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Discussion in 'Discussions, Opinions & Editorials' started by AC2Q, Nov 6, 2012.

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  1. AC2Q

    AC2Q Ham Member QRZ Page

    My station is "reasonably" grounded, as in an 8'solid copper ground rod, clamped and soldered to #6 solid copper wire, 6 feet from radio, etc.

    Having some RFI issues, affecting usb devices when running legal limit.

    So, QUESTION: I have some appropriate mix toroids.

    Suppose I fold a cable in half, and wind it through the toroid, effectively then having 2 inductors in series wound in opposite directions.
    (doing this because cable ends will not fit through center of toroid.)

    While I believe this results in a net inductance close to 0, will it still serve as an effective RFI choke?

    Constructive Comments Welcomed.

  2. KE7ZOE

    KE7ZOE Ham Member QRZ Page

    No. For "legal limit", I suggest you do it right. You haven't told us what antenna, tuner, cable or bands.

    Turn off the amplifier and learn to drive your signal without line transmission, RFI and SWR.
    It seems weird that you're running "legal limit" but can't figure out how to fix RFI.

    We need more info, and you need less power.
  3. K8JD

    K8JD Ham Member QRZ Page

    Why don't you just fix your antenna system?
  4. K0RGR

    K0RGR Premium Subscriber QRZ Page

    If I understand what you're doing, I don't think it will work. The point of adding the toroid is to add inductance to block the RF.

    Fixing your antenna system sounds good, but is often easier to say than to do. I have a weird RFI issue here. On one particular antenna - a balanced dipole - I have RF in the shack on 40 and 80 meters. The antenna seems right, and is fed through a balun at the feedpoint. The coax shield is well grounded to a pair of bonded ground rods and buried radials. I'm thinking about moving the antenna again, because a length of the feedline may just be too close to one side of the antenna. I have no RFI at all when using the very unbalanced vertical in the back yard.

    For very stubborn cases, I find that the ferrite rods used to wind filament chokes for big amplifiers work much better than the garden variety toroid.
  5. NC5P

    NC5P Ham Member QRZ Page

    No it won't work. Order a split core from Amidon. You can fit any cable regardless of what's on the ends.
  6. NC5P

    NC5P Ham Member QRZ Page

    Another thought: If you have access to a water saw (wet tile saw) you can cut it in two and epoxy it back together after passing the cable through. I've done that a few times. I've also air gapped cores (for flyback converters) that way. I didn't have any trouble using that method, made a clean cut and didn't harm the blade nor the toroid.
  7. K0BG

    K0BG Platinum Subscriber QRZ Page

    There is more to grounding a station than just a ground rod. Fact is, if that's all you've done, lets hope you don't have a lightning strike. You might want to look at this:
  8. W7AKV

    W7AKV Ham Member QRZ Page

    If you dont know you experiment and learn, believe me I dont know but I can share an experience. 7 mhz was turning my tv on and off or changing settings. when I removed midi cable
    from tv no issues. so I put 50 #43 cores around a midi cable not a easy task when you have to splice a midi cable. 19 little wires but at 100 watts problem solved.
    now comes the amp 600 watts tv goes on and off. Well a day off from work and a couple of busch lights I Doug deeper.
    I made a box that spliced the power cable from tv to wall and in that box I removed the ground wire from the wall and ran a ground wire from that box to a 8' ground rod so ty still has a ground but removed from other line voltage grounds
    problem solved. not really sure if Its correct but It worked, and trying to understand It by reading things Im thinking It could have been a ground loop.
    some people understand electronics and things like this than there are heating guys like me

  9. K5FH

    K5FH Ham Member QRZ Page

    I agree with Alan. A good RF ground and a good AC ground (for 60 Hz or lightning strikes) aren't necessarily the same thing. What you describe sounds like a decent 60 Hz ground, a minimal RF ground and a terrible lightning ground. And it isn't up to the task of adequately grounding a legal limit amp if you're getting that kind of RFI.

    RF grounding is almost as much art as it is science and sometimes you just have keep trying different configurations until you get it right.

    The information on Tom, W8JI's, site is a very good place to start your search for options:
  10. N0AZZ

    N0AZZ Ham Member QRZ Page

    Alan is correct you would be much better off just using you 3 prong electrical outlets than what your doing.
  11. KB5UKT

    KB5UKT Ham Member QRZ Page

    RF is a surface animal, by this I mean it's only on the outside of the ground conductor. Copper braid or tinned copper braid (better) will work the best for a RF ground. A solid #6 wire is not bonding (RF bonding) your amp/coax/radio to ground. As others have said, DC ground is different from RF ground.
    Also the type of torroid material you use will have a big impact on the ability to attenuate the RF on the cables, some are for low frequencys and some are for high frequencys. Not much over a couple hundred MHz...
    I have seen shelded MIDI cables but they are $$$$$$. Good luck Mike KB5UKT
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