Joe,
This is what I was trying to project at the meeting regarding the wealth of information on repeater-builder.com which offers this free old DOS DB products software to calculate the azimuthal pattern for a side-mounted antenna and I'm glad that despite the vitriolic display to me by Don, he saw fit to quantify the azimuthal pattern with this software. For those members who may be interested, the software is near the bottom of the page at http://www.repeater-builder.com/antenna/ant-sys-index.html
"Look for DB Products Side-Mount"
Now since you asked what I think....
I remain a bit skeptical about this software because it appears to give similar results for different tower "face dimensions" which I understood from the tower crew was 16 feet and not 5 feet as entered for the resulting graph of equal field lines, you forwarded to me. This leads me to speculate that Don knows that the upper tower face section is 5 feet. (Is it?) Additionally, if you enter "0" for the "antenna offset" parameter in the software it will plot ½ foot increment deepest null information too.
Also, the concentric doted circles are at 5db/div which is OK but gives the appearance of a subtle change and when changing the tower face dimension to say 16 feet on the software, the graph shows a small change in the pattern. - Thus my skepticism for this particular software.
However, I have worked out a spreadsheet comparison between a 4 ft and 6 ft offset, at 1 degree increments, with the same 5 ft tower face parameter. The results show a mild but discernable improvement in the "overall performance" and the club may want to opt for the 6 ft offset if we have to pay for a 4 ft offset bracket anyway. I haven't checked but I suspect that it would benefit the 220Mhz antenna performance too.
This software does not address the vertical pattern which I am also concerned about, but we may not be able to do much about this with our current budget limited hardware....
The original graph file forwarded to me was left off of this email because I didn't know if the ETS club's email address would support its transmission....
In a personal note, I have clearly been left out of the loop by certain members of the "towerizer crew" (Nicknamed by Drew) which is an issue that I will address later.....
Spreadsheet Calculations showing the difference follows:
These numbers show the db level comparison at each degree and the bottom "merit number" shows "overall" more gain from the 6 ft offset antenna.
What say? OMs 73 Hank N2MU ...-.- ..
146.94
MHz
Difference Between
4 ft and 6ft offset
Direction
db reference
db reference
Positive = 6ft offset better
degree
4 ft from tower
6 ft from tower
Negative= 4 ft offset better
North
0
7.5
5.62
1.88
1
7.7
5.89
1.81
2
7.9
6.15
1.75
3
8.09
6.42
1.67
4
8.27
6.68
1.59
5
8.44
6.94
1.50
6
8.6
7.19
1.41
7
8.75
7.44
1.31
8
8.89
7.69
1.20
9
9.02
7.93
1.09
10
9.14
8.15
0.99
11
9.24
8.37
0.87
12
9.33
8.58
0.75
13
9.41
8.78
0.63
14
9.47
8.96
0.51
15
9.52
9.13
0.39
16
9.55
9.29
0.26
17
9.57
9.42
0.15
18
9.57
9.54
0.03
19
9.55
9.64
-0.09
20
9.52
9.72
-0.20
21
9.47
9.78
-0.31
22
9.41
9.82
-0.41
23
9.34
9.84
-0.50
24
9.25
9.84
-0.59
25
9.15
9.81
-0.66
26
9.03
