It is known that the most valuable piece of the magnetic loop antenna is a capacitor, which must be able to handle very high voltage in case of 30+ watts of emitting power (up to 5000V for 100 watts).
The construction of the Magnetic Loop antenna is pretty simple: the one or two loops of wire (the more diameter of the wire is better) and capacitor breaking the loop. But in case of making the loop using the coaxial cable, there is an ability to retire the capacitor. The reason is simple: coaxial cable has its own capacitance. Therefore if you know the linear capacitance of your coax you can calculate the required length of the cable which creates the resonant contour on the desired frequency. Below is a sketch of the coax wiring allowing you to use both the cable shield and the linear capacitance of the coax (the image source).
The construction of the Magnetic Loop antenna is pretty simple: the one or two loops of wire (the more diameter of the wire is better) and capacitor breaking the loop. But in case of making the loop using the coaxial cable, there is an ability to retire the capacitor. The reason is simple: coaxial cable has its own capacitance. Therefore if you know the linear capacitance of your coax you can calculate the required length of the cable which creates the resonant contour on the desired frequency. Below is a sketch of the coax wiring allowing you to use both the cable shield and the linear capacitance of the coax (the image source).
Next is a picture of two antennas made using this approach. People reports pretty good results when using inside the room and driving only 5 watts (Yaesu FT-817).
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