A-Index: Long term stability of Earth's Geomagnetic field. The A-index is a geomagnetic index that measures the daily average level of geomagnetic activity. It's calculated by averaging eight three-hourly "a" indices. The A-index is used to describe how solar events like coronal mass ejections and solar flares cause disturbances in the Earth's magnetic field.
Band Pass | Band Pass Frequency | Band Pass Filter: A ham radio's band pass is the range of frequencies that can pass through a bandpass filter in a radio receiver. The filter allows signals within a selected frequency range to be heard or decoded, while blocking signals at other frequencies. Signals outside the receiver's tuned band can damage or saturate it.
Coronal Mass Ejection: A coronal mass ejection (CME) is a massive burst of plasma and magnetic fields from the Sun's upper atmosphere, or corona. CMEs are often associated with solar flares.
Critical Angle: Critical angle is the highest takeoff angle that will return a radio wave to Earth under specific ionospheric conditions.
Critical Frequency: Critical Frequency is the highest frequency which is refracted back to Earth.
Digital Modes: Digital modes are a means of transmitting sound, text or other information using a set number of discrete frequency or phase shifts. This is achieved via ham radio using personal computers, soundcards and software. The bandwidth is usually narrower than voice and digital modes work well with low power.
Ferrite Beads\Choke: Ferrite beads, often called Ferrite chokes or Ferrite rings, are passive electronic components that help suppress radio frequency interference (RFI) on a power supply line. They can be a very useful tool in your sound bar or powered monitor set up and should take you less then 5 minutes to install!
Flutter: Flutter is an acoustic effect that occurs when incoming signals are not exactly equal, causing them to reinforce and oppose each other. This results in a rapid variation of signal parameters, such as amplitude, phase, and frequency. Ham radio operators used to call this phenomenon "rapid QSB". As the difference between the two signals increases, the flutter speed increases until it becomes an audible tone or squeal, also known as a heterodyne squeal. In general, flutter can be caused by a number of things, including: Atmospheric disturbances, Antenna movements in high winds, Interaction with other signals, and Reflection and partial absorption of signals by aircraft flying through the radio beam.
Geometric Activity/Storms: Geomagnetic activity is the level of magnetism in the Earth's field, which is driven by solar activity. The level of geomagnetic activity is measured using the planetary K index (Kp), which ranges from 0 to 9; Kp 0–2: The aurora is dim and far north; Kp 3–5: The aurora is brighter and moves further from the poles; Kp 6–7: The aurora is very bright and active, and may be visible from the northern edge of the United States; Kp 8–9: The aurora is very bright and active, and may be visible directly overhead from the northern states of the United States; When geomagnetic activity is high, the aurora can be visible for longer periods of time, including in the evening and morning
HF Scatter: Sometimes shows up as flutter and/or Aurora Flutter sometimes plague HF Scatter. HF scatter, or ionospheric scatter propagation, is a mode of radio wave propagation that occurs when a radio signal is scattered by the ionosphere and received by another station. This mode is best for medium-range communication at frequencies between 20 and 50 MHz.
High Frequency/HF: HF stands for high frequency, which is a band of radio waves that range from 3 to 30 MHz. The ionosphere is a layer of the Earth's atmosphere that extends from 50 to 600 miles above the surface. The free electrons in the ionosphere cause HF radio waves to refract, or bend, and eventually reflect back to Earth.
Inductor: An inductor is a passive electrical component that stores energy in a magnetic field when an electric current passes through it. Inductors are also known as chokes, coils, or reactors. Inductors are used in many electrical circuits to: Handle fluctuations in electric current, store and transfer energy in power converters, block, attenuate, choke, or filter high frequency noise Inductors work by using the relationship between the magnetic field and the electric current to compensate for changes in the current's flow. For example, when the current increases, the inductor's magnetic field strengthens, which induces a voltage that opposes the change. The electrical symbol for an inductor is L. The SI unit of inductance is the Henry, named after American scientist Joseph Henry.
Linearity: An amplifier's linearity is its ability to increase the power of an input signal without altering its content or shape. A linear amplifier produces an output signal that is a proportional copy of the input signal. Linearity is important for preserving the integrity of modulation formats used to achieve high data rates. It's also important for systems that encode information in the amplitude variation of the signal, such as those using Amplitude Modulation (AM) or Quadrature Amplitude Modulation (QAM). Linearity is characterized by a number of parameters, including: Carrier-to-intermodulation (C/I) ratio, Noise power ratio (NPR), Adjacent-channel power ratio (ACPR), and Error vector magnitude (EVM). Linearity is often at odds with efficiency, which is the ratio of the output power to the input power. Efficient amplifiers consume less power and generate less heat, which is desirable for compact devices and those powered by batteries. However, efficient amplifiers often operate in a nonlinear region, which introduces distortion and harmonics
LUF: LUF is the Lowest Usable Frequency for communications between two specific points. Radio waves on frequencies below the LUF are attenuated before reaching the destination. That is a technical way of saying “your signal doesn’t get through.” If the LUF exceeds the MUF, your signal doesn’t get through. Saying that differently, propagation via ordinary skywave communications is not possible over that path.
MUF: MUF stands for the Maximum Usable Frequency for communications between two points. All the factors we have discussed up until now affect the MUF including: Path distance and location; Time of day and season; or Solar radiation and ionospheric disturbances.
Offset: To use a repeater, you must have a transceiver that can transmit on the repeater's input frequency and receive on the repeater's output frequency. The input and output frequencies are separated by a predetermined amount that is different for each band. This separation is called the offset.
Ohms Law: The law states that electric current is proportional to voltage and inversely proportional to resistance. V=I*R
POTA: Parks on the Air
PWM: Pulse Width Modulation (PWM) is a technique used in Arduino to create analog results using digital means. PWM works by generating a square wave, which is a signal that switches between on and off. The duration of time the signal is on is called the pulse width, and changing the pulse width creates different analog values. PWM controller PWM is used to control electric power inside a motor coil. The output power is controlled by repeatedly turning the output on and
Resistor/Resistance: Resistors have an apt name: They “resist” the electrical current going through them. You can think of resistors as “brakes” for electrons. By controlling the electrons going through a resistor, you can make a circuit do different things.
Resonate Antenna: Resonant antennas are also called "resonant-length antennas", as their length is designed to be a multiple of a quarter wavelength, which allows them to resonate at a specific frequency with minimal reactance and maximum current flow.
RTTY: Radio TeleTYpe (RTTY) is a method of sending digital messages between radios using tones. It's a digital mode used in ham radio that can be conversational, similar to technical conversation or rag chewing.
SOTA: Summits on the Air
Voltage: Voltage is the pressure from an electrical circuit's power source that pushes charged electrons (current) through a conducting loop, enabling them to do work such as illuminating a light. In brief, voltage = pressure, and it is measured in volts (V). The term recognizes Italian physicist Alessandro Volta (1745-1827), inventor of the voltaic pile—the forerunner of today's household battery.
Watts: A watt (W or P) is a unit of power that measures the rate at which energy is used or generated. It's a standard unit in the International System of Units (SI) and is derived from the kilogram, meter, and second. One watt is equal to one joule of energy per second. Formula for find Watts P = I x V
