Frequency : Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency. The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency.


UHF : Ultra High Frequency designates a range (frequency band) of electromagnetic waves with frequencies between 300 MHz and 3 GHz (3,000 MHz). Radio waves with frequencies above the UHF band fall into the SHF (Super high frequency) and EHF (Extremely high frequency) bands, all of which fall into the Microwave frequency range. Lower frequency signals fall into the VHF (Very high frequency) or lower bands.


VHF : Very High Frequency is the radio frequency range from 30 MHz to 300 MHz. Frequencies immediately below VHF are denoted High frequency (HF), and the next higher frequencies are known as Ultra high frequency (UHF). VHF propagation characteristics are ideal for short-distance terrestrial communication, with a range generally somewhat farther than line-of-sight from the transmitter (see formula below). Unlike high frequencies (HF), the ionosphere does not usually reflect VHF radio and thus transmissions are restricted to the local area (and don't interfere with transmissions thousands of kilometers away). VHF is also less affected by atmospheric noise and interference from electrical equipment than lower frequencies. Whilst it is more easily blocked by land features than HF and lower frequencies, it is less affected by buildings and other less substantial objects than UHF frequencies.


Repeater : A repeater is an electronic device that receives a signal and retransmits it at a higher level and/or higher power, or onto the other side of an obstruction, so that the signal can cover longer distances without degradation.


Mobile Radio : A two-way radio communication device designed to be installed in vehicle for higher powered communication. Typically higher powered than handheld radios.


Base Station : A two-way radio communication device designed to be installed at a desk or control station for higher powered communication. Typically higher powered than handheld radios.


Walkie-Talkie : A hand-held battery-operated radio transmitter and receiver often used by emergency personnel to communicate with one another. The first radio receiver/transmitter to be widely nick-named "Walkie-Talkie" was the backpacked Motorola SCR-300, created by an engineering team in 1940 at the Galvin Manufacturing Company (fore-runner of Motorola). The team consisted of Dan Noble, who conceived of the design using frequency modulation, Henryk Magnuski who was the principal RF engineer, Marion Bond, Lloyd Morris, and Bill Vogel.


Handie-Talkie : A device that could be held entirely in the hand (but had vastly reduced performance). Originally derived from the Motorola hand-held AM SCR-536 radio during World War II. This term is often confused with the original term ”Walkie-talkie” which referred to the back mounted model. Both devices ran on vacuum tubes and used high voltage dry cell batteries.


Frequency Modulation : In telecommunications, frequency modulation (FM) conveys information over a carrier wave by varying its frequency (contrast this with amplitude modulation, in which the amplitude of the carrier is varied while its frequency remains constant). In analog applications, the instantaneous frequency of the carrier is directly proportional to the instantaneous value of the input signal. Digital data can be sent by shifting the carrier's frequency among a set of discrete values, a technique known as frequency-shift keying.


Intrinsically Safe (IS or FM Approved) : Intrinsically safety (IS) is a protection technique for safe operation of electronic equipment in explosive atmospheres usually determined by Factory Mutual (FM) a third party certification. The concept was developed for safe operation of process control instrumentation in hazardous areas, particularly North Sea gas platforms. As a discipline, it is an application of Inherent safety in Instrumentation.


Analog : An analog or analogue signal is any continuous signal for which the time varying feature (variable) of the signal is a representation of some other time varying quantity, i.e. analogous to another time varying signal. It differs from a digital signal in that small fluctuations in the signal are meaningful. Analog is usually thought of in an electrical context; however, mechanical, pneumatic, hydraulic, and other systems may also convey analog signals.


Digital : The term digital signal is used to refer to more than one concept. It can refer to discrete-time signals that have a discrete number of levels, for example a sampled and quantified analog signal, or to the continuous-time waveform signals in a digital system, representing a bit-stream. In the first case, a signal that is generated by means of a digital modulation method is considered as converted to an analog signal, while it is considered as a digital signal in the second case.


Two Way Radio : A two-way radio is a radio that can both transmit and receive (a transceiver), unlike a broadcast receiver, which only receives content. Two-way radios are available in mobile, stationary base and hand-held portable configurations. Hand-held radios are often called walkie-talkies or handie-talkies. A push-to-talk or Press To Transmit button is often present to activate the transmitter. A mobile phone or cellular telephone is an example of a two-way radio that both transmits and receives at the same time (or full-duplex). It uses two different radio frequencies to carry the two directions of the conversation simultaneously.


Business Radio : High powered two-way radio (walkie-talkie) designed for government and enterprise communications.


Land Mobile Radio : Land Mobile Radio System (LMRS) is a term that denotes a wireless communications system(s) intended for use by terrestrial users in vehicles (mobiles) or on foot (portables). Such systems are used by emergency first responder organizations, public works organizations, or companies with large vehicle fleets or numerous field staff. Such a system can be independent, but often can be connected to other fixed systems such as the public switched telephone network (PSTN) or cellular networks. Also called Public Land Mobile Radio or Private Land Mobile Radio.


Portable Radio : A portable two-way radio is a radio that can both transmit and receive (a transceiver), unlike a broadcast receiver, which only receives content.


Hand-Held Radio : A handheld two-way radio is a radio that can both transmit and receive (a transceiver), unlike a broadcast receiver, which only receives content.


Consumer Radio : Low powered two-way radio (walkie-talkie) designed for basic personal use.


