Larger multi-turn loops with the turns too close together can be degraded by the "proximity effect": the turn in the front (or in the case of a spiral, the outermost turn) may have a certain current value at a given point on that turn; but the turn adjacent to it next to that point may have a current that is quite different. This can cause (among other things) increased current in a given area. You can spread the turns out to reduce this effect, but the bottom line is that losses can be much higher than in single-turn loops.

Here's what Owen Duffy states:

Small Transmitting Loops (STL) are loops of less than about 0.1λ in diameter or about 0.3λ in circumference. Below these limits, the current around the loop is almost uniform and this permits a simplified analysis.

According to this, the total length of the conductor in a multiturn loop should be less than about 0.3λ depending on how close the turns are to each other.

IIRC, the two-turn loop in the 11/11 QST actually had significantly more loss than the single-turn one. Here are the files.

Larger multi-turn loops with the turns too close together can be degraded by the "proximity effect": the turn in the front (or in the case of a spiral, the outermost turn) may have a certain current value at a given point on that turn; but the turn adjacent to it next to that point may have a current that is quite different. This can cause (among other things) increased current in a given area. You can spread the turns out to reduce this effect, but the bottom line is that losses can be much higher than in single-turn loops.

Here's what Owen Duffy states:

Small Transmitting Loops (STL) are loops of less than about 0.1λ in diameter or about 0.3λ in circumference. Below these limits, the current around the loop is almost uniform and this permits a simplified analysis.

According to this, the total length of the conductor in a multiturn loop should be less than about 0.3λ depending on how close the turns are to each other.

IIRC, the two-turn loop in the 11/11 QST actually had significantly more loss than the single-turn one. Here are the files.

Multi-turn loops with the turns too close together have the "proximity effect" issue. The turn in the front (or in the case of a spiral, the outermost turn) may have a certain current value at a given point on that turn; but the turn adjacent to it next to that point may have a current that is quite different. This causes (among other things) increased current in a given area. You can spread the turns out to reduce this effect, but the bottom line is that losses can be much higher than in single-turn loops.

IIRC, the two-turn loop in the 11/11 QST actually had significantly more loss than the single-turn one. Here are the files.

Larger multi-turn loops with the turns too close together can be degraded by the "proximity effect": the turn in the front (or in the case of a spiral, the outermost turn) may have a certain current value at a given point on that turn; but the turn adjacent to it next to that point may have a current that is quite different. This can cause (among other things) increased current in a given area. You can spread the turns out to reduce this effect, but the bottom line is that losses can be much higher than in single-turn loops.

Here's what Owen Duffy states:

Small Transmitting Loops (STL) are loops of less than about 0.1λ in diameter or about 0.3λ in circumference. Below these limits, the current around the loop is almost uniform and this permits a simplified analysis.

According to this, the total length of the conductor in a multiturn loop should be less than about 0.3λ depending on how close the turns are to each other.

IIRC, the two-turn loop in the 11/11 QST actually had significantly more loss than the single-turn one. Here are the files.