Found an interesting read while looking up 'Maximum Usable Frequencies". That is a term used by Hams to determine just what freq's are possibly 'open' for DXing under the given propagation due to solar activity. But so does the 'Maximum Usable Angle'. The CBer using the 11m band can also benefit from this info.
We often hear the term 'angle of radiation' from the kind of antennas we use and choose to run with, such as a 5/8 or 1/2 wave antenna. Dipole or Yagi - etc. This chart can be helpful in seeing just how that translates to the real world, in terms of just what angle you might be getting now and what you may want to improve. Height above ground changes this angle of radiation, so does the type of antenna you use. The lowest angle is best for the best long path DXing, and vice versa. That is, if you are interested in long path skip/DXing.
For those new to these concepts, some info and help if you want to ask questions here.
Here is a quote from the Ken Larson/KJ6RZ page:
Source page:
Maximum Usable Angle
" . . . We are all relatively familiar with the term maximum usable frequency since it often appears as a question on amateur radio license exams. Maximum usable angle is the other half of the maximum usable frequency equation.
Maximum usable frequency is important for determining the best HF frequency to use in communicating between two locations, for example between Los Angles and Denver. The maximum usable frequency depends in part on the distance between to two locations. Thus the maximum usable frequency for communicating between Los Angles and San Diego will be different from that to communicate between Los Angles and Denver. In the past, maximum usable frequency was very important to professional communicators who were interested in operating full time HF communication circuits between specific locations, for example from Guam to North West Cape Australia. Today commercial HF circuits are probably less important than in the past because of the wide availability of communication satellites. Maximum usable frequency is still important to amateur radio operators interested in scheduling contacts with distant friends, communicating with a specific country, and in operating regional ARES/RACES HF emergency communication circuits.
For general amateur radio work, however, maximum usable angle is probably more important than maximum usable frequency. Maximum usable angle focuses on band availability, the types of antennas needed to take advantage of band openings, and the skip distances that can be expected . . . "
The main lobe elevation angle depends on the configuration of the transmitting antenna. Vertical antennas have low elevation angles while horizontal dipoles and yagi antennas have low to high elevation angles depending on their height (measured in wavelengths) above ground, as shown in the table below. The numbers in parentheses are the angles for the -3db points on the antenna's main lobe.
Antennas Elevation Angle in Degrees
Vertical
1/4 wavelength long 28 (15 - 40)
3/8 wavelength long 23 (12 - 35)
1/2 wavelength long 18 (09 - 25)
5/8 wavelength long 12 (07 - 18)
Hortizontal Dipole
1/8 wavelength long above ground 90 (55 for lower 3db point)
1/4 wavelength long above ground 60 (38 - 82)
1/2 wavelength long above ground 30 (18 - 40)
3/4 wavelength long above ground 21 (14 - 28)
One wavelength long above ground 17 (09 - 19)
Hortizontal Yagi
1/4 wavelength long above ground 43 (32 - 54)
1/2 wavelength long above ground 30 (18 - 38)
3/4 wavelength long above ground 21 (13 - 28)
One wavelength long above ground 17 (09 - 18)
We often hear the term 'angle of radiation' from the kind of antennas we use and choose to run with, such as a 5/8 or 1/2 wave antenna. Dipole or Yagi - etc. This chart can be helpful in seeing just how that translates to the real world, in terms of just what angle you might be getting now and what you may want to improve. Height above ground changes this angle of radiation, so does the type of antenna you use. The lowest angle is best for the best long path DXing, and vice versa. That is, if you are interested in long path skip/DXing.
For those new to these concepts, some info and help if you want to ask questions here.
Here is a quote from the Ken Larson/KJ6RZ page:
Source page:
Maximum Usable Angle
" . . . We are all relatively familiar with the term maximum usable frequency since it often appears as a question on amateur radio license exams. Maximum usable angle is the other half of the maximum usable frequency equation.
Maximum usable frequency is important for determining the best HF frequency to use in communicating between two locations, for example between Los Angles and Denver. The maximum usable frequency depends in part on the distance between to two locations. Thus the maximum usable frequency for communicating between Los Angles and San Diego will be different from that to communicate between Los Angles and Denver. In the past, maximum usable frequency was very important to professional communicators who were interested in operating full time HF communication circuits between specific locations, for example from Guam to North West Cape Australia. Today commercial HF circuits are probably less important than in the past because of the wide availability of communication satellites. Maximum usable frequency is still important to amateur radio operators interested in scheduling contacts with distant friends, communicating with a specific country, and in operating regional ARES/RACES HF emergency communication circuits.
For general amateur radio work, however, maximum usable angle is probably more important than maximum usable frequency. Maximum usable angle focuses on band availability, the types of antennas needed to take advantage of band openings, and the skip distances that can be expected . . . "
The main lobe elevation angle depends on the configuration of the transmitting antenna. Vertical antennas have low elevation angles while horizontal dipoles and yagi antennas have low to high elevation angles depending on their height (measured in wavelengths) above ground, as shown in the table below. The numbers in parentheses are the angles for the -3db points on the antenna's main lobe.
Antennas Elevation Angle in Degrees
Vertical
1/4 wavelength long 28 (15 - 40)
3/8 wavelength long 23 (12 - 35)
1/2 wavelength long 18 (09 - 25)
5/8 wavelength long 12 (07 - 18)
Hortizontal Dipole
1/8 wavelength long above ground 90 (55 for lower 3db point)
1/4 wavelength long above ground 60 (38 - 82)
1/2 wavelength long above ground 30 (18 - 40)
3/4 wavelength long above ground 21 (14 - 28)
One wavelength long above ground 17 (09 - 19)
Hortizontal Yagi
1/4 wavelength long above ground 43 (32 - 54)
1/2 wavelength long above ground 30 (18 - 38)
3/4 wavelength long above ground 21 (13 - 28)
One wavelength long above ground 17 (09 - 18)
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