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CM 3D multi-turn loop
CM qrp.gaijin@yahoo.com (2014/04)
CE
SY C=5.85e-12
SY r=6e-3
SY s=5
GW 17 3 -2.22e-16 1 3.6 -2.22e-16 1 3.75 r
GW 18 5 0 1 3.75 0 0 3.75 r
GW 19 3 0 0 3.75 0 0 3.6 r
GW 20 s 0 0 3.6 0.45 0.03571429 3.15 r
GW 21 s 0.45 0.03571429 3.15 5.5511e-17 0.07142857 2.7 r
GW 22 s 5.5107e-17 0.07142857 2.7 -0.45 0.10714286 3.15 r
GW 23 s -0.45 0.10714286 3.15 -1.11e-16 0.14285714 3.6 r
GW 24 s -1.102e-16 0.14285714 3.6 0.45 0.17857143 3.15 r
GW 25 s 0.45 0.17857143 3.15 5.5511e-17 0.21428571 2.7 r
GW 26 s 5.5107e-17 0.21428571 2.7 -0.45 0.25 3.15 r
GW 27 s -0.45 0.25 3.15 -1.11e-16 0.28571429 3.6 r
GW 28 s -1.102e-16 0.28571429 3.6 0.45 0.32142857 3.15 r
GW 29 s 0.45 0.32142857 3.15 5.5511e-17 0.35714286 2.7 r
GW 30 s 5.5107e-17 0.35714286 2.7 -0.45 0.39285714 3.15 r
GW 31 s -0.45 0.39285714 3.15 -1.11e-16 0.42857143 3.6 r
GW 32 s -1.102e-16 0.42857143 3.6 0.45 0.46428571 3.15 r
GW 33 s 0.45 0.46428571 3.15 5.5511e-17 0.5 2.7 r
GW 34 s 5.5107e-17 0.5 2.7 -0.45 0.53571429 3.15 r
GW 35 s -0.45 0.53571429 3.15 -1.11e-16 0.57142857 3.6 r
GW 36 s -1.102e-16 0.57142857 3.6 0.45 0.60714286 3.15 r
GW 37 s 0.45 0.60714286 3.15 5.5511e-17 0.64285714 2.7 r
GW 38 s 5.5107e-17 0.64285714 2.7 -0.45 0.67857143 3.15 r
GW 39 s -0.45 0.67857143 3.15 -1.11e-16 0.71428571 3.6 r
GW 40 s -1.102e-16 0.71428571 3.6 0.45 0.75 3.15 r
GW 41 s 0.45 0.75 3.15 5.5511e-17 0.78571429 2.7 r
GW 42 s 5.5107e-17 0.78571429 2.7 -0.45 0.82142857 3.15 r
GW 43 s -0.45 0.82142857 3.15 -1.11e-16 0.85714286 3.6 r
GW 44 s -1.102e-16 0.85714286 3.6 0.45 0.89285714 3.15 r
GW 45 s 0.45 0.89285714 3.15 5.5511e-17 0.92857143 2.7 r
GW 46 s 5.5107e-17 0.92857143 2.7 -0.45 0.96428571 3.15 r
GW 47 s -0.45 0.96428571 3.15 -1.11e-16 1 3.6 r
GE -1
LD 5 17 0 0 58000000
LD 5 18 0 0 58000000
LD 5 19 0 0 58000000
LD 0 18 3 3 0 0 C
LD 5 20 0 0 58000000
LD 5 21 0 0 58000000
LD 5 22 0 0 58000000
LD 5 23 0 0 58000000
LD 5 24 0 0 58000000
LD 5 25 0 0 58000000
LD 5 26 0 0 58000000
LD 5 27 0 0 58000000
LD 5 28 0 0 58000000
LD 5 29 0 0 58000000
LD 5 30 0 0 58000000
LD 5 31 0 0 58000000
LD 5 32 0 0 58000000
LD 5 33 0 0 58000000
LD 5 34 0 0 58000000
LD 5 35 0 0 58000000
LD 5 36 0 0 58000000
LD 5 37 0 0 58000000
LD 5 38 0 0 58000000
LD 5 39 0 0 58000000
LD 5 40 0 0 58000000
LD 5 41 0 0 58000000
LD 5 42 0 0 58000000
LD 5 43 0 0 58000000
LD 5 44 0 0 58000000
LD 5 45 0 0 58000000
LD 5 46 0 0 58000000
LD 5 47 0 0 58000000
GN 2 0 0 0 3 0.0004
EK
EX 0 18 3 0 0 0 0
FR 0 0 0 0 7 0
EN
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The simulation results are as shown in the following image.
Addendum 2015-01-03
From the above current diagram (where blue represents lower current flow and red represents higher current flow) it is clear that there is little current flowing in the horizontal section of the antenna connecting the two loop ends. This horizontal section of the antenna contains the loop resonating capacitance of 6 pF. Therefore, there is very little current flowing through the resonating capacitor. This is because the multi-turn loop structure is almost self-resonant by itself with no capacitor.
It follows that by adjusting the turn spacing or diameter, the structure can be made self-resonant with no need for an additional resonating capacitor.
Then, the proper term for this kind of a long, multi-turn, self-resonant radiator is a "normal mode helix". Here is an article describing practical construction and matching of a normal-mode helix for VHF use: w6nbc.com/articles/2011-06QST2mhelices.pdf .
Though I yet haven't built one, I see nothing that would prevent a similar antenna from being built for HF use.
