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home-brew noise filter

Discussion in 'General CB Services Discussion' started by BOOTY MONSTER, Feb 25, 2009.

  1. BOOTY MONSTER

    BOOTY MONSTER
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    had to get new plugs and wires for my truck and now im getting noise . i used good plugs (autolite double platnums) and good wires (autolite pro-fit) that should be more than adaquate for my old truck . anyhow im looking at this home made noise filter .......
    San Antonio Hams
    and he says its good for 20 amps . was wondering if anyone knows and cares to share how to build one to handle 50 amps or more ???



    thanks .
     

  2. mackmobile43

    mackmobile43
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    would this work with larger cable? http://www.worldwidedx.com/home-bre...-simple-alternator-whine-ignition-filter.html
     
  3. Beetle

    Beetle
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    Probably would. Try it and see what happens.
     
  4. Moleculo

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    Yeah, just use a little larger cable if you really need 50amps. It might be easier to make it around a large bolt with bigger cable, though
     
  5. dudmuck

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    That home-brew filter is good for noise which is conducted via your DC power wires.

    But are you sure its conducted? because maybe its radiated instead.

    The only way to know is to disconnect your antenna from the radio.
    If its still there, then its conducted and the DC filter can help.

    But if your noise is radiated, then the antenna is picking it up.
    Noise blankers on radios work to a limited extent.
    But better to reduce the noise at the source.
    For ignition noise, make sure the engine block has a good braided strap grounding to vehicle chassis. Grounding the engine hood, tailpipe, and even the radiator can help. Sometimes ferrite beads on the high-voltage ignition wires can help.

    Alternator whine is a different issue entirely. Its a conducted noise. Often the whine is indicative of a ground loop, or in otherwords: DC power not being drawn directly from battery.
     
  6. Dodgem250

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    The best home made noise suppressor filter I have ever constructed is a basic simple design, small transformer and a 1000uf Cap. Mount in side of the radio inline with the radios power wire, adds a great deal of suppression to the line noise.
     
  7. C2

    C2
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    Would that be a 1:1 isolation transformer, and which side would tha cap go to?
     
  8. Beetle

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    Transformers don't work well as transformers at DC. If you were to use just one of the windings and short the other one(s), it might work to block the AC portion, which is the noise.
     
  9. Hambone

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    The home brew filter worked great for me. No more whine and no more ignition noise. great post.
     
  10. HomerBB

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    I used this same filter on my SUV. It did wonders for the noise levels in my radio. There is a little residual noise from time to time that could be helped I'm thinking with a more serious grounding of the body to frame etc.

    I recommend it.(y)
     
  11. Onthecoast

    Onthecoast
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    Im going to try and make one of these today to see how it works. Lots of other commercial filters that do the same thing are $70, and this one seems pretty straight forward and inexpensive. Anyone else had any luck with this in the last few years since it was posted. I know this works for alternator whine, I am interested to see if it will do anything for other electrical noise that I am seeing from electric fans.
     
  12. Onthecoast

    Onthecoast
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    Made one today with the wire I had on hand, but I don't know if I will use it. The voltage drop across the filter is too much. On full draw (20a) I'm seeing ~13.5 V to my power block right before the filter and 12.6 at the end of the filter. I don't know a ton about voltage drop, but I'm not comfortable with that right now. I will have to redo with some larger gauge wire for my current radio or use it with a lower power radio.
     

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