Amateur Radio : Amateur radio, often called ham radio, is both a hobby and a service in which participants, called "hams," use various types of radio communications equipment to communicate with other radio amateurs for public service, recreation and self-training. Amateur radio operators enjoy personal (and often worldwide) wireless communications with each other and are able to support their communities with emergency and disaster communications if necessary, while increasing their personal knowledge of electronics and radio theory. An estimated six million people throughout the world are regularly involved with amateur radio. The term "amateur" is not a reflection on the skills of the participants, which are often quite advanced; rather, "amateur" indicates that amateur communications are not allowed to be made for commercial or money-making purposes.


Ham Radio : Ham is an informal term for an amateur radio operator, and, by extension, "ham radio" refers to amateur radio in general. This use of the word first appeared in the United States during the opening decade of the twentieth century — for example, Robert A. Morton in "Wireless Interference", from the April, 1909 Electrician and Mechanic, reported overhearing an amateur radio transmission which included the comment: "Say, do you know the fellow who is putting up a new station out your way? I think he is a ham." However, the term did not gain widespread usage in the United States until around 1920, after which it slowly spread to other English-speaking countries.


eXRS : eXtreme Radio Service (eXRS) two-way radios use proprietary Frequency Hopping Spread Spectrum (FHSS) in the ISM band (900 MHz frequencies). This FHSS system combines the power of digital technology with narrow band FM modulation technique. Merging the two technologies facilitates a radio communications system that maintains a narrow band base signal to ensure for maximum usable range within a given dB power budget, comparable to traditional fixed frequency narrow band FM radios, but with the added benefit of wide band digital security and privacy provided by the frequency hopping spread spectrum algorithm. Maintaining the information signal as narrow band FM modulation centered on discrete frequencies allows for a large pool of non-overlapping hopping frequencies to draw upon within a given section of the radio frequency (RF) spectrum. The pseudo-random drawing of the hopping frequencies spreads the total signal power equally over the entire bandwidth of the RF spectrum used, which ensures minimal interference between many simultaneous, independent users.


P25 : Project 25 (P25) or APCO-25 refer to a suite of standards for digital radio communications for use by federal, state/province and local public safety agencies in North America to enable them to communicate with other agencies and mutual aid response teams in emergencies. In this regard, P25 fills the same role as the European Tetra protocol, although not interoperable with it. P25 was established to address the need for common digital public safety radio communications standards for First Responders and Homeland Security/Emergency Response professionals. TIA TR-8 facilitates such work through its role as an ANSI-accredited Standards Development Organization (SDO).


Frequency Band : A frequency range or frequency band is a range of wave frequencies (Low Band 30-100MHz, VHF 100-300MHz, UHF 300-600MHz, 800MHz or 900MHz). It most often refers to either a range of frequencies in sound or a range of frequencies in electromagnetic radiation, which includes light and radio waves.


MHz : Symbol for megahertz. The hertz (symbol: Hz) is a measure of frequency per unit of time, or the number of cycles per second. It is the basic unit of frequency in the International System of Units (SI), and is used worldwide in both general-purpose and scientific contexts. Hertz can be used to measure any periodic event; the most common uses for hertz are to describe radio and audio frequencies, more or less sinusoidal contexts in which case a frequency of 1 Hz is equal to one cycle per second.


MIL SPEC 810 : The MIL-STD-810 series of standards are issued by the United States Army's Developmental Test Command, to specify various environmental tests to simulate conditions that the tested item will encounter in the field. The current revision, as of 2008, is revision G (i.e. MIL-STD-810G), issued October 31, 2008, superseding revision F (MIL-STD 810F) from January 1, 2000 (last changed May 5, 2003). The methods listed below, along with others, simulate specific environmental conditions, and are referred to by the specification for the device. There is no certification, qualification or approval from the military although in the course of complying with a contract to supply material that the vendor has tested using MIL-STD-810 procedures, the procuring activity may accept such results as compliant with the contract specification. For instance (where the older 810E is an example):

  • MIL-STD 810E Method 500.3 Low Pressure (a.k.a. Altitude testing)
  • MIL-STD 810E Method 501.3 High Temperature (Both storage and operating)
  • MIL-STD 810E Method 502.3 Low Temperature (Both storage and operating)
  • MIL-STD 810E Method 503.3 Temperature Shock (How well does the device handle going from high to low temps, and back)
  • MIL-STD 810E Method 506.3 Rain (How does the device do in wind blown rain)
  • MIL-STD 810E Method 507.3 Humidity (Can the device handle high Humidity)
  • MIL-STD 810E Method 508.4 Fungus (device is exposed to warm moist air in the presence of Fungus to see if it grows on the device)
  • MIL-STD 810E Method 509.3 Salt Fog (does the device rust/fail when exposed to salt fog)
  • MIL-STD 810E Method 510.3 Sand and Dust (how well does the device work when exposed to sand and dust)
  • MIL-STD 810E Method 511.3 Explosive Atmosphere (does the device create enough sparks/etc to cause an explosive atmosphere to blow up)
  • MIL-STD 810E Method 512.3 Leakage
  • MIL-STD 810E Method 513.4 Acceleration (constant acceleration)
  • MIL-STD 810E Method 516.4 Shock (either Shock Response Spectrums, or triangle / sine / square wave shocks) — also transport shock
  • MIL-STD 810E Method 519.4 Gunfire Vibration
  • MIL-STD 810E Method 520.1 Temp, Humidity, Vibration (Traditionally sine wave (pre D), later random vibration — combined with Temp testing)
  • MIL-STD 810E Method 521.1 Icing, Freezing Rain