Radio was not invented by any single person, but instead was a culmination of several scientists’ research, each of whom pioneered a different area of electromagnetic radiation and radio waves during the late 1800s and early 1900s. Among these men are well known researchers such as Heinrich Rudolf Hertz, James Clerk Maxwell, David E. Hughes, …
GMRS (General Mobile Radio Service) is a licensed radio service. GMRS consists of 16 UHF channels on FM, plus 7 channels that are shared with FRS. The maximum allowable power for a GMRS radio is 50 watts. The GMRS channels which are shared with FRS are limited to 5 watts of power. The use of …
The SMA (SubMiniature Type A) connector is a type of the radio frequency connector developed in the 1960s to make it easier to connect coaxial cables. Using a screw-type design instead of the common ‘push-pull’ system, the SMA connector allows for a quick connection; and can be used in both alternating and direct current applications. …
dBm is the standard unit of measure for levels of power based on a one milliwatt (mW) reference signal. The dBm measurement is very similar to dB (decibel); however, dB is a relative measure of the power of an input signal while dBm is always an absolute value based on a single milliwatt. If there …
The military alphabet, or more properly the phonetic alphabet, exists in innumerable variants. If any military alphabet can be viewed as the most correct, it is the current NATO standard military alphabet. However, even with the NATO standard military alphabet, various member nations use numerous spelling variations. This version of the military alphabet is also …
Yagi Antennas are one of the most well-known directional antennas in use throughout the world and are used for communications in the medium range of three to five miles between two points. They can also be used as a bridge antenna to connect clients to an access point. The original inventors of the antenna design …
Intersymbol interference is a signal distortion in telecommunication. One or more symbols can interfere with other symbols causing noise or a less reliable signal. The main causes of intersymbol interference are multipath propagation or non-linear frequency in channels. This has the effect of a blur or mixture of symbols, which can reduce signal clarity. If …
A bug detector is a device that is able to locate and/or disable electronic spy equipment such as microphones, cameras, and GPS tracking devices. Law enforcement agencies, military counter-intelligence agencies, criminals, and everyday individuals who are suspicious of being overheard often use bug detectors. Bug detectors are usually small, portable, and have multiple display functions …
A police scanner is basically a radio scanner that is also a receiver that receives wireless radio signals. A scanner identifies these wireless radio waves. A scanner can identify numerous radio signals and bands concurrently making it easy to keep track of many channels simultaneously. The phrase “police scanner” derives from the fact that the …
Standing Wave Ratio (SWR) meters are used to measure the standing wave ratio in a communications transmission line. The meter can display how much a transmission line and the load are mismatched (normally a radio antenna). It also determines how effective the impedance is of matching efforts. In CB and ham radio circles, the SWR …