9.77
-0.74
27
8.9
9.7
-0.80
28
8.76
9.62
-0.86
29
8.61
9.51
-0.90
30
8.45
9.38
-0.93
31
8.29
9.24
-0.95
32
8.11
9.08
-0.97
33
7.93
8.91
-0.98
34
7.74
8.73
-0.99
35
7.55
8.53
-0.98
36
7.35
8.32
-0.97
37
7.16
8.1
-0.94
38
6.96
7.87
-0.91
39
6.75
7.64
-0.89
40
6.55
7.4
-0.85
41
6.35
7.16
-0.81
42
6.15
6.92
-0.77
43
5.95
6.67
-0.72
44
5.75
6.43
-0.68
45
5.56
6.19
-0.63
46
5.37
5.94
-0.57
47
5.19
5.71
-0.52
48
5.01
5.47
-0.46
49
4.84
5.24
-0.40
50
4.67
5.02
-0.35
51
4.51
4.81
-0.30
52
4.36
4.6
-0.24
53
4.21
4.4
-0.19
54
4.08
4.21
-0.13
55
3.95
4.02
-0.07
56
3.83
3.85
-0.02
57
3.72
3.69
0.03
58
3.62
3.54
0.08
59
3.53
3.41
0.12
60
3.45
3.28
0.17
61
3.38
3.17
0.21
62
3.32
3.07
0.25
63
3.28
2.98
0.30
64
3.24
2.91
0.33
65
3.22
2.85
0.37
66
3.21
2.81
0.40
67
3.21
2.79
0.42
68
3.23
2.77
0.46
69
3.26
2.78
0.48
70
3.3
2.8
0.50
71
3.35
2.84
0.51
72
3.42
2.89
0.53
73
3.5
2.97
0.53
74
3.6
3.06
0.54
75
3.71
3.17
0.54
76
3.83
3.29
0.54
77
3.97
3.44
0.53
78
4.13
3.6
0.53
79
4.29
3.78
0.51
80
4.48
3.98
0.50
81
4.67
4.2
0.47
82
4.89
4.44
0.45
83
5.11
4.7
0.41
84
5.35
4.98
0.37
85
5.61
5.27
0.34
86
5.88
5.29
0.59
87
6.16
4.72
1.44
88
6.45
4.19
2.26
89
6.02
3.7
2.32
East
90
5.49
3.25
2.24
91
4.99
2.83
2.16
92
4.53
2.44
2.09
93
4.09
2.08
2.01
94
3.68
1.76
1.92
95
3.3
1.46
1.84
96
2.95
1.19
1.76
97
2.62
0.95
1.67
98
2.31
0.74
1.57
99
2.02
0.55
1.47
100
1.76
0.39
1.37
101
1.51
0.26
1.25
102
1.29
0.16
1.13
103
1.08
0.08
1.00
104
0.9
0.03
0.87
105
0.73
0
0.73
106
0.58
0
0.58
107
0.45
0.03
0.42
108
0.34
0.08
0.26
109
0.24
0.16
0.08
110
0.16
0.27
-0.11
111
0.1
0.4
-0.30
112
0.05
0.57
-0.52
113
0.02
0.76
-0.74
114
0
0.99
-0.99
115
0
1.24
-1.24
116
0.01
1.53
-1.52
117
0.04
1.85
-1.81
118
0.08
2.21
-2.13
119
0.14
2.6
-2.46
120
0.21
3.04
-2.83
121
0.3
3.52
-3.22
122
0.4
4.04
-3.64
123
0.51
4.62
-4.11
124
0.64
5.25
-4.61
125
0.78
5.95
-5.17
126
0.93
6.72
-5.79
127
1.1
7.41
-6.31
128
1.28
7.21
-5.93
129
1.48
7.02
-5.54
130
1.69
6.86
-5.17
131
1.91
6.72
-4.81
132
2.15
6.59
-4.44
133
2.4
6.49
-4.09
134
2.66
6.41
-3.75
135
2.94
6.35
-3.41
136
3.23
6.31
-3.08
137
3.54
6.09
-2.55
138
3.86
5.47
-1.61
139
4.2
4.92
-0.72
140
4.55
4.42
0.13
141
4.92
3.97
0.95
142
5.31
3.56
1.75
143
5.17
3.19
1.98
144
5.04
2.86
2.18
145
4.92
2.56
2.36
146
4.81
2.28
2.53
147
4.72
2.04
2.68
148
4.63
1.82
2.81
149
4.56
1.62
2.94
150
4.49
1.44
3.05
151
4.44
1.29
3.15
152
4.39
1.15
3.24
153
4.35
1.03
3.32
154
4.33
0.93
3.40
155
4.31
0.84
3.47
156
4.3
0.77
3.53
157
4.3
0.71
3.59
158
4.3
0.67
3.63
159
4.32
0.64
3.68
160
4.34
0.61
3.73
161
4.37
0.6
3.77
162
4.4
0.6
3.80
163
4.44
0.61
3.83
164
4.49
0.63
3.86
165
4.54
0.66
3.88
166
4.6
0.69
3.91
167
4.66
0.73
3.93
168
4.73
0.78
3.95
169
4.8
0.83
3.97
170
4.88
0.89
3.99
171
4.96
0.96
4.00
172
5.05
1.03
4.02
173
4.97
1.1
3.87
174
4.79
1.18
3.61
175
4.62
1.26
3.36
176
4.45
1.34
3.11
177
4.3
1.42
2.88
178
4.15
1.51
2.64
179
4.01
1.6
2.41
South
180
3.88
1.69
2.19
181
3.76
1.78
1.98
182
3.65
1.87
1.78
183
3.54
1.96
1.58
184
3.44
2.05
1.39
185
3.35
2.13
1.22
186
3.26
2.22
1.04
187
3.18
2.3
0.88
188
3.1
2.38
0.72
189
3.03
2.46
0.57
190
2.97
2.53
0.44
191
2.91
2.6
0.31
192
2.86
2.66
0.20
193
2.81
2.72
0.09
194
2.77
2.78
-0.01
195
2.73
2.83
-0.10
196
2.7
