05-17-2023-0111 - CRM 114 Discriminator, etc. (draft)

The CRM 114 Discriminator is a fictional piece of radio equipment in Stanley Kubrick's film Dr. Strangelove (1964), the destruction of which prevents the crew of a B-52 from receiving the recall code that would stop them from dropping their hydrogen bombs on the Soviet Union. The device is one of several that malfunction in the film, along with Mandrake's telephone call attempts, the bomb doors failing to open and the Doomsday Weapon's misuse, a common theme in Kubrick's work of the failure of human planning.^[1]

The code became a running joke, in Kubrick's work and outside.^[1] Kubrick used a near homophone of "CRM 114", "Serum 114", for the name of a drug injected into Alex to help his reformation in A Clockwork Orange (1971).^[2] In the movie Eyes Wide Shut (1999), the morgue Bill visits is stationed in the hospital's corridor C, Room 114 (CRM 114). 

https://en.wikipedia.org/wiki/CRM_114_(fictional_device)

Crossband (cross-band, cross band) operation is a method of telecommunication in which a radio station receives signals on one frequency and simultaneously transmits on another for the purpose of full duplex communication or signal relay.^[1]

To avoid interference within the equipment at the station, the two frequencies used need to be separated, and ideally on different 'bands'. An unattended station working in this way is a radio repeater. It re-transmits the same information that it receives. This principle is used by telecommunications satellites and terrestrial mobile radio systems. 

https://en.wikipedia.org/wiki/Crossband_operation

In radio, and wireless communications in general, blocking is a condition in a receiver in which an off-frequency signal (generally further off-frequency than the immediately adjacent channel) causes the signal of interest to be suppressed.^[1]

Blocking rejection is the ability of a receiver to tolerate an off-frequency signal and avoid blocking. A good automatic gain control design is part of achieving good blocking rejection.^[2] 

https://en.wikipedia.org/wiki/Blocking_(radio)

A cable grommet is a tube or ring through which an electrical cable passes. They are usually made of rubber or metal.^[1]

The grommet is usually inserted in holes in certain materials in order to protect, improve friction or seal cables passing through it, from a possible mechanical or chemical attack. 

https://en.wikipedia.org/wiki/Cable_grommet

Carrier current transmission, originally called wired wireless, employs guided low-power radio-frequency signals, which are transmitted along electrical conductors. The transmissions are picked up by receivers that are either connected to the conductors, or a short distance from them. Carrier current transmission is used to send audio and telemetry to selected locations, and also for low-power broadcasting that covers a small geographical area, such as a college campus. The most common form of carrier current uses longwave or medium wave AM radio signals that are sent through existing electrical wiring, although other conductors can be used, such as telephone lines.  

https://en.wikipedia.org/wiki/Carrier_current

Chirp transmitter

A chirp transmitter is a shortwave radio transmitter that sweeps the HF radio spectrum on a regular schedule. If one is monitoring a specific frequency, then a chirp is heard (in CW or SSB mode) when the signal passes through. In addition to their use in probing ionospheric properties,^[2] these transmitters are also used for over-the-horizon radar systems.^[3]

An analysis of existing transmitters has been done using SDR technology.^[4] For better identification of chirp transmitters the following notation is used: <repetition rate (s)>:<chirp offset (s)>, where the repetition rate is the time between two sweeps in seconds and the chirp offset is the time of the first sweep from 0 MHz after a full hour in seconds. If the initial frequency is greater than 0 MHz, the offset time can be linearly extrapolated to 0 MHz.^[2] 

https://en.wikipedia.org/wiki/Ionosonde#Chirp_transmitter

In electrical engineering, a circulator is a passive, non-reciprocal three- or four-port device that only allows a microwave or radio-frequency signal to exit through the port directly after the one it entered. Optical circulators have similar behavior. Ports are where an external waveguide or transmission line, such as a microstrip line or a coaxial cable, connects to the device. For a three-port circulator, a signal applied to port 1 only comes out of port 2; a signal applied to port 2 only comes out of port 3; a signal applied to port 3 only comes out of port 1, and so on. An ideal three-port circulator has the following scattering matrix:

