The MFJ-1786 Mag Loop Antenna

Well, I bit the bullet today and placed my order with MFJ for an MFJ-1786 magnetic loop antenna. I have been looking at these for years, and have always been fascinated by mag loops. Magnetic loops are very efficient and are much smaller than full-size (resonant) loops.

They have the reputation of being immune to noise affecting the electric field (“static”) generated in the near field, meaning all that QRM given off by consumer electronics and power lines. They are extremely narrow in bandwidth, which is why this one comes with a dedicated tuning device. Interesting write-up on magnetic loops here.

The MFJ-1786 loop

The MFJ-1786 works anywhere between 10 and 30 MHz. That covers the 30-meter band up to the 10-meter band.  They also sell the MFJ-1788 which goes down to 40 meters, but I have read that it can have trouble tuning up down there so I am playing it safe and sticking to the higher bands.

I have never used a loop before and am very excited to get one on the air. I have heard hams use them, and invariably, they are coming in the strongest of all in the group.

MFJ Magnetic Loop Antenna

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Magnetic Loop Antenna

You can read the reviews on the MFJ-1786 on eHam reviews here.

MFJ antenna details

This 36-inch diameter loop antenna lets you operate 10 through 30 MHz continuously — including the WARC bands. It may be mounted for vertical or horizontal polarization!

Do both DX and local contacts when mounted vertically. Get both low angle radiation for excellent DX and high angle radiation for local, close-in contacts. Handles 150 Watts. Fast/Slow tune buttons and built-in two range Cross-Needle SWR/Wattmeter lets you quickly tune to your exact frequency.

All welded construction, no mechanical joints, welded butterfly capacitor with no rotating contacts, a large 1.050-inch diameter round radiator gives you the highest possible efficiency. Each plate in the tuning capacitor is welded for low loss and polished to prevent high voltage arcing, welded to the radiator, has nylon bearing, anti-backlash mechanism, limit switches, continuous no-step DC motor — gives smooth precision tuning. Heavy-duty thick ABS plastic housing has ultraviolet inhibitor protection.

Here is the radiation pattern of a horizontally-mounted Super Hi-Q Magnetic Loop Antenna.
radiation
Magnetic loop

The radiation pattern of a small loop antenna is essentially omnidirectional with the exception of two very narrow nulls in the axis of the loop. If you visualize the loop as a “wheel”, the nulls are in the same directions that the “wheel’s axle” would run.

Signals will be attenuated more than 10 dB if they arrive within 15 degrees of the axis of the loop.

11 thoughts on “The MFJ-1786 Mag Loop Antenna”

  1. I’m very interested to find out how the loop is preforming for you. I was going to get one but was holding off as they are not cheap. I would have to put mine in the attic.
    Mike
    VE3WDM

    Reply
  2. Hi Mike-
    The loop performs as well as I had hoped. I have worked stations easily as far as eastern Europe, southern Africa, even with the loop only 6 feet off the ground. I'd say it performs as well as a dipole 1 wavelength up.

    I am moving soon, so the shack is decommissioned now, but I will have more reports up next spring.

    Reply
  3. I have not mounted it properly with the included hardware yet (I am in the process of moving QTH).

    I just hung it on a tree branch up about 7 feet, and it worked very well!

    Reply

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