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Thread: high noise floor, is it my OCF dipole?

  1. #1
    normd's Avatar
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    Default high noise floor, is it my OCF dipole?

    I have been having problems with a high noise floor for over 10 years, in fact it was why i gave up radio 5 years ago. I now live at a new QTH, my kids have left home and all of the tv's and other electronics in the house have been replaced over the last 5 years apart from the microwave but the problem remains s5-s7 static noise on 40-17m 12 & 10 are clear with only one common factor my OCF Dipole. my set up is the OCF dipole with 4:1 balun at the feed point mounted as inverted V 30 ft at the center and approximately 8ft and 15ft at the ends. this is fed with 10m rg213-U to the bottom of the mast and into a 1:1 rf current balun/choke, from there is another 15m rg213-U to the shack.

    I have always used this type of dipole because of it's ability to tune 40-10m and have never tried single band dipole's and wondered if anyone on this forum has had similar experiences and found a solution maybe a balanced dipole or vertical.

    couple of things I have tried,

    Turning off the power so only the radio is on, but not powered with battery as this will not be easy but can try if necessary
    unplugging the coax to make sure the noise is coming from the antenna.

    This is the antenna https://www.m0cvoantennas.com/apps/w...s/show/7856277

    This is the rf choke https://www.m0cvoantennas.com/apps/w...s/show/2628660
    Norman - 2EFAS

  2. #2

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    Hi normd,

    I also have a high noise floor on both 80 & 40m. I solved it by getting a noise canceler. I got the kit QRM-180 kit from AG6YJ on eBay -- it is a kit that I built and so far it has been amazing on what it has eliminated.

    Now every case is different, but for the ~$80 and a few days of kit building, it could be something to try. There are other noise canceling units out there that are not kits that you could also try, but I know from experience that this one can reduce the noise.

    Just another option to consider ...

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    I wonder if the isolator has DC ground. Maybe Ohm it to check. If so, make sure it has a resonable ground.

    I have become a fan of 1:1 baluns in general specifically for this feature. Draining off static buildup often help with wire antennas ... in small sampling.
    -Jeff NE1U

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    normd's Avatar
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    Quote Originally Posted by Psi* View Post
    I wonder if the isolator has DC ground. Maybe Ohm it to check. If so, make sure it has a resonable ground.

    I have become a fan of 1:1 baluns in general specifically for this feature. Draining off static buildup often help with wire antennas ... in small sampling.
    Don't think it has an earth just an so239 at each end how would you go about adding one?
    Norman - 2EFAS

  5. #5
    normd's Avatar
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    Quote Originally Posted by Psi* View Post
    I wonder if the isolator has DC ground. Maybe Ohm it to check. If so, make sure it has a resonable ground.

    I have become a fan of 1:1 baluns in general specifically for this feature. Draining off static buildup often help with wire antennas ... in small sampling.
    I have looked at noise cancelling like the MFJ 1026 but they are expensive and can only cancel noise from one source so it could work as a last resort.
    Norman - 2EFAS

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    Not to state the obvious, but you never know: Are you using your RF gain at all?

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    Try engaging the attenuator. It's normal for 40 & 80 to have a high noise floor.

  8. #8
    Super Moderator 2E0FVL's Avatar
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    Normd, What you got is what we all have at the moment while we are in the sunspot low.
    Stick with it you just got to get a lucky day, I did last Thurs filled my boots first time in months using Data modes & SSB.
    I have a FT450D and an 40 Mtr OCD Dipole ONLY 15ft over ground.
    Pete - 2EFVL
    The QRM Formally Known As M6PAP!!
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  9. #9
    normd's Avatar
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    Thanks for all the advice guys tbh I didn't know it was usual on 40 although I also have it on 30 & 20 as well but the attenuator does work. I have an ft450d as well so it's nice to know it isn't my setup and we're all in the same boat. Here's to my lucky day :-)
    Norman - 2EFAS

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