The following is an adapted article originally penned by AB6SL

2E0ERO Magnetic Loop Antenna

The 2E0ERO MagLoop is very well made, as well as being surprisingly small and lightweight - easy to mount or transport and it's a lot of fun to use. It's great for attenuating locally-generated QRM. It has a maximum power handling of 30W, well suited to the 25W limitation of the Foundation Licence.

Not documented in most reviews of this magnetic loop or any other magnetic loop, commercial or homebuilt, is the fact that the radiation lobes are very wide - aligned with the plane of the vertically oriented loop. You often hear that vertically oriented loops have a donut-shaped radiation pattern, sending energy in a 180-degree arc - which is great for NVIS, but not so much for DX. Orienting the loop horizontally, gives you an omnidirectional pattern, but with more energy having the desired, low angles of incidence for DX. 

If your QTH suffers a lot of locally-generated QRM, you'll be much better off using the loop in a vertical orientation, tuning it for lowest SWR at the desired target frequency, THEN rotating the loop to null out the noise, as best as possible. The nulls are perpendicular to the plane of the loop, but they "feel/sound" narrower than the lobes of the radiation pattern. If you're lucky, having rotated the loop to lower the noise floor, the transmit lobes will still provide enough energy at the ideal azimuth to work the station you're hearing extremely well. LOL

This is why, at least for noisy locations, I see the 2E0ERO being a GREAT antenna for receiving. Out in the woods (or at any low-noise location), its 30W maximum RF output, could best be used for transmitting, by rotating the loop to maximize the signal received from a station you want to work - or try a horizontal orientation for an omnidirectional, low angle of incidence. Loops are also great as NVIS antennas, when oriented vertically.

2E0ERO 17-40m MagLoop Tuning Cheat Sheet:

NOTE: The FAST button on the 2E0ERO Controller spins the capacitor 360 degrees in 17 seconds.

The SLOW button on the 2E0ERO Controller spins the capacitor 360 degrees in 29 seconds.

The SLOW button is still too fast, and thus, way too twitchy - requiring very light, short-duration AND short-stroke tapping, for a momentary contact switch that has a very long stroke before bottoming out. This demands a ridiculous amount of finesse, as it's very easy to overshoot the lowest SWR positions, requiring repeated reversals of the motor’s direction, using the controller’s toggle switch, then trying again. There's also a bit of play in the direct drive motor, requiring a slightly longer duration tap, immediately following reversal of direction, than was required prior to reversal.

TUNING THE 2E0ERO 17m to 40m MAGLOOP

1) Ensure the following settings have been specified in the radio:

a) HF MAX POWER = 30W, in Operation Setting -> TX General
b) AM MAX POWER = 5W, in Operation Setting -> TX General
This is a personal preference, so that I can easily select Mode AM (to get a 5W constant carrier on PTT), whenever checking SWR with the MagLoop (or any external impedance matching "tuner.")
The radio's internal tuner will always reduce the power level to 5W when it is Tuning, but an operator must proactively reduce output power manually, when "tuning" with any external device.
c) RF Gain at maximum.
d) AGC turned Off.
e) DNR turned Off.
f) Level adjusted to display just a little bit of noise (with a spectrum scope waterfall display, which is preferable for tuning, to using a 3DSS waterfall display).
g) Optional: IPO set to AMP1 or AMP2, when the ambient noise level is very low (or the equivalent if not using FT-710).