${\displaystyle S=\left(\begin{array}{ccc}0& 0& 1\\ 1& 0& 0\\ 0& 1& 0\end{array}\right)}$

 

 

ANSI and IEC standard schematic symbol for a circulator (with each waveguide or transmission line port drawn as a single line, rather than as a pair of conductors)

https://en.wikipedia.org/wiki/Circulator

A cognitive radio (CR) is a radio that can be programmed and configured dynamically to use the best wireless channels in its vicinity to avoid user interference and congestion. Such a radio automatically detects available channels in wireless spectrum, then accordingly changes its transmission or reception parameters to allow more concurrent wireless communications in a given spectrum band at one location. This process is a form of dynamic spectrum management.  

https://en.wikipedia.org/wiki/Cognitive_radio

Comfort noise (or comfort tone) is synthetic background noise used in radio and wireless communications to fill the artificial silence in a transmission resulting from voice activity detection or from the audio clarity of modern digital lines.^[1]

Some modern telephone systems (such as wireless and VoIP) use voice activity detection (VAD), a form of squelching where low volume levels are ignored by the transmitting device. In digital audio transmissions, this saves bandwidth of the communications channel by transmitting nothing when the source volume is under a certain threshold, leaving only louder sounds (such as the speaker's voice) to be sent. However, improvements in background noise reduction technologies can occasionally result in the complete removal of all noise. Although maximizing call quality is of primary importance, exhaustive removal of noise may not properly simulate the typical behavior of terminals on the PSTN system.

The result of receiving total silence, especially for a prolonged period, has a number of unwanted effects on the listener, including the following:

• the listener may believe that the transmission has been lost, and therefore hang up prematurely.
• the speech may sound "choppy" (see noise gate) and difficult to understand.
• the sudden change in sound level can be jarring to the listener.

To counteract these effects, comfort noise is added, usually on the receiving end in wireless or VoIP systems, to fill in the silent portions of transmissions with artificial noise. The noise generated is at a low but audible volume level, and can vary based on the average volume level of received signals to minimize jarring transitions.^[2]

In many VoIP products, users may control how VAD and comfort noise are configured, or disable the feature entirely.^[1]

As part of the RTP audio video profile, RFC 3389 defines a standard for distributing comfort noise information in VoIP systems.

A similar concept is that of sidetone, the effect of sound that is picked up by a telephone's mouthpiece and introduced (at low level) into the earpiece of the same handset, acting as feedback.

During the siege of Leningrad, the beat of a metronome was used as comfort noise on the Leningrad radio network, indicating that the network was still functioning.^[3]

Many radio stations broadcast birdsong, city-traffic or other atmospheric comfort noise during periods of deliberate silence. For example, in the UK, silence is observed on Remembrance Sunday, and London's quiet city ambiance is used. This is to reassure the listener that the station is on-air, but primarily to prevent silence detection systems at transmitters from automatically starting backup tapes of music (designed to be broadcast in the case of transmission link failure).^[4]

See also

• Ambient noise
• Talkspurt
• Discontinuous transmission (DTX)
• Presence (sound recording)
• Autonomous sensory meridian response
• Sound masking
• Dead air

References

1. 
   

"Troubleshooting Hissing and Static: Comfort Noise and VAD". www.cisco.com/. CISCO. Retrieved 18 July 2014.

Suppapola, Seth; Ebenezer, Samuel Ponvara; Allen, Justin L. "Patent US7649988, Comfort noise generator using modified Doblinger noise estimate". www.google.com/patents. USPTO. Retrieved 18 July 2014.

Encyclopaedia of St. Petersburg

4. "RB-SD1 Silence Detect Unit". Sonifex. Retrieved 2013-05-28.

• Gao Research - VAD/CNG
• Newton, Harry. Newton's Telecom Dictionary. 20th ed. 2004.

