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Author Topic: Alternator whine.  (Read 19340 times)
KG6YSF
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Posts: 91




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« on: September 21, 2013, 07:23:38 PM »

Okay so I have been reading everything I can find on the subject and as this takes into effect three different categories I decided to poste it here. I have a CB and a FT-2900 in my Jeep. I had to upgrade to a Powermaster 140 amp alternator and dual Optimas because of the 10,000 pound winch, 20 lights under the vehicle for night time wheeling, Viair on-board dual air compressor system. I also have 6 work lights for night time breakdowns. The compressors draw 18 amps each and they are needed for the axle lockers. They cycle the whole time I am offroad. I can't use a smaller alternator or batteries. The winch can pull 500 amps at full load. Now I have wicked alternator whine on both the CB and ham while the engine runs it makes it difficult to communicate on the go. I have been told to use ferrite beads on both the power and ground wires for each device. The thing is I have also been told that that is a bandaide not a fix. My power cables for the ham are 10g and both go strait to the battery. The cb is only 4w output and so it has 12g power and ground again to the battery. I have extra ground straps between the body and the frame as well as the engine block and the frame and the engine block and the body. the radios are mounted to a overhead console that I made up out of square tube for the frame and aluminum diamond plate. It is mounted to the role bar and windshield frame.
So now what? I am ready to try anything at this point. Huh
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"Rangers Lead The Way!"  "Sua Sponte"   "Litalis Velox Silens"
When all else fails ham radio is there!
FT2900, FT8900, VX6, Ft60, TS940SAT, Drake TR7, MFJ 969
KA4POL
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Posts: 2125




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« Reply #1 on: September 21, 2013, 09:39:57 PM »

About thirty years ago my cure in a similar case was a 10,000 µF capacitor close to the radio DC input. 4700 µF might do as well. The voltage rating should be about 25 V or better.
I rather do not comment on the description  Grin
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VA7CPC
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« Reply #2 on: September 21, 2013, 10:20:53 PM »

On my boat, I put a _large_ split ferrite on the output lead of the alternator, at the alternator terminal.  That reduced the alternator hash considerably.  It may be a Band-aid, but it'll help stop the bleeding.

.              Charles
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M6GOM
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« Reply #3 on: September 22, 2013, 03:22:17 AM »

What you've not told us is how the antennas are mounted and if there's any ground straps on the radios.
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W8JX
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Posts: 6671




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« Reply #4 on: September 22, 2013, 05:21:23 AM »

Okay so I have been reading everything I can find on the subject and as this takes into effect three different categories I decided to poste it here. I have a CB and a FT-2900 in my Jeep. I had to upgrade to a Powermaster 140 amp alternator and dual Optimas because of the 10,000 pound winch, 20 lights under the vehicle for night time wheeling, Viair on-board dual air compressor system. I also have 6 work lights for night time breakdowns. The compressors draw 18 amps each and they are needed for the axle lockers. They cycle the whole time I am offroad. I can't use a smaller alternator or batteries. The winch can pull 500 amps at full load. Now I have wicked alternator whine on both the CB and ham while the engine runs it makes it difficult to communicate on the go. I have been told to use ferrite beads on both the power and ground wires for each device. The thing is I have also been told that that is a bandaide not a fix. My power cables for the ham are 10g and both go strait to the battery. The cb is only 4w output and so it has 12g power and ground again to the battery. I have extra ground straps between the body and the frame as well as the engine block and the frame and the engine block and the body. the radios are mounted to a overhead console that I made up out of square tube for the frame and aluminum diamond plate. It is mounted to the role bar and windshield frame.
So now what? I am ready to try anything at this point. Huh

I would not worry about a bigger alternator. Stock one is around 120 and 20 amps will not make a difference but dual batteries will big time. No need to do optimas either save your money. I have plowed snow commercially for over 20 years. It is far harder on batteries than than your usage. I use dual stock batteries and alternator and have a good battery service life of several years. (I change them every 3 or 4 years regardless of their condition) The key is dual batteries not a bigger alternator. With stock alternator a replacement is cheaper when needed. Also a bigger alt can overload stock wiring and fuse link. On whine, you can do as above but you could have a bad diode in alt too.
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You can embrace new computer/tablet technology and change with it or cling to old fall far behind....
WX7G
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« Reply #5 on: September 22, 2013, 07:52:13 AM »

A quick check before proceeding: Disconnect the antenna coaxial cable from the CB radio or the FT-2900. Is the alternator whine still there? The answer will drive the fix.