2.87
-0.17
197
2.68
2.91
-0.23
198
2.66
2.94
-0.28
199
2.64
2.96
-0.32
200
2.64
2.98
-0.34
201
2.64
2.99
-0.35
202
2.64
2.99
-0.35
203
2.65
2.99
-0.34
204
2.67
2.98
-0.31
205
2.7
2.96
-0.26
206
2.73
2.94
-0.21
207
2.77
2.91
-0.14
208
2.81
2.87
-0.06
209
2.87
2.83
0.04
210
2.93
2.78
0.15
211
3
2.73
0.27
212
3.08
2.67
0.41
213
3.16
2.61
0.55
214
3.26
2.54
0.72
215
3.37
2.47
0.90
216
3.48
2.39
1.09
217
3.61
2.32
1.29
218
3.75
2.24
1.51
219
3.9
2.15
1.75
220
4.06
2.07
1.99
221
4.24
1.99
2.25
222
4.43
1.9
2.53
223
4.63
1.82
2.81
224
4.85
1.74
3.11
225
5.09
1.66
3.43
226
5.34
1.58
3.76
227
5.61
1.5
4.11
228
5.89
1.43
4.46
229
6.2
1.37
4.83
230
6.53
1.3
5.23
231
6.67
1.25
5.42
232
6.39
1.2
5.19
233
6.12
1.16
4.96
234
5.86
1.12
4.74
235
5.61
1.09
4.52
236
5.36
1.07
4.29
237
5.12
1.06
4.06
238
4.9
1.06
3.84
239
4.68
1.07
3.61
240
4.48
1.09
3.39
241
4.28
1.12
3.16
242
4.1
1.17
2.93
243
3.92
1.22
2.70
244
3.76
1.29
2.47
245
3.61
1.37
2.24
246
3.48
1.47
2.01
247
3.35
1.58
1.77
248
3.24
1.71
1.53
249
3.15
1.85
1.30
250
3.06
2.01
1.05
251
3
2.18
0.82
252
2.95
2.37
0.58
253
2.91
2.58
0.33
254
2.89
2.81
0.08
255
2.89
3.05
-0.16
256
2.91
3.32
-0.41
257
2.94
3.6
-0.66
258
2.99
3.9
-0.91
259
3.07
4.23
-1.16
260
3.16
3.92
-0.76
261
3.27
3.53
-0.26
262
3.41
3.15
0.26
263
3.57
2.8
0.77
264
3.76
2.47
1.29
265
3.97
2.16
1.81
266
4.21
1.87
2.34
267
4.48
1.61
2.87
268
4.66
1.37
3.29
269
4.71
1.16
3.55
West
270
4.78
0.97
3.81
271
4.86
0.8
4.06
272
4.96
0.65
4.31
273
5.08
0.53
4.55
274
5.21
0.43
4.78
275
5.37
0.36
5.01
276
5.53
0.31
5.22
277
5.72
0.29
5.43
278
5.91
0.29
5.62
279
6.13
0.32
5.81
280
6.36
0.38
5.98
281
6.6
0.46
6.14
282
6.85
0.57
6.28
283
7.12
0.71
6.41
284
7.4
0.88
6.52
285
7.21
1.09
6.12
286
6.56
1.32
5.24
287
5.96
1.59
4.37
288
5.41
1.89
3.52
289
4.9
2.24
2.66
290
4.42
2.62
1.80
291
3.98
3.05
0.93
292
3.58
3.52
0.06
293
3.2
4.05
-0.85
294
2.85
4.64
-1.79
295
2.53
5.28
-2.75
296
2.23
6.01
-3.78
297
1.95
6.81
-4.86
298
1.7
7.71
-6.01
299
1.47
8.73
-7.26
300
1.26
9.9
-8.64
301
1.06
10.13
-9.07
302
0.89
9.87
-8.98
303
0.73
9.63
-8.90
304
0.59
8.79
-8.20
305
0.47
7.79
-7.32
306
0.36
6.91
-6.55
307
0.27
6.13
-5.86
308
0.19
5.44
-5.25
309
0.13
4.81
-4.68
310
0.08
4.25
-4.17
311
0.04
3.75
-3.71
312
0.02
3.29
-3.27
313
0.01
2.88
-2.87
314
0.01
2.52
-2.51
315
0.02
2.18
-2.16
316
0.04
1.89
-1.85
317
0.07
1.62
-1.55
318
0.12
1.39
-1.27
319
0.17
1.18
-1.01
320
0.23
1
-0.77
321
0.31
0.84
-0.53
322
0.39
0.71
-0.32
323
0.48
0.59
-0.11
324
0.58
0.5
0.08
325
0.69
0.43
0.26
326
0.8
0.38
0.42
327
0.93
0.34
0.59
328
1.06
0.33
0.73
329
1.2
0.32
0.88
330
1.34
0.34
1.00
331
1.5
0.37
1.13
332
1.66
0.41
1.25
333
1.82
0.47
1.35
334
1.99
0.54
1.45
335
2.17
0.62
1.55
336
2.35
0.72
1.63
337
2.54
0.83
1.71
338
2.73
0.94
1.79
339
2.93
1.07
1.86
340
3.13
1.22
1.91
341
3.33
1.37
1.96
342
3.54
1.53
2.01
343
3.75
1.7
2.05
344
3.97
1.88
2.09
345
4.19
2.06
2.13
346
4.41
2.26
2.15
347
4.63
2.46
2.17
348
4.85
2.67
2.18
349
5.08
2.89
2.19
350
5.3
3.12
2.18
351
5.53
3.35
2.18
352
5.76
3.58
2.18
353
5.98
3.83
2.15
354
6.21
4.07
2.14
355
6.43
4.32
2.11
356
6.65
4.58
2.07
357
6.87
4.84
2.03
358
7.09
5.1
1.99
North
359
7.3
5.36
1.94
249.48
Figure of merit improvement
with 6 ft offset