Osun EMF detector

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by N1QWI, Dec 12, 2020.

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  1. N1QWI

    N1QWI Ham Member QRZ Page

    Hi everyone,

    Some of you might have recalled a previous thread where I was using something called an “EMF hunter“ to detect stray RF in the shack. At the time, I was using an end fed antenna and was finding that when I put the detector around my CW key or mic, I got the detector alarm going off if I was about 1 inch from either accessory. Basically, only my hand was being exposed according to the detector. Interestingly, the detector did not yield any results of EMF with the dummy load attached.

    As you will see from the photo attached, the detector picks up both magnetic and electric fields. It specifically picked up magnetic field measured in mG but not electric field (mW/cm2) when I transmitted from my antenna.

    As an experiment, I put up an 80 m loop antenna and was curious to see what would happen with my detector. Interestingly, I had almost the same kind of results just like with my end-fed. Actually-I think the loop antenna yielded more stray RF fields on 1-2 more bands compared to the end fed, despite the fact that the loop tunes up better on most bands. Both antennas tune up very well on many bands with my MAT-30 tuner.

    The loop antenna has a 4:1 BalUn using coax feed line in about 120 feet to my house.
    As of right now, I do not have anything (including transmitter chassis) grounded so I wonder if this is the solution?

    I am also attaching a picture of this “EMF hunter“

    Curious what you all think!
    Daniel N1QWI

    Attached Files:

  2. K6CLS

    K6CLS Ham Member QRZ Page

    SWR has nothing to do with RFI. Well, not much anyway.
    N1QWI and K0UO like this.
  3. W6MK

    W6MK Ham Member QRZ Page

    1. The "EMF hunter" gizmo is pure scam. Take it apart and look at what the circuit amounts to.
    You, as a licensed "Extra" should be able to think this kind of stuff through. A SW radio of any quality
    is a far superior electromagnetic energy detecting device. I use an inexpensive portable SW radio
    to scan for RF interference in my house and my neighborhood environment. I won't explain this further.

    2. End fed antenna systems are notorious for bringing common-mode RF into the shack. That's what's
    going on with your key and mic. This can be limited with the use of a high-quality common mode choke.

    3. A dummy load is perfectly matched to the short transmission line connecting it to your TX. The RF is
    contained in the differential current flow in the center coax conductor and the inside of the braid.
    No common mode current.

    4. RF energy is electromagnetic energy. There is no separation of magnetic and electric fields.
    KD0CAC likes this.

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