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K5LXP
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« Reply #6 on: September 22, 2013, 08:11:47 AM »


Ferrites work at RF, not AF frequencies.  "Whine" falls in the AF frequency range.

First thing I would do is check the alternator for a bad diode.  An alternator can have a bad diode and still pass a current output test so the way to do this is with an oscilloscope.  A normal alternator will have a little bit of ripple but one with a bad diode will have a periodic spike or valley which can cause the noise you're experiencing.

This document shows an example of this:

www.pvv.org/~syljua/merc/TooSeptST07.pdf

The other thing that can cause alternator whine in a radio is a ground loop.  This is usually because either the alternator, the battery or the radio has a (relatively) high impedance power path to chassis ground.  You stated that you ran the power wires for the radios straight to the battery but there very well could be a missing or bad ground from the engine to the frame or from the battery to the frame.  WX7G's comment would reveal one possible path for a ground loop, through the coax shield.  Ground loops are the more common cause of whine in equipment and can range from just annoying whine to melted wiring and fried radios.

You can build or buy alternator whine filters for stereos and 2-way equipment that consist of a series inductor and shunt capacitor but those should only be considered when you've ruled out the fault conditions above.  If it's not a bad alternator, it almost surely is a ground loop problem so don't band-aid it with a filter.  With all the modifications, gadgets and accessories you've got wired into this vehicle I'm going to bet you've got a ground loop.

Mark K5LXP
Albuquerque, NM
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AA4HA
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Posts: 1640




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« Reply #7 on: September 22, 2013, 10:03:23 AM »

Another way to find out if there is a bad diode is to use a DVM across the alternator but put it on the AC volts scale. This works best with a peak-hold DVM. You should not see anything more than a few millivolts of AC noise on the alternator output.

You can test the effectiveness of the filtering capacitors by monitoring the AC volts on the DC output. The greater the capacitance the lower the value will be of the AC noise/ripple.

If you have a bad diode the only solution will be to 1) replace the diode or 2) replace the alternator.

Depending upon how the diode failed you can also be exposing your vehicle electrical system to high voltage spikes. A vehicle alternator is really a three phase AC generator with diodes to rectify that to DC. High voltage spikes is a great way to blow out your engine control module (ECM) that can cost up to a thousand dollars.

We used really large alternators on vehicles like ambulances because there was a constant load from the lights and the gear in back. In those cases we would sometimes put a 200 amp alternator in a vehicle. For vehicles exposed to intermittent load (like a winch) more battery capacity (peak currents) was the best choice.
« Last Edit: September 22, 2013, 10:06:12 AM by AA4HA » Logged

Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
KG6YSF
Member

Posts: 91




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« Reply #8 on: September 22, 2013, 11:48:47 AM »

What you've not told us is how the antennas are mounted and if there's any ground straps on the radios.

No ground straps to the radios as they are for reality they are mounted to the frame via the roll bar and windshield frame. CB antenna is on a ball mount on the back of the body. the ham antenna is mag mount middle of the hood until I can get a Firestik 2m on a ball mount that will be on the back of the body as well. need ruged antenna systems due to vehicle abuse.
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"Rangers Lead The Way!"  "Sua Sponte"   "Litalis Velox Silens"
When all else fails ham radio is there!
FT2900, FT8900, VX6, Ft60, TS940SAT, Drake TR7, MFJ 969
KG6YSF
Member

Posts: 91




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« Reply #9 on: September 22, 2013, 11:49:53 AM »

A quick check before proceeding: Disconnect the antenna coaxial cable from the CB radio or the FT-2900. Is the alternator whine still there? The answer will drive the fix.