Categories:

• Noise
• Radio technology
• Voice over IP
• Mobile telecommunications

 https://en.wikipedia.org/wiki/Comfort_noise

Connectivity exchange (CONEX): In an adaptive or manually operated high-frequency (HF) radio network, the automatic or manual exchange of information concerning routes to stations that are not directly reachable by the exchange originator.

The purpose of the exchange is to identify indirect paths and/or possible relay stations to those stations that are not directly reachable.^[1] 

https://en.wikipedia.org/wiki/Connectivity_exchange

In telecommunications, Continuous Tone-Coded Squelch System or CTCSS is one type of in-band signaling that is used to reduce the annoyance of listening to other users on a shared two-way radio communication channel. It is sometimes referred to as tone squelch. It does this by adding a low frequency audio tone to the voice. Where more than one group of users is on the same radio frequency (called co-channel users), CTCSS circuitry mutes those users who are using a different CTCSS tone or no CTCSS. It is sometimes referred to as a sub-channel, but this is a misnomer because no additional channels are created. All users with different CTCSS tones on the same channel are still transmitting on the identical radio frequency, and their transmissions interfere with each other; however; the interference is masked under most conditions. The CTCSS feature also does not offer any security.

A receiver with just a carrier or noise squelch does not suppress any sufficiently strong signal; in CTCSS mode it unmutes only when the signal also carries the correct sub-audible audio tone. The tones are not actually below the range of human hearing, but are poorly reproduced by most communications-grade speakers and in any event are usually filtered out before being sent to the speaker or headphone.

Theory of operation

Radio transmitters using CTCSS always transmit their own tone code whenever the transmit button is pressed. The tone is transmitted at a low level simultaneously with the voice. This is called CTCSS encoding. CTCSS tones range from 67 to 257 Hz. The tones are usually referred to as sub-audible tones. In an FM two-way radio system, CTCSS encoder levels are usually set for 15% of system deviation. For example, in a 5 kHz deviation system, the CTCSS tone level would normally be set to 750 Hz deviation. Engineered systems may call for different level settings in the 500 Hz to 1 kHz (10–20%) range.

The ability of a receiver to mute the audio until it detects a carrier with the correct CTCSS tone is called decoding. Receivers are equipped with features to allow the CTCSS "lock" to be disabled. On a base station console, a microphone may have a split push-to-talk button. Pressing one half of the button, (often marked with a speaker icon or the letters "MON", short for "MONitor") disables the CTCSS decoder and reverts the receiver to hearing any signal on the channel. This is called the monitor function. There is sometimes a mechanical interlock: the user must push down and hold the monitor button or the transmit button is locked and cannot be pressed. This interlock option is referred to as compulsory monitor before transmit (the user is forced to monitor by the hardware design of the equipment itself). On mobile radios, the microphone is usually stored in a hang-up clip or a hang-up box containing a microphone clip. When the user pulls the microphone out of the hang-up clip to make a call, a switch in the clip (box) forces the receiver to revert to conventional carrier squelch mode ("monitor"). Some designs relocate the switch into the body of the microphone itself. In hand-held radios, an LED indicator may glow green, yellow, or orange to indicate another user is talking on the channel. Hand-held radios usually have a switch or push-button to monitor. Some modern radios have a feature called "Busy Channel Lockout", which will not allow the user to transmit as long as the radio is receiving another signal.

A CTCSS decoder is based on a very narrow bandpass filter which passes the desired CTCSS tone. The filter's output is amplified and rectified, creating a DC voltage whenever the desired tone is present. The DC voltage is used to turn on, enable or unmute the receiver's speaker audio stages. When the tone is present, the receiver is unmuted, when it is not present the receiver is silent.

Because period is the inverse of frequency, lower tone frequencies can take longer to decode (depends on the decoder design). Receivers in a system using 67.0 Hz can take noticeably longer to decode than ones using 203.5 Hz, and they can take longer than one decoding 250.3 Hz. In some repeater systems, the time lag can be significant. The lower tone may cause one or two syllables to be clipped before the receiver audio is unmuted (is heard). This is because receivers are decoding in a chain. The repeater receiver must first sense the carrier signal on the input, then decode the CTCSS tone. When that occurs, the system transmitter turns on, encoding the CTCSS tone on its carrier signal (the output frequency). All radios in the system start decoding after they sense a carrier signal then recognize the tone on the carrier as valid. Any distortion on the encoded tone will also affect the decoding time.

