Building your loop
Tuning your loop
Options for power and bandwidth
Remote tuning your loop
Safety and RF hazards
The picture shows the 1M loop tuned to the 20m band and the Icom IC-7300 inbuilt SWR meter showing SWR over a range of frequencies which is super low. You can see the basic bandwidth is a 80Khz span. Stacked loops can give more bandwidth about 30% more. Or you can put them in series for low freq operation.
Magnetic loop Antennas are very narrow band tuned via a variable capacitor in parallel this provides excellent rejection selection and high signal to noise ratio beating noisy whips and wire antennas.
Being semi directional you can null out noise or point it at the station for enhanced performance.
External links of interest:
Loop design calculator