Thanks for this will try it this afternoon.
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"Rangers Lead The Way!"  "Sua Sponte"   "Litalis Velox Silens"
When all else fails ham radio is there!
FT2900, FT8900, VX6, Ft60, TS940SAT, Drake TR7, MFJ 969
KG6YSF
Member

Posts: 91




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« Reply #10 on: September 22, 2013, 12:08:05 PM »

High output alternator is already there as are dual yellow top Optimas. That is not being changed as winching when on your side and fuel not getting to the pick up to feed the injectors has and does happen. When winching with the engine not running I need the batteries. I am also happy to have too much alternator than not enough, as I will be adding an on-board welder soon.
As stated earlier I have many ground straps from battery to frame, frame to body, body to battery.
I do not have or know anyone who does have an o-scope.
Will post a pic of the mounted radios for visual clarification if I knew how.

 
« Last Edit: September 22, 2013, 12:12:14 PM by KG6YSF » Logged

"Rangers Lead The Way!"  "Sua Sponte"   "Litalis Velox Silens"
When all else fails ham radio is there!
FT2900, FT8900, VX6, Ft60, TS940SAT, Drake TR7, MFJ 969
AA4PB
Member

Posts: 13032




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« Reply #11 on: September 22, 2013, 12:22:52 PM »

When you disconnect the antenna, if the noise goes away then touch the coax shield to the antenna ground connection to see if it returns. If it does that is an indication that you have a ground loop via the antenna ground. If it doesn't then it means that the noise is being picked up by the antenna (which is not likely with alternator whine).

Next try setting the radio on the seat to make sure it has only one ground connection (the cable to the battery) and see if you still have the whine. If its quiet on the seat and noisy in the mount that shows that you have a ground loop issue.
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W8JX
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Posts: 6671




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« Reply #12 on: September 22, 2013, 12:30:45 PM »

Extra batter power is good to have. Once  I had a apt fail in a plow truck in predawn hours and was able to finish and limp home on dual batteries. I would suggest you add a small portable 800 to 1000 watt 2 stroke generator and 35 amp charger to your war chest. No oil to spill out of crankcase and a way to recharge batteries of road if you need to winch a lot and cannot run engine. Also consider replacing some lighting with LED's where possible as is frees up power for other uses. I replaced all running lights and brake lights with leds's is a plow truck and cut power draw over 12 amps. Free power.
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You can embrace new computer/tablet technology and change with it or cling to old fall far behind....
K5LXP
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Posts: 4536


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« Reply #13 on: September 22, 2013, 03:13:54 PM »

I have many ground straps from battery to frame, frame to body, body to battery.

What about engine to frame?  Engine, transmission and exhaust mounts are great at isolating vibration and electric current.  The engine to frame path carries as much current as the alternator "hot" lead.  Sometimes you'll see this as a negative lead from the battery to the starter frame but not always.  There is usually a common ground point where both the battery and the engine will  be connected to the chassis. 

Quote
I do not have or know anyone who does have an o-scope.

It could save you a lot of time chasing ghosts in your ground system.  Does not need to be a fancy scope.

Mark K5LXP
Albuquerque, NM

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KG6YSF
Member

Posts: 91




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« Reply #14 on: September 22, 2013, 09:13:21 PM »

Didn't get to mess with it today. Life happened. Angry A tree went down across the road and since it is private road we have to take care of that kind of thing our selves. Since there are people that live further up the valley so it isn't something that just effects me. As well there is only one way in and out of the valley. It may be a few days now so I can let my back relax a bit. I'll let you know, and thanks every one for your input.
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"Rangers Lead The Way!"  "Sua Sponte"   "Litalis Velox Silens"
When all else fails ham radio is there!
FT2900, FT8900, VX6, Ft60, TS940SAT, Drake TR7, MFJ 969
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