Engineered systems often use tones in the 127.3 Hz to 162.2 Hz range to balance fast decoding with keeping the tones out of the audible part of the receive audio. Most amateur radio repeater controller manufacturers offer an audio delay option—this delays the repeated speech audio for a selectable number of milliseconds before it is retransmitted. During this fixed delay period (the amount of which is adjusted during installation, then locked down), the CTCSS decoder has enough time to recognize the right tone. This way the problem with lost syllables at the beginning of a transmission can be overcome without having to use higher frequency tones.

In early systems, it was common to avoid the use of adjacent tones. On channels where every available tone is not in use, this is good engineering practice. For example, an ideal would be to avoid using 97.4 Hz and 100.0 Hz on the same channel. The tones are so close that some decoders may periodically false trigger. The user occasionally hears a syllable or two of co-channel users on a different CTCSS tone talking. As electronic components age, or through production variances, some radios in a system may be better than others at rejecting nearby tone frequencies.

Digital-Coded Squelch

Main article: Squelch § DCS

CTCSS is an analog system. A later Digital-Coded Squelch (DCS) system was developed by Motorola under the trademarked name Digital Private Line (DPL). General Electric responded with the same system under the name of Digital Channel Guard (DCG). The generic name is CDCSS (Continuous Digital-Coded Squelch System). The use of digital squelch on a channel that has existing tone squelch users precludes the use of the 131.8 and 136.5 Hz tones as the digital bit rate is 134.4 bits per second and the decoders set to those two tones will sense an intermittent signal (referred to in the two-way radio field as "falsing" the decoder).^[1]

List of tones

CTCSS tones

NS [1]	PL	Hz	Notes
1	XZ	67.0
39	WZ	69.3	[2]
2	XA	71.9
3	WA	74.4
4	XB	77.0
5	WB	79.7	[3]
6	YZ	82.5
7	YA	85.4
8	YB	88.5
9	ZZ	91.5
10	ZA	94.8
11	ZB	97.4	[4]
12	1Z	100.0
13	1A	103.5
14	1B	107.2
15	2Z	110.9
16	2A	114.8
17	2B	118.8
18	3Z	123.0
19	3A	127.3
20	3B	131.8
21	4Z	136.5
22	4A	141.3
23	4B	146.2
NATO		150.0	[5][7]
24	5Z	151.4
25	5A	156.7
40		159.8	[7]
26	5B	162.2
41		165.5	[7]
27	6Z	167.9
42		171.3	[7]
28	6A	173.8
43		177.3	[7]
29	6B	179.9
44		183.5	[7]
30	7Z	186.2
45		189.9	[7]
31	7A	192.8
46		196.6	[7]
47		199.5	[7]
32	M1	203.5
48	8Z	206.5	[6][7]
33	M2	210.7
34	M3	218.1
35	M4	225.7
49	9Z	229.1	[6][7]
36	M5	233.6
37	M6	241.8
38	M7	250.3
50	0Z	254.1	[6][7]

CTCSS tones are standardized by the EIA/TIA. The full list of the tones can be found in their original standard RS-220A,^[2] and the most recent EIA/TIA-603-E;^[3] the CTCSS tones also may be listed in manufacturers instruction, maintenance or operational manuals. Some systems use non-standard tones.^[4] The NATO Military radios use 150.0 Hz, and this can be found in the user manuals for the radios. Some areas do not use certain tones. For example, the tone of 100.0 Hz is avoided in the United Kingdom since this is twice the UK mains power line frequency; an inadequately smoothed power supply may cause unwanted squelch opening (this is true in many other areas that use 50 Hz power). Tones typically come from one of three series as listed below along with the two character PL code used by Motorola to identify tones. The most common set of supported tones is a set of 39 tones including all tones with Motorola PL codes, except for the tones 8Z, 9Z, and 0Z (zero-Z).^[5] The lowest series has adjacent tones that are roughly in the harmonic ratio of 2^0.05 to 1 (≈1.035265), while the other two series have adjacent tones roughly in the ratio of 10^0.015 to 1 (≈1.035142). An example technical description can be found in a Philips technical information sheet about their CTCSS products.^[6]

