Alternator whine

[Thayne]

I am having problems with alternator whine coming thru a 2096 I installed in my sisters' Subaru WRX. I fed it from the existing feed for the stock radio, and got the ground from an exposed metal framing member bolt behind the radio.
(The stock radio has no noise problems)

The noise is present even when the volume is all the way down, so I'm assuming it isn't radiated, but coming in on the power. Is it better to try to filter it at the alternator or the radio?
I have seen capacitors mounted right at the alternator, but also someone told me that sometimes a bad diode in the alternator can cause a whine.

Any advice?

 

[pinetree]

The noise is fed by your hot wire into the radio. This is an old fix which I have used many times. Using a speaker transformer such as Radio Shack 273-1380 connect the output ( the wires which would go to the speaker) in series with the feed wire going to the radio. Then tape the other wires from the transformer. This acts like a choke coil and will block the AC whine from the alternator. I would not mess with the alternator It could void the car warranty. Need help send me a message

 

[Thayne]

It sounds like that would work, but mounting it would be problematic--not anywhere good between the fuseblock and the radio.

I appreciate the feedback

 

[RocketMan1]

Are you getting the whine through your car stereo as well? If so, make sure the alternator is/has a good ground.

 

[Thayne]

Not coming thru the stereo, even tho its fed from the same fuse. Maybe the 2096 has bad filtering of the power lead.
I have put in about 10 of them, and only had a problem with this Subaru

 

[iMONITOR]

What are you using for an antenna? Is it mounted outside the vehicle, and properly grounded?

 

[Thayne]

NMO on roof, antennex gain ant. I'm sure its not coming thru the front end, as reception is great, you can hear the whine even when the volume is all the way down, and it doesn't get louder when the volume is up--

 

[pinetree]

Try the transformer first. It should mount on the back of the radio with velcro. For a few bucks you will know for sure.

 

[Thayne]

I have lots of them around in old radios, etc. I will hook one up temp and see what happens. I'm not taking that radio out again; too much hassle with too much Subaru plastic.

 

[popnokick]

Thayne- By your description, it is definitely alternator whine coming in on the power lead, and NOT via the antenna. A simple way to confirm this is to disconnect the antenna and see if the noise is still there. If it is, you have alternator whine coming in via the 12v lead. Alternator whine also usually varies in pitch with engine speed.

You need to use a filter on the power lead. The most effective are the ones that use both a capacitor and choke coil (inductor) to "smooth out" the DC power and remove the AC waveform introduced by the alternator. A choke (transformer) or capacitor alone are usually not enough to do the trick. You can build your own, but fortunately there are several good ones commercially available for $10-$30, depending on the current (amps) your radio draws. A 10 amp filter is going to be more than adequate... scanner receivers don't draw anywhere near that power (transmitters are a different story). Here are links to several that incorporate both a coil and one or more capacitors:

http://cbworldinformer.com/200108/magnum_power_filter.htm

http://www.calrad.com/calrad/95series.shtml [scroll down to Item 95-867A]

http://www.partsexpress.com/pe/showdetl.cfm?Partnumber=265-030

Radio Shack, NAPA, and other auto parts stores have them, too. Don't get confused: Look specifically for "alternator whine filter". There are many other "noise filters" for other types of noise. You need one specifically for alternator whine.

 

[Thayne]

Thanks everyone. I am going to haywire one together and temp it in, (I have a lot of parts around), if it works I will buy one like that last link has.
I need it to be easy to install near the fuse block.

I scoped the power thru a cap and there is definately some ripple on the DC.

 

[ke5lvt]

i have found the power filter made by kenwood to be the best. i dont recall the part number right now. i looked at this one (http://www.partsexpress.com/pe/showdetl.cfm?Partnumber=265-030) it seems to be simler. hope 1 of these will fix it for you.

 

[firescannerbob]

I've got the same problem...need suggestons

I've read this thread on alternator whine, and I have a similar problem. The previous suggestions however, won't help, so I need some other suggestions.
I have Tao XM radio, that works on either a 12v cig lighter adapter or an internal battery. It's fed to my car stereo via the stereos aux input.
When I'm listening to the XM, I get some pretty serious alternator whine. I first thought that it was the cable that goes from the XM's line out to the stereos aux input, but I ruled that out. If
I plug my MP3 player into the same cable, there is no whine. There is also no whine when listening to FM radio, or CD's.
After a little more experimentation, I found that the ONLY time I get alternator whine is when the XM is powered via the cig lighter adapter. If I unplug the adapter (and operate the XM with it's battery) the whine goes away. Obviously the cig lighter adapter is picking up the whine.
I'm thinking that I can crack open the adapters case, and add some filtering of some type, but don't know what to add.
Any suggestions on how to cure this wold be greatly appreciated!

 

[kc2kvz]

You might also try a ferrite bead on the power wire. For a couple bucks, it's worth a try.

 

[FC73]

Noise Problem

I, too, am having a noise problem. I have a Pro-75 that picks up engine noise in my van. Also a Pro-528 that I bought as a Christmas present picks up this noise. Since these are both handhelds and running on battery the solutions posted so far will not work. What else can be done? I am assuming that the noise I am getting is the alternator whine spoken of here. The faster the engine goes the pitch of the noise gets higher and the noise gets faster. I don't know but perhaps that is the nature of the beast when using handhelds inside an automobile.
Any info would be appreciated
FC73

 

[Thayne]

If it sounds like a motorboat, it's not the alternator--it's ignition noise.

 

[iMONITOR]

A car's own computer module can be a big source of noise too! Not sure what they sound like, but I've heard the HAM's on 2-meter talking about certain manufactures are worse than others.

 

[FC73]

Ignition noise

The noise I have is a fast popping noise, faster as the engine goes faster. If that is ignition noise what can be done for it?
FC73

 

[firescannerbob]

As for my problem, I dug around my miscellaneous "junk" drawer and found a USB cable (I have no idea what it was for) that had a snap-on ferrite choke. I snapped it around the XM adapters power cable, and sure enough the alternator whine is 99% less. Thanks for the suggestion.
While I was researching this, I found a listing for an OEM car adapter for my XM, and the photo shows that the newer models have a choke built-in to the cable. Appears that it must be a common problem with this model.

 

[Thayne]

Check your plug wires, if they are old or if you are using solid core wires when resistance wires are stock that will do it. If the antenna is close to the engine it will make it worse, Freqs lower than 50MHZ are more susceptible, as are AM receivers