2) Select a rocker switch position on the MagLoop that will service the band you want to work - for 20m, either position of the rocker switch will work - as it overlaps for 20m.
a) "0" for 40m through 17m (YMMV, but 20m and 17m will tune to a lower SWR with the switch at "0" rather than "1".)
b) "1" for 20m through 10m (YMMV, but I only use the switch set at "1" for 15m, 12m and 10m.)
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3) Tune your transceiver to the frequency you want to work.
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4) Select a low power output (i.e. 5W) and constant carrier mode (i.e. AM/FM/RTTY) for tuning, as you'll be wanting to check SWR without having to modulate the carrier.
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5) Set the spectrum scope display SPAN to maximum width (i.e. 1000kHz), increase the waterfall Speed to FAST2 or FAST3, and select EXPAND to maximize the height of the spectrum scope waterfall (on the Yaesu FT-710, for example).
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6) Adjust the display Level and you might already see the noisiest chunk of the band - off to one side or the other of your center frequency. (Not easy to find with 15m, in my experience.)
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7) Watch the spectrum display as you begin by long-pressing the 2E0ERO controller’s FAST button until you see and hear the highest noise portion of the spectrum move past your target frequency, then reverse direction, using the controller's toggle switch, and fine-tune for highest noise at the target frequency, still watching the spectrum display, with short, shallow strokes of the SLOW button (reversing direction as necessary).
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8) When, through visual and auditory observation, you believe the noise to be maximized at the target frequency, check the SWR by transmitting briefly at 5W in your selected constant carrier mode (i.e. AM Mode). Make additional, short and shallow taps of the SLOW button, if necessary, to achieve the lowest possible SWR, confirming each adjustment with repeated transmissions at 5W in AM Mode, for example. You will likely overshoot the lowest SWR, more than once. LOL

Your mileage may vary, but here are the lowest SWRs I've been able to achieve, using only the 2E0ERO controller on each of the bands it supports:

40m 1.0:1 SWR at 7.175 MHz
30m 1.0:1 SWR at 10.125 MHz
20m 1.7:1 SWR at 14.225 MHz
17m 1.9:1 SWR at 18.115 MHz

9) Use the transceiver's internal tuner (or an external tuner placed at the transceiver) ONLY if your best effort with the 2E0ERO Controller has yielded an SWR higher than 1.2:1 but less than 3.0:1. In other words, the Controller can easily achieve 3.0:1 or better and 1.2:1 is good enough to warrant avoiding the use of a matching device at the transceiver.

Sidebar: Keep in mind that matching any antenna's impedance to 50 Ohms using a transceiver's built-in tuner or an external tuner that is NOT at the antenna's feedpoint, will reduce radiated RF power due to losses incurred in any type of coax cable, between the tuner and the feedpoint, due to multiple reflections and re-reflections of standing waves at any SWR greater than the ideal 1.0:1, in proportion to any increase in SWR, any increase in coax length and any increase in frequency. Each reflection and re-reflection suffer the same loss per foot, as a given type of coax induces with the original transmitted energy. The higher the SWR at the antenna feedpoint, the greater the loss of radiated RF. Thus, it's best to achieve the lowest SWR possible, using only the 2E0ERO controller, before trying to improve the impedance match at the transceiver. As an aside: All antennas should be matched to 50-Ohms at the feedpoint, when using coax. A 450-Ohm twisted ladder line, used with a 9:1 balun right before entering the shack, offers 81x less loss per foot than RG8 coax, for example, allowing use of in-shack impedance matching devices (automatic or manual tuners) without suffering the losses had when using them with coax feedlines.
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10) Do not modify the MagLoop's tuning while working this frequency. (Duh!)
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11) NOW rotate the vertically oriented MagLoop to null out locally-generated QRM. This should be in the 2E0ERO instruction sheet (along with a lot of other stuff.) The nulls are narrower than the relatively wide radiation lobes that extend in the plane of the loop, so there's not as much benefit to be had by rotating the MagLoop to yield the strongest signal from a DX station, UNLESS your location is NOT suffering from any significant amount of locally-generated QRM. The ability to greatly attenuate QRM by rotation of the loop AFTER tuning it for lowest SWR, is easily appreciated.
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12) Return to your desired mode, but transmit no more than 30W into the 2E0ERO MagLoop - per its included, single-page instruction sheet.
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13) Adjust other transceiver settings as needed, while working the tuned frequency.