[TowerTalk] Low beam vs. higher dipoles?
David O Hachadorian
k6ll@juno.com
Fri, 09 May 1997 14:38:52 EDT
On Thu, 8 May 1997 21:41:15 -0500 "Jeff Shelton" <cshelton@pop.erols.com>
writes:
>You see, I just moved to a new house, and my situation there will
>allow me to put dipoles up in trees about 45-55 feet above ground. I
>can also put up a modest roof tower, but I will only be able to get a
>beam up about 25 feet.
Here is a little comparison of dipoles at 50' in their favored
direction vs. a 5 dBd gain tribander at 25'. Tribander
freespace gain is assumed to be 5 dBd, constant over the
first 20 degrees of elevation. The beam has a significant
advantage at the higher range of angles, and is roughly
comparable to the higher dipole at lower angles. The beam has
the additional advantage of being rotatable, and would be much
better in the dipoles' unfavorable directions.
height in feet: 50 height in feet: 25
frequency, Mhz: 14 frequency, Mhz: 14
wavelengths: 0.711 wavelengths: 0.356
ant gain dBi: 2.1 ant gain dBi: 7
GAIN GAIN
angle dBi angle dBi
1 -14.07 1 -15.18
2 -8.07 2 -9.17
3 -4.60 3 -5.66
4 -2.16 4 -3.18
5 -0.31 5 -1.26
6 1.17 6 0.29
7 2.39 7 1.60
8 3.41 8 2.72
9 4.27 9 3.69
10 5.01 10 4.56
11 5.64 11 5.33
12 6.17 12 6.03
13 6.63 13 6.66
14 7.02 14 7.23
15 7.33 15 7.76
16 7.59 16 8.24
17 7.79 17 8.68
18 7.94 18 9.08
19 8.04 19 9.46
20 8.09 20 9.80
--------------------------------------
height in feet: 50 height in feet: 25
frequency, Mhz: 21 frequency, Mhz: 21
wavelengths: 1.067 wavelengths: 0.534
ant gain dBi: 2.1 ant gain dBi: 7
GAIN GAIN
angle dBi angle dBi
1 -10.56 1 -11.66
2 -4.60 2 -5.66
3 -1.18 3 -2.16
4 1.18 4 0.30
5 2.93 5 2.19
6 4.29 6 3.71
7 5.36 7 4.98
8 6.20 8 6.06
9 6.86 9 6.99
10 7.36 10 7.80
11 7.73 11 8.52
12 7.96 12 9.15
13 8.08 13 9.71
14 8.09 14 10.21
15 7.98 15 10.65
16 7.76 16 11.04
17 7.42 17 11.39
18 6.96 18 11.69
19 6.36 19 11.96
20 5.60 20 12.19
----------------------------------------
height in feet: 50 height in feet: 25
frequency, Mhz: 28 frequency, Mhz: 28
wavelengths: 1.423 wavelengths: 0.711
ant gain dBi: 2.1 ant gain dBi: 7
GAIN GAIN
angle dBi angle dBi
1 -8.07 1 -9.17
2 -2.16 2 -3.17
3 1.18 3 0.30
4 3.43 4 2.74
5 5.03 5 4.59
6 6.21 6 6.07
7 7.05 7 7.29
8 7.63 8 8.31
9 7.97 9 9.17
10 8.10 10 9.91
11 8.02 11 10.54
12 7.74 12 11.07
13 7.23 13 11.53
14 6.48 14 11.92
15 5.44 15 12.23
16 4.04 16 12.49
17 2.14 17 12.69
18 -0.53 18 12.84
19 -4.70 19 12.94
20 -13.41 20 12.99
Dave Hachadorian, K6LL
k6ll@juno.com
--
FAQ on WWW: http://www.contesting.com/towertalkfaq.html
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com