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Building a simple Alternator whine / ignition filter

Discussion in 'Home Brew' started by Moleculo, Dec 18, 2008.

  1. Whiplash-265

    Whiplash-265 Active Member

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    I'm looking to give this a try, but I'm unable to find a similar style of cap

    what i did find were a couple of differently rated ones but the wires are both on the same end and there's no flow shown on them



    both are 4700uf 25v
    one is marked 18x35 7mm CAP LYT RDL
    the second is 16x32mm CAP LYT RDL

    the arrows going down the band shown in the other pics are merely rectangles

    again i appreciate the feedback

    thanx
     

  2. K1LA

    K1LA W9WDX Amateur Radio Club Member

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    What a wonderful suggestion!
    I've got mine built and ready to throw in line but (and I realize this may sounds stupid), I just am a little confused on the best way to connect. My wiring all terminates to powerpoles and comes direct from the battery --> powerwerx in line 15amp fuse --> radio (using a T connector). I get that the red/black not on the capacitor side goes to the radio (easy enough to power pole them and throw in line) but how do I connect the other end? Just put it only on the red side of the wire and have the black side continue along ?

    my apologies for such a novice question.
     
  3. Moleculo

    Moleculo Administrator
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    The side of the electrolytic cap with the bars going down the side is the negative side.

    The capacitor side goes to the radio. If you you're using an anderson power pole on the filter connection, you need to add a run of black wire inside the filter to ground also attached to the cap. This cap in this circuit is shunting any AC noise present on the line to ground while letting the DC current pass.
     
  4. K1LA

    K1LA W9WDX Amateur Radio Club Member

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    hmmm...... could be a little late for that now that I've glued this thing in strong enough to outlast world war three. That being said, say I skip the powerpoles, would I just solder the connections in line? The radio side seems straight forward enough, red to red, black to black, but on the other side just solder the the red in line correct?

    Thanks much!
     
  5. ghilliesnpr

    ghilliesnpr Member

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    I just built one and out of curiosity decided to measure the inductance. I got 135mH but I'm sure that could vary a bit. I hope it takes care of my noise problem.

    Thanks
     
  6. Moleculo

    Moleculo Administrator
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    Solder it, use butt connectors, whatever you want. Remember, the black wire is going to need to go to ground somewhere, for both the radio and this filter.
     
  7. Beetle

    Beetle Sr. Member

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    See Post #15 for connection clarification.

    Also, for the newer guys, this filter won't work on noise coming in via the antenna. Before you invest the time making the filter, turn your radio and engine on so you're experiencing the noise.

    Then disconnect the antenna. If the noise is still there, the filter will probably help. If the noise isn't present with the antenna removed, look elsewhere for the source.
     
  8. bwharper78

    bwharper78 Member

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    I know this has been discussed, but I am still a little confused about the hookup. Right now I have power going from my battery terminals to the radio (red and black wire). Do I need to cut the red wire and put the filter inline, then ground the black filter wire to my chassis?
     
  9. Blue Jay

    Blue Jay W9WDX Amateur Radio Club Member

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    Yes that is the way to do it.
     
  10. BrianJ

    BrianJ Member

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    Another satisfied DIY customer. This filter solved my alternator noise problem.

    Thanks for the guidance!

    Brian
    N5BRJ
     
  11. slarty42

    slarty42 Member

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    "I just built one and out of curiosity decided to measure the inductance. I got 135mH but I'm sure that could vary a bit. I hope it takes care of my noise problem."

    hey ghilliesnpr are you sure thats not micro henrys or nano henrys that you measured?

    I had some round enclosed cores ( ceramic) kicking around so I wound a bobin with about 12 ft ( all I could fit inside the ceramics) of 14 gauge enameled wire & it only measures about .23 milihenrys.

    I am going to try it later today or tomorrow & see if it helps, if it does I may wind another one & make up a T filter ( my intent is to use this coil as the centre of a PI filter btw)

    So far I have found defective diodes in the alternator, had that rebuilt & its MUCH quieter but there is still an audible whine, tried several different ground points & methods with no appreciable results, it has been suggested that a new battery may help as well but this one is not showing signs of weakness

    This is all to feed a stereo head (kenwood after market) that is just being used as a preamp to drive the stock amplifiers

    Thanks for posting this project by the way, its great to see there are still hobbiests out there !

    Cheers
    Howard
     
  12. slarty42

    slarty42 Member

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    just an update, I tried making one of these as noted on a link, used the 12 ga wire etc, mine measured .046 milli henrys , also tried 2 of my small coils & made a "T" filter total of about .5 mh total, neither unit helped much with the whine but I found that when I flexed the plug on the radio upwards it made the noise come in louder & disappear depending on how much I flexed it so I replaced that plug on the adapter with the new one from the new stereo I bought & all is fine now without the filter.

    Would still like to know if I am missing something on the wound coil as my inductance values are so different to the ones stated on earlier posts

    Cheers
     
  13. oldslowchevy

    oldslowchevy Guest

    i just made this yesterday and installed it last night........ amazing. all noise is GONE. i do still have alittle noise when i use the windsheild wipers though. but i am very pleased on how this works. thank you so much for this.
     
  14. Beetle

    Beetle Sr. Member

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    If you can live with the wiper motor noise, well and good. If you'd like to try eliminating or reducing it, get some disc ceramic capacitors (value not really critical). Voltage rating AT LEAST 50 volts; most are rated around 200V so that's fine. There used to be a place near downtown in Seattle (Radar Electric) that sold mixed-value disc ceramics by the POUND! I invested five dollars for five pounds of them and I still have four pounds or so left, after using them on Navy ships for three decades or so for applications very much like this!

    I'd look for capacitance values anywhere from 0.05 μf to 0.5 μf to start. Then get access to the wiper motor itself. Check the brushes and make sure they are in good shape. They could be the cause of the problem if they're worn or the slip rings aren't messed up. Assuming slip rings/brushes are okay, add one capacitor from the hot terminal of the motor to ground. Then check to see if the noise level has gone down. If so, try adding a second capacitor in parallel with the first one.

    You might never eliminate ALL the noise, but as you reported, a lot of it is gone.
     
  15. skidrow

    skidrow Member

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    seems a long way to go around just install a better ground or bond everything...Maybe that was to easy?
     

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