM »

Go to Alan's website. It' a MUST READ for any operator who will be installing equipment in their vehicle. Running the negative cable to the chassis may or may not do any good. It won't help if the chassis is also not grounded to the battery. They both have to be at the same potential. So in comes bonding. Please read the part on bonding and understand it. Don't rely on the poor bonding that is supplied by the automaker. Also, if you are mounting the antenna on the trunk or the hood, I have found like in the case of my Ford Expedition the hood is not metal, so this explains why I had a soaring SWR on my 2 meter antenna. No ground. I can't stress enough about reading Alan's website. He even has sound files that you can listen to, to identify what ignition, alternator, and various other types of mobile nose sound like. Don't waste your money on any filters.

Alan's site can be found here: http://k0bg.com/

Enjoy,

Jaime-KA3NXN
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