The Channel Master Stereo Probe 9, model number 3025 (previously 4408), is a Log-Yagi array with nine elements on a 138″ boom. Four folded dipole elements are driven.
I modeled the antenna with the AO 9.50 Antenna Optimizer program. This image shows the antenna geometry. Unlike other designs with multiple driven elements, the Probe 9 avoids inducing current in the boom by eliminating phasing-line crossover.
This shows segmentation detail for the phasing lines. Blue dots indicate analysis segments. The red dot is the feedpoint. The phasing line is bowed inward to avoid the mast.
Ken Wetzel uses this Probe 9 at Ridgecrest, California.
Calculated performance figures are for 50 analysis segments per halfwave. 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
88 126 - j142 3.00 1.25 0.04 6.97 16.27
89 159 - j65 2.01 0.52 0.03 8.00 17.68
90 201 - j3 1.49 0.17 0.03 8.50 17.86
91 252 + j41 1.26 0.06 0.02 8.68 18.03
92 307 + j67 1.25 0.05 0.02 8.70 18.23
93 360 + j72 1.33 0.09 0.02 8.67 18.46
94 406 + j59 1.41 0.13 0.02 8.63 18.74
95 434 + j30 1.46 0.15 0.01 8.61 19.07
96 440 - j4 1.47 0.16 0.01 8.63 19.48
97 425 - j34 1.43 0.14 0.01 8.69 19.99
98 394 - j49 1.36 0.10 0.01 8.78 20.63
99 356 - j46 1.25 0.05 0.01 8.89 21.34
100 320 - j25 1.11 0.01 0.01 9.01 22.14
101 291 + j10 1.05 0.00 0.01 9.10 21.39
102 273 + j56 1.24 0.05 0.02 9.12 18.79
103 266 + j111 1.50 0.18 0.02 9.03 16.64
104 277 + j172 1.81 0.38 0.02 8.83 14.92
105 312 + j236 2.13 0.60 0.02 8.55 13.62
106 385 + j288 2.35 0.77 0.02 8.26 12.77
107 507 + j277 2.36 0.78 0.02 8.08 12.44
108 575 + j118 2.03 0.53 0.03 8.09 12.92
Probe 9 Free Space Symmetric 98 MHz 77 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 overall length a2 = a1 - 1 ; start of end curve a3 = a1 - 3 ; end of 0.5"-diameter tubing b1 = 31.75 ; DE2 b2 = b1 - 1 b3 = b1 - 3 c1 = 34.25 ; DE3 c2 = c1 - 1 c3 = c1 - 3 d1 = 37.25 ; DE4 d2 = d1 - 1 d3 = d1 - 3 d = .375 ; element diameter c = .5 ; folded dipole end diameter m = 1.75 ; director mounting bracket halfwidth b = 1 ; equivalent diameter of mounting brackets s = 1.125 ; phasing-line spacing t = .375 ; phasing-line spacing near mast h = 1.25 ; folded dipole halfheight j = h + .5 ; rise at adjustable phasing-line joint between DE2 & DE3 shift x -67.5 1 p1 -d1 0 p1 -d2 h c 1 p1 -d2 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 d2 h c 1 p1 d2 h p1 d1 0 c 1 p1 -d1 0 p1 -d2 -h c 1 p1 -d2 -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 d2 -h c 1 p1 d2 -h p1 d1 0 c 1 p2 -c1 0 p2 -c2 h c 1 p2 -c2 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 c2 h c 1 p2 c2 h p2 c1 0 c 1 p2 -c1 0 p2 -c2 -h c 1 p2 -c2 -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 c2 -h c 1 p2 c2 -h p2 c1 0 c 1 p3 -b1 0 p3 -b2 h c 1 p3 -b2 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 b2 h c 1 p3 b2 h p3 b1 0 c 1 p3 -b1 0 p3 -b2 -h c 1 p3 -b2 -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 b2 -h c 1 p3 b2 -h p3 b1 0 c 1 p4 -a1 0 p4 -a2 h c 1 p4 -a2 h p4 -a3 h c 1 p4 -a3 h p4 -s h d 1 p4 -s h p4f -s h .5 ; equiv diam = half the plate width 1 p4f -s h p4f s h #18 copper ; feedpoint 1 p4 s h p4f s h .5 ; equiv diam = half the plate width 1 p4 s h p4 a3 h d 1 p4 a3 h p4 a2 h c 1 p4 a2 h p4 a1 0 c 1 p4 -a1 0 p4 -a2 -h c 1 p4 -a2 -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 a2 -h c 1 p4 a2 -h p4 a1 0 c 1 p4 s -h p34 t -h d 1 p34 t -h p3 s -h d 1 p4 -s -h p34 -t -h d 1 p34 -t -h p3 -s -h d 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 1 p2 s -h p1 s -h .25 1 p2 -s -h p1 -s -h .25 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 42, center Mounting bracket equivalent diameter calculated with the YO 7.66 Yagi Optimizer.
88–108 MHz