Topband: Monster antennas

[k6se@juno.com]

Ford, N0FP wrote (regarding monster verticals):

"Does 200' play better on 160M than 130'?
 
Rohn makes an insulated section for the 45G.  Does insulating it make
sense?"
==========
To me, insulating a tower to series feed it does not make sense because
you can just as efficiently shunt feed a grounded tower.

Regarding how tall a vertical is, if you study the following tables
derived from EZNEC modeling it will appear evident that no or very little
added gain is realized by having a vertical that is taller than 1/4
wavelength unless the soil conductivity in your area is better than "very
good".  The reason for this is that when the vertical gets taller, the
radiation angle gets lower and the far field ground loss "sucks out" the
gain which might be realized for the bigger vertical.  The 1/4-wave
vertical also has the advantage of having a wider 2:1 SWR operating
bandwidth than any other size vertical.

73, de Earl, K6SE


          OVER "VERY POOR" GROUND:
 
VERTICAL  dBi GAIN  @TOA  -3 dB POINTS
--------  --------  ----  ------------
1/8-WAVE   -0.61    30.0   10.8  57.5
1/4-WAVE   -0.98    27.6   10.1  54.1
3/8-WAVE   -1.30    23.9    9.0  47.0
1/2-WAVE   -1.19    19.9    7.8  38.3
5/8-WAVE    0.04    17.4    6.9  63.0


            OVER "POOR" GROUND:
 
VERTICAL  dBi GAIN  @TOA   -3 dB POINTS
--------  --------  ----  ------------
1/8-WAVE    0.53    27.5    9.0  55.9
1/4-WAVE    0.32    25.3    8.5  52.4
3/8-WAVE    0.16    21.9    7.7  45.3
1/2-WAVE    0.26    18.1    6.7  35.8
5/8-WAVE    0.76    14.6    5.7  29.5


            OVER "GOOD" GROUND:
 
VERTICAL  dBi GAIN  @TOA   -3 dB POINTS
--------  --------  ----  ------------
1/8-WAVE    1.57    24.6    7.3  54.0
1/4-WAVE    1.42    22.7    6.9  50.3
3/8-WAVE    1.31    19.6    6.3  43.1
1/2-WAVE    1.36    16.1    5.6  33.4
5/8-WAVE    1.35    12.6    4.7  24.7


          OVER "VERY GOOD" GROUND:
 
VERTICAL  dBi GAIN  @TOA   -3 dB POINTS
--------  --------  ----  ------------
1/8-WAVE    3.11    18.7    4.0  50.4
1/4-WAVE    3.16    17.2    3.9  46.4
3/8-WAVE    3.36    14.9    3.6  39.2
1/2-WAVE    3.31    12.3    3.3  30.2
5/8-WAVE    4.21     9.7    2.9  21.4


             OVER SALT WATER:
 
VERTICAL  dBi GAIN  @TOA   -3 dB POINTS
--------  --------  ----  ------------
1/8-WAVE    4.54     8.0    0.5  45.1
1/4-WAVE    4.81     7.4    0.5  40.8
3/8-WAVE    5.33     6.4    0.4  33.8
1/2-WAVE    6.26     5.4    0.4  25.8
5/8-WAVE    7.41     4.3    0.4  18.2