Nw3z Antenna Designs
Nw3z Antenna Designs
Nw3z Antenna Designs
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The antenna design was optimized in free space and has the following remarkable characteristics across the
band: VSWR < 1.2, F/B > 23dB and Gain > 10dBi.
1.25
1.2
1.15
1.1
VSWR
1.05
1
14.000
14.100
14.200
14.300
35
30
25
Gain
F/B
20
15
10
5
14.000
14.100
14.200
14.300
The spacing of each element is shown from the reflector and all lengths represent the exposed length of
tubing. Double wall sections are indicated below the table. The taper schedule of the elements can be
adjusted using YO (using the W6QHS algorithm).
The 20m Antenna
1
0.875
0.75
0.625
0.5
0.00
48
24
44
36
65.73
90.00
48
24
44
36
58.70
139.52
48
24
44
36
48.80
226.70
48
24
44
36
42.62
388.44
48
24
44
36
42.63
570.00
48
24
44
36
35.39
* The 1.000, 0.875 and 0.750 sections are double wall sections
This antenna is, without doubt, the best antenna I have ever built. The side and back rejection are
absolutely phenomenal and the 1.5 VSWR bandwidth through 100 of Belden 9913 extends the entire way
from 20.000 MHz to 21.500 MHz! The element spacing is rather wide considering the boom length but
experimentation showed that the addition of a 7th element did not contribute anything to the performance.
For 15m we were fortunate in that the pattern of the optimized free space design is not degraded at all when
placed on the 185 tower at K3CR. This design has the following free space performance across the band:
VSWR < 1.3, F/B > 23dB and Gain > 11.2dBi. When this antenna is modeled on the 120 tower, such as
the one at K3LR, there is some loss of F/B at the top of the band but the overall performance is excellent.
The free-space performance of this antenna is shown below.
1.4
1.35
1.3
VSWR
1.25
1.2
1.15
1.1
1.05
1
21.000
21.100
21.200
21.300
21.400
21.300
21.400
34
32
30
28
26
24
Gain
22
F/B
20
18
16
14
12
10
21.000
21.100
21.200
The spacing of each element is shown from the reflector and all lengths represent the exposed length of
tubing. Double wall sections are indicated below the table. The taper schedule of the elements can be
adjusted using YO (using the W6QHS algorithm).
The 15m - 48 Design
0.75
0.625
0
36
24
82.4547
36
24
118.239
36
24
221.131
36
24
408.314
36
24
570
36
24
*the .75 section is double wall
0.5
83.5746
79.2662
74.0373
70.3034
66.9878
63.5933
26
24
22
20
Gain
18
F/B
16
14
12
10
21.000
21.050
21.100
21.150
21.200
21.250
21.300
21.350
21.400
21.450
2.2
VSWR
1.8
1.6
1.4
1.2
1
28.000
28.200
28.400
28.600
28.800
29.000
36
34
32
30
28
26
24
Gain
F/B
22
20
18
16
14
12
10
28.000
28.200
28.400
28.600
28.800
29.000
The spacing of each element is shown from the reflector and all lengths represent the exposed length of
tubing. Double wall sections are indicated below the table. The taper schedule of the elements can be
adjusted using YO (using the W6QHS algorithm).
0.5
64.81
62.13
57.49
54.84
51.47
51.07
47.28
The gain of the antenna is pretty much flat across the band at a little over 10dBi and the F/B is shown
below.
27
26
25
24
23
22
21
20
19
28.000
28.100
10m Elements
28.200
28.300
28.400
28.500
28.600
28.700
28.800
28.900
29.000
Diameter
0.750 0.625
Exposed Length
24
18
42
Total Tubing Length 24
reflector
driven element
director 1
director 2
director 3
director 4
0.500
tip length
tip+4"
spacing from
reflector
0
43.86
69.18
131.3
192.7
282.0
tip length
65.52
61.59
55.90
53.88
54.17
49.57
Here is a view of the antenna system immediately before the contest. For 3 weeks we had nothing but sunny
skies and blistering heat but the sky really opened up over the weekend! The 10m antenna was mounted
above the TIC Ring as can be seen in this picture. We were having some difficulty with the rotor and since
we had no need to turn any of the antennas for ARRL DX, I simply bolted the antenna to a tower leg. The
rotor has since been aligned and the 10m antenna is mounted on it (this is at the 30 level). To the right of
the photograph you can see the 3 element wire yagi for 40m. The boom was a rope catenary that ran about
500 across a valley to a secondary hill top that was within 10 degrees of the direction of central stateside!
For 80 and 160 there is an inverted-V with a common feedpoint. We are looking up between one of the
legs: the 80m element and insulator is seen to the left of the picture while the 160m leg continues past the
camera to the upper right.
Below is a view to stateside from the base of the tower. Note the Atlantic Ocean is in view for the entire
photograph!!
And here is the man! Angel, WP3R, tests out the station before the contest. Equipment is FT1000MP and
an AL-1500 which is vented to the outside through the flexible ducting.
The information for the 20m antenna is below. The gain ranges from 10.1 dBi to 10.3 dBi.
F/B
34
32
30
28
26
24
22
20
14.000
14.050
14.100
14.150
14.200
14.250
14.300
14.350
The performance for the 15m antenna is shown below. The gain is 9.3 dBi at the bottom of the band and
increases to 10.8 dBi near the top of the band.
F/B
32
30
28
26
24
22
21.450
21.400
21.350
21.300
21.250
21.200
21.150
21.100
21.050
21.000
20
The taper schedule for the antenna is as follows. The first table shows the inner half-element which is the
same for all. Note that the inner section is acutally triple walled for the 20m elements: these design come
directly from the ARRL Antenna Handbook 120mph specifications. The tip lengths are listed in the second
table.
20m Elements
Diameter
Exposed Length
Total Tubing Length
reflector
driven element
director 1
director 2
director 3
director 4
1.250
48
48
tip length
65.73
58.53
48.39
42.06
42.06
34.64
15m Elements
Diameter
0.875 0.750 0.625
Exposed Length
36
36
18
Total Tubing Length 36
72
22
reflector
driven element
director 1
director 2
director 3
director 4
spacing from
20m reflector
115
182.5
231.1
314.45
406.3
543.9
0.500
tip length
tip+4"
tip length
55.94
50.11
45.16
43.83
42.68
37.74
0.500
tip length
tip+4"
Conclusions
Well I hope you have gotten something out of this! Im sure that there are things that I forgot to say but you
should be able to take the information Ive given and get some pretty good antennas built. If you build any
of these antennas please drop me a line to let me know how everything worked out for you. I hope to see
many of you at Dayton this year: Im sure youll find me hanging around with such shady characters as
WA3FET, WP3R and KB3AFT and always near the contest activities hopefully somewhat sober!
73 Nathan NW3Z
NW3Z@contesting.com
Nathan Miller, NW3Z, has been extensively involved in the modeling and testing of HF antenna
systems since 1994. He received his BS degree with honors from Penn State University in 1996 and will
receive his MSEE degree in August 1998. While completing his MS degree, he has acted as an antenna
consultant to the Arecibo Observatory and the US Coast Guard Academy and has participated in several
government research contracts. He has also written articles for several publications, including QST and
NCJ. Currently, he is a serving line officer in the US Navy and will be reporting to USS Barry (DDG-52)
upon completion of Surface Warfare Officers School in Newport, RI.