Channel Master Stereo Probe 9

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.

Modeling Results

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

Antenna File

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

July 12, 201888108 MHz