The Channel Master Stereo Probe 9, model number 3025 (previously 4408), is a log-Yagi array with nine elements on a 135″ boom. Four folded dipole elements are driven.
I modeled the antenna with the AO 9.67 Antenna Optimizer program. This image shows the antenna geometry. Unlike designs with multiple driven dipoles, the Probe 9 obtains phase inversion without crossing the phasing lines. This prevents pickup of signals from the boom due to proximity imbalance.
This shows segmentation detail for the phasing lines. Blue dots indicate analysis segments. The red dot is the feedpoint. One phasing line bows inward to avoid the mast.
Ken Wetzel uses this Probe 9 at Ridgecrest, California. Model pulses that cut across corner segments at the folded dipole tips approximate the tubing curve.
Calculated performance is for 32 analysis segments per conductor halfwave with additional segments for the pinched phasing line. Forward gain includes mismatch and conductor losses. F/R is the ratio of forward power to that of the worst backlobe in the rear half-plane.
Frequency Impedance SWR Mismatch Conductor Forward F/R
MHz ohms Loss dB Loss dB Gain dBd dB
88 144-j78 2.26 0.70 0.04 7.66 17.48
89 180-j8 1.67 0.28 0.03 8.30 17.71
90 225+j46 1.40 0.12 0.03 8.55 17.90
91 275+j83 1.35 0.10 0.02 8.60 18.06
92 327+j104 1.41 0.13 0.02 8.57 18.23
93 377+j98 1.44 0.15 0.02 8.53 18.40
94 416+j83 1.49 0.17 0.01 8.50 18.70
95 440+j58 1.51 0.19 0.01 8.50 19.09
96 446+j27 1.50 0.18 0.01 8.53 19.54
97 433+j1 1.44 0.15 0.01 8.60 20.03
98 406-j13 1.36 0.10 0.01 8.70 20.65
99 373-j10 1.25 0.05 0.01 8.82 21.43
100 339+j9 1.13 0.02 0.01 8.93 22.21
101 312+j41 1.15 0.02 0.01 9.02 22.94
102 292+j86 1.34 0.09 0.01 9.03 19.82
103 286+j140 1.61 0.24 0.02 8.94 17.44
104 295+j201 1.94 0.47 0.02 8.73 15.52
105 328+j266 2.29 0.73 0.02 8.44 14.10
106 397+j323 2.57 0.93 0.02 8.14 13.09
107 515+j333 2.64 0.98 0.02 7.94 12.55
108 621+j209 2.36 0.78 0.03 7.95 12.70
Probe 9 Free Space Symmetric 98 MHz 69 6063-T832 wires, inches p1 = 0 ; element positions p2 = 20 p23 = 30 p3 = 40 p34 = 50 p4 = 60 p4f = 61.375 ; feedpoint p5 = 75 p6 = 90 p7 = 105 p8 = 120 p9 = 135 a1 = 27.25 ; DE1 half-length a3 = a1 - 3 ; start of 0.5" tip b1 = 31.75 ; DE2 b3 = b1 - 3 c1 = 34.25 ; DE3 c3 = c1 - 3 d1 = 37.25 ; DE4 d3 = d1 - 3 d = .375 ; tubing diameter c = .5 ; tubing diameter at folded dipole tips m = 1.75 ; director mounting plate half-length b = 1 ; equivalent diameter of 1.5" x 0.125" mounting plate s = 1.125 ; phasing-line half-spacing t = .375 ; half-spacing near mast h = 1.25 ; folded dipole half-height j = h + .5 ; rise at phasing-line joint between DE2 & DE3 1 p1 -d1 h p1 -d3 h c 1 p1 -d3 h p1 -2 h d 1 p1 -2 h p1 2 h b 1 p1 2 h p1 d3 h d 1 p1 d3 h p1 d1 h c 1 p1 -d1 -h p1 -d3 -h c 1 p1 -d3 -h p1 -s -h d 1 p1 s -h p1 d3 -h d 1 p1 d3 -h p1 d1 -h c 1 p1 d1 -h p1 d1 h c 1 p1 -d1 -h p1 -d1 h c 1 p2 -c1 h p2 -c3 h c 1 p2 -c3 h p2 -s h d 1 p2 s h p2 c3 h d 1 p2 c3 h p2 c1 h c 1 p2 -c1 -h p2 -c3 -h c 1 p2 -c3 -h p2 -s -h d 1 p2 s -h p2 c3 -h d 1 p2 c3 -h p2 c1 -h c 1 p2 c1 -h p2 c1 h c 1 p2 -c1 -h p2 -c1 h c 1 p3 -b1 h p3 -b3 h c 1 p3 -b3 h p3 -s h d 1 p3 s h p3 b3 h d 1 p3 b3 h p3 b1 h c 1 p3 -b1 -h p3 -b3 -h c 1 p3 -b3 -h p3 -s -h d 1 p3 s -h p3 b3 -h d 1 p3 b3 -h p3 b1 -h c 1 p3 b1 -h p3 b1 h c 1 p3 -b1 -h p3 -b1 h c 1 p4 -a1 h p4 -a3 h c 1 p4 -a3 h p4 -s h d 1 p4 -s h p4f -s h .5 ; equiv diam = half of plate width 1 p4f -s h p4f s h #18 copper ; feedpoint 1 p4 s h p4f s h .5 ; equiv diam = half of plate width 1 p4 s h p4 a3 h d 1 p4 a3 h p4 a1 h c 1 p4 -a1 -h p4 -a3 -h c 1 p4 -a3 -h p4 -s -h d 1 p4 s -h p4 a3 -h d 1 p4 a3 -h p4 a1 -h c 1 p4 -a1 -h p4 -a1 h c 1 p4 a1 -h p4 a1 h c 1 p2 s -h p1 s -h .25 1 p2 -s -h p1 -s -h .25 1 p3 s h p23 s j d 1 p23 s j p2 s h d 1 p3 -s h p23 -s j d 1 p23 -s j p2 -s h d 9 p4 s -h p34 t -h d 9 p34 t -h p3 s -h d 9 p4 -s -h p34 -t -h d 9 p34 -t -h p3 -s -h d 1 p5 -25 0 p5 -m 0 d 1 p5 -m 0 p5 m 0 b 1 p5 m 0 p5 25 0 d 1 p6 -24.5 0 p6 -m 0 d 1 p6 -m 0 p6 m 0 b 1 p6 m 0 p6 24.5 0 d 1 p7 -24.5 0 p7 -m 0 d 1 p7 -m 0 p7 m 0 b 1 p7 m 0 p7 24.5 0 d 1 p8 -24.5 0 p8 -m 0 d 1 p8 -m 0 p8 m 0 b 1 p8 m 0 p8 24.5 0 d 1 p9 -24 0 p9 -m 0 d 1 p9 -m 0 p9 m 0 b 1 p9 m 0 p9 24 0 d 1 source Wire 35, center
88–108 MHz