Elecraft KX3 Owner's Manual - Manual (Page 52)

52
Glossary of Selected Terms
The following terms are often used in the discussion of amateur radio transceivers and related equipment. All
are directly applicable to the KX3, which is used here to illustrate some of the concepts. A much larger glossary
of terms can be found in the ARRL Handbook and on numerous web sites.
________________
A-to-D or ADC (analog-to-digital converter): An integrated circuit that converts analog electrical signals such
as audio or RF into digital form. The digital signals can then be processed by a digital signal processor, or DSP
(see below).
AF, RF, and IF: AF stands for audio frequencies—usually, sounds that you can hear. RF, or radio frequencies,
are the actual frequencies of the radio signals (or TV, or cell phone, etc.). IF, or intermediate frequencies, are
generally somewhere between RF and AF. In a receiver, it is usually advantageous to convert RF signals to a
lower IF at which is it more practical to obtain gain or selectivity. These IF signals are then further converted to
AF and amplified further so they can be used to drive headphones or speakers.
Attenuator: A circuit that reduces signals to a safe level for use by subsequent stages in a receiver. The KX3
includes two switchable attenuators, one under control of the user (pg. 13), the other switched in automatically
as needed (pg. 45, under COR).
ATU (automatic antenna tuner): A device inserted between a transmitter (or transceiver) and an antenna that
establishes an optimal match between the two, thus allowing full power transfer. (See KXAT3, pg. 25.)
D-to-A or DAC (digital-to-analog converter): An integrated circuit that converts digital signals into analog
form, such as audio or RF. Also see DSP, below.
dB (decibel): A measure of signal increase or decrease, or of one signal relative to another signal. In human
terms, one dB represents a “just noticeable difference” between two signals (or a just-noticeable increase or
decrease). Mathematically, dB is derived from the ratio of two signals. Receivers must handle signals over a
huge range—in excess of 100 dB. dBm is a more specific term that means “dB relative to 1 milliwatt.” 1
milliwatt is considered to be a “0 dBm” signal in this case.
DC-to-DC converter: A device that converts one DC voltage into another. For example, the KX3 includes a
very efficient DC-to-DC converter that converts 12 V (nominal) at the DC input jack to 3.3 V for use by its low-
voltage circuitry. The advantage of a DC-DC converter is that when it steps voltage down, it steps current up (or
vice-versa). In this case, the 300 mA the KX3 consumes at 3.3 V might require only 100 mA at the 12-V power
source.
DSP (digital signal processor): A highly specialized numeric computer, implemented on a single integrated
circuit, that processes signals digitally. Inputs to the DSP must generally be converted from analog to digital
form (see A-to-D, above), while outputs from the DSP must be converted from digital to analog (see D-to-A).
Use of DSP techniques can result in greater versatility and smaller size compared to the equivalent analog
circuitry. The KX3 uses a very advanced, power-efficient DSP.
ESD (electrostatic discharge): An event during which high voltages or currents appear within a radio or other
electronic device, potentially causing damage. Antennas, control cables, or the operator’s body are all potential
ESD sources. Damage can be avoided through proper handling and grounding techniques.
HF (high-frequency): Signals in the range of 3 to 30 MHz. In amateur radio, HF is also shorthand for 160-10
meters (1.8 to 29.7 MHz), or the “HF bands.” 160 meters actually falls in the MF range (0.3 to 3 MHz). The 6-
meter band (50-54 MHz) is often included in “HF” transceivers, though it is actually in the VHF (very high-
frequency) range of 30-300 MHz.
IMD (intermodulation distortion): Unwanted signal products that are created in the various stages of a
receiver or transmitter. If all stages were entirely “clean,” there would be no IMD. In reality, every stage
contributes some distortion, with the amount of distortion being proportional to signal level. Radio designers go