MFJ amplified receiving loop antenna testing

Discussion in 'Amateur Radio News' started by KJ4YZI, May 17, 2017.

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  1. KJ4YZI

    KJ4YZI Ham Member QRZ Page

    So i finally got around to checking this thing out. A powered receive loop that covers 500khz to 30mhz, and has the same characteristics as their magnetic loop antenna, but no tuning required. Not designed for transmitting, however if you have an HF radio capable of transmitting on antenna A and receiving on antenna B, then you can open up your ears and null out the noise. You can see in this video how it eliminates the high level of interference from power and gives more received signal.
     

    Attached Files:

    N3DAW and IX1FIT like this.
  2. KE0EYJ

    KE0EYJ Ham Member QRZ Page

    OP... nice video. You answered some questions of mine on 100w and a wire on FB, today.

    I want to ask others on this .... how would this stack up against a simple, non-amped flag receive antenna? Any guesses?

    I'd like to buy one of these, but shipping here, to Korea, would likely be pretty bad, as they are in a big box. Have been thinking of building and trying a simple flag antenna out, as soon as I can get around to finding the torrid, and resistor I need, here in Seoul.
     
  3. KE0EYJ

    KE0EYJ Ham Member QRZ Page

  4. KC2SIZ

    KC2SIZ Ham Member QRZ Page

    Thanks for this. I personally would rather have a passive, tuned loop even if it's just for listening, but that's just me.
     
  5. AF6LJ

    AF6LJ Premium Subscriber QRZ Page

    The loop I use gives me anywhere from 2-4 S units in noise reduction and an S-Unit increase in signal over my doublet, depending on how it is orientated to the primary noise source.
     
    DL1ATZ and KK5JY like this.
  6. KE0EYJ

    KE0EYJ Ham Member QRZ Page

    What loop do you use?
     
    AF6LJ likes this.
  7. AF6LJ

    AF6LJ Premium Subscriber QRZ Page

  8. KK5JY

    KK5JY Ham Member QRZ Page

    I like the passive untuned loops [kk5jy.net], particularly on the lower bands. As long as the loop is large enough to set the noise floor in the receiver, the S/N can be even better than with a tuned loop. That's what the MFJ and DXE loops are, essentially, an untuned loop with a preamp. I just like to omit the preamp whenever possible to avoid the noise figure of the preamp.

    That said, I'm also amazed that people tolerate power line noise, especially when it's obvious which pole is the problem. Before dropping a few hundred $$$ on an antenna, get them to fix the power pole. After all, you are paying the power provider to do maintenance, through the check you send them every month. They won't proactively search for noise, you have to find it and report it.

    Once the power line noise is gone, you can really evaluate the difference between a vertical and a receiving loop. :cool:
     
  9. AF6LJ

    AF6LJ Premium Subscriber QRZ Page

    That is easier said than done to get the power company to deal with the problem.
     
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  10. KK5JY

    KK5JY Ham Member QRZ Page

    I agree. It took me 18 months, two visits from Mike Martin, and an FCC letter to the utility to get them to even admit they had a problem. However, once they got to that point, they became very good at resolving power line noise issues. If I can get them to the pole (an Arrow V/UHF antenna is your best friend when hunting power line noise), they can usually get it fixed in a day or two. So it's not difficult once they are motivated.

    One thing is for sure, if you don't address the problem, it will never go away, and it will never get better.
     
    Last edited: May 18, 2017
    AF6LJ likes this.

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