THE IONOSPHERE:
The ionosphere is an electrically charged region of atmospheric gases that surround the Earth. Ionization (electric charge) happens when solar radiation bombards atmospheric gas molecules and forces them to detach electrons leaving the gas molecule with a positive electrical charge called an ion and leaving free electrons in the atmosphere.
Since positive electrical charges repel each other the gas ions tend to "bunch" in distinct "layers" of ions at heights of between 30 and 300 miles shown in fig 4. These charged areas will reflect radio signals back to earth if they strike the ionosphere at particular angles using particular frequency bands. Radio engineers have labeled these layers the D, E, F I and F2 layers (see fig 4). 3 factors determine whether a radio signal will be reflected back to earth and can be used by Brigade THFRS Communications systems.
They are:
(1) the higher the radio frequency the more likely the signal will penetrate the ionosphere rather than be reflected by it,
(2) the current ion density determined by the amount of sun light (time of day, season, solar activity) at the time communications is desired, and
(3) the angle at which the radio wave contacts the ionosphere. See figure 5 for details. Note - that at any time of the day, year, or solar activity (sunspot) cycle there is
always available a band of radio frequencies that can be reflected off the ionosphere and will support HF communications. The Automatic Link Establishment (ALE) feature of THFRS will find these frequencies for the operator from the list of authorized frequencies in the radio database. Signals on these frequencies can be used for Brigade tactical HF communications over distances of hundreds of miles unless very unusual and rare solar activity is occurring. Also note that the angle at which the wave front contacts the reflecting layer is determined by the radios antenna system. Low angles of radiation are produced by the OE-5 05 and AT- IO 1 1 vertical whips and high angle radiation is produced by bending the whips into the horizontal position with the whip tilt adaptor or by using the RF- 1 912 or RF- 1 941 wire dipole antennas 30 feet OR LESS above ground.
The ionosphere is an electrically charged region of atmospheric gases that surround the Earth. Ionization (electric charge) happens when solar radiation bombards atmospheric gas molecules and forces them to detach electrons leaving the gas molecule with a positive electrical charge called an ion and leaving free electrons in the atmosphere.
Since positive electrical charges repel each other the gas ions tend to "bunch" in distinct "layers" of ions at heights of between 30 and 300 miles shown in fig 4. These charged areas will reflect radio signals back to earth if they strike the ionosphere at particular angles using particular frequency bands. Radio engineers have labeled these layers the D, E, F I and F2 layers (see fig 4). 3 factors determine whether a radio signal will be reflected back to earth and can be used by Brigade THFRS Communications systems.
They are:
(1) the higher the radio frequency the more likely the signal will penetrate the ionosphere rather than be reflected by it,
(2) the current ion density determined by the amount of sun light (time of day, season, solar activity) at the time communications is desired, and
(3) the angle at which the radio wave contacts the ionosphere. See figure 5 for details. Note - that at any time of the day, year, or solar activity (sunspot) cycle there is
always available a band of radio frequencies that can be reflected off the ionosphere and will support HF communications. The Automatic Link Establishment (ALE) feature of THFRS will find these frequencies for the operator from the list of authorized frequencies in the radio database. Signals on these frequencies can be used for Brigade tactical HF communications over distances of hundreds of miles unless very unusual and rare solar activity is occurring. Also note that the angle at which the wave front contacts the reflecting layer is determined by the radios antenna system. Low angles of radiation are produced by the OE-5 05 and AT- IO 1 1 vertical whips and high angle radiation is produced by bending the whips into the horizontal position with the whip tilt adaptor or by using the RF- 1 912 or RF- 1 941 wire dipole antennas 30 feet OR LESS above ground.