Channel Master Stereo Probe 9
The Channel Master Stereo Probe 9, model number 3025 (previously 4408), is an outdoor receiving antenna for the FM broadcast band. It is a Log-Yagi array with nine elements on a 138" boom. Four elements are driven.
I modeled the antenna with the AO-Pro 7.03 Antenna Optimizer program. This image shows the antenna geometry.
This shows segmentation detail for the phasing lines and feedpoint (red dot). Blue dots indicate analysis-segment boundaries. The first phasing-line section is bowed inward to avoid the mast, while the second is mysteriously elevated and jointed, as shown below.
Modeling experiments indicate that the joint elevation has no effect on antenna performance.
Modeling Results
Below are calculated performance figures for a segmentation density of 40 segments per halfwave. Mismatch loss is due to SWR. Wire loss is due to conductor resistance. Mismatched gain is forward gain including wire and mismatch losses. F/B is the ratio of forward power to that directly to the rear. The SWR reference impedance is 300 ohms.
88.000 MHz: Impedance 127 - j141 ohms
SWR 2.98
Mismatch Loss 1.23 dB
Wire Loss 0.04 dB
Mismatched Gain 6.98 dBd
F/B 16.27 dB
90.000 MHz: Impedance 200 - j2 ohms
SWR 1.50
Mismatch Loss 0.18 dB
Wire Loss 0.03 dB
Mismatched Gain 8.49 dBd
F/B 26.39 dB
92.000 MHz: Impedance 304 + j71 ohms
SWR 1.26
Mismatch Loss 0.06 dB
Wire Loss 0.02 dB
Mismatched Gain 8.70 dBd
F/B 33.26 dB
94.000 MHz: Impedance 402 + j67 ohms
SWR 1.42
Mismatch Loss 0.13 dB
Wire Loss 0.02 dB
Mismatched Gain 8.63 dBd
F/B 28.91 dB
96.000 MHz: Impedance 441 + j5 ohms
SWR 1.47
Mismatch Loss 0.16 dB
Wire Loss 0.01 dB
Mismatched Gain 8.63 dBd
F/B 31.12 dB
98.000 MHz: Impedance 398 - j42 ohms
SWR 1.36
Mismatch Loss 0.10 dB
Wire Loss 0.01 dB
Mismatched Gain 8.77 dBd
F/B 36.91 dB
100.000 MHz: Impedance 326 - j22 ohms
SWR 1.11
Mismatch Loss 0.01 dB
Wire Loss 0.01 dB
Mismatched Gain 9.00 dBd
F/B 25.49 dB
102.000 MHz: Impedance 275 + j55 ohms
SWR 1.23
Mismatch Loss 0.05 dB
Wire Loss 0.02 dB
Mismatched Gain 9.11 dBd
F/B 19.06 dB
104.000 MHz: Impedance 274 + j168 ohms
SWR 1.80
Mismatch Loss 0.37 dB
Wire Loss 0.02 dB
Mismatched Gain 8.85 dBd
F/B 15.13 dB
106.000 MHz: Impedance 371 + j286 ohms
SWR 2.36
Mismatch Loss 0.78 dB
Wire Loss 0.02 dB
Mismatched Gain 8.29 dBd
F/B 12.89 dB
108.000 MHz: Impedance 578 + j160 ohms
SWR 2.12
Mismatch Loss 0.60 dB
Wire Loss 0.03 dB
Mismatched Gain 8.08 dBd
F/B 12.79 dB
Patterns
Antenna File
Probe 9 Free Space 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 #22 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. Disable bent-wire correction.
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Updated October 12, 2007