Notes

• ¹ Non-standard numerical codes. Many radios use a matching set of numerical codes to represent corresponding tones; however, there is no published standard and only partial industry adoption.
• ² Some radios use 69.4 Hz instead, which better fits the harmonic sequence, and this tone is often omitted as a choice.
• ³ Also known by the code SP.
• ⁴ Not actually in this harmonic sequence, but an average of the ZA and 1Z tones used to fill the gap between the lower and middle sequences. 98.1 Hz would be the tone after ZA, and the tone before 1Z would be 96.6 Hz, assuming the same harmonics were used.
• ⁵ Many NATO military radios have a switchable 150.0 Hz tone. The list includes the following radios: AN/PRC-68, AN/PRC-117F, AN/PRC-117G, AN/PRC-77, AN/PRC-113, AN/PRC-137, AN/PRC-139, AN/PRC-152, AN/PRC-119, AN/VRC-12, AN/PSC-5, and Thales AN/PRC-148 MBITR.
• ⁶ The 8Z, 9Z, and 0Z ("zero-Z") tones are often omitted from radios that use the M1–M7 series of tones.
• ⁷ Non-standard tone not included in current TIA-603-E.

Reverse CTCSS

Some professional systems use a phase-reversal of the CTCSS tone at the end of a transmission to eliminate the squelch crash or squelch tail. This is common with General Electric Mobile Radio and Motorola systems. When the user releases the push-to-talk button the CTCSS tone does a phase shift for about 200 milliseconds. In older systems, the tone decoders used mechanical reeds to decode CTCSS tones. When audio at a resonant pitch was fed into the reed, it would resonate, which would turn on the speaker audio. The end-of-transmission phase reversal (called "Reverse Burst" by Motorola (and trademarked by them) and "Squelch Tail Elimination" or "STE" by GE ^[7]) caused the reed to abruptly stop vibrating which would cause the receive audio to instantly mute. Initially, a phase shift of 180 degrees was used, but experience showed that a shift of ±120 to 135 degrees was optimal in halting the mechanical reeds. These systems often have audio muting logic set for CTCSS only. If a transmitter without the phase reversal feature is used, the squelch can remain unmuted for as long as the reed continues to vibrate—up to 1.5 seconds at the end of a transmission as it coasts to a stop (sometimes referred to as the "flywheel effect" or called "freewheeling").

Interference and CTCSS

In non-critical uses, CTCSS can also be used to hide the presence of interfering signals such as receiver-produced intermodulation. Receivers with poor specifications—such as scanners or low-cost mobile radios—cannot reject the strong signals present in urban environments. The interference will still be present and may block the receiver, but the decoder will prevent it from being heard. It will still degrade system performance but the user will not have to hear the noises produced by receiving the interference.

CTCSS is commonly used in VHF and UHF amateur radio operations for this purpose. Wideband and extremely sensitive radios are common in the amateur radio field, which imposes limits on achievable intermodulation and adjacent-channel performance.^[8]

Family Radio Service (FRS), PMR446 and other consumer-grade radios often include a feature called "Interference Eliminator Codes", "sub-channels", or "privacy codes". These do not afford privacy or security, but serve only to reduce annoying interference by other users or other noise sources; a receiver with the tone squelch turned off will hear everything on the channel.^[9] GMRS/FRS radios offering CTCSS codes typically provide a choice of 38 tones, but the tone number and the tone frequencies used may vary from one manufacturer to another (or even within product lines of one manufacturer) and should not be assumed to be consistent (i.e. "Tone 12" in one set of radios may not be "Tone 12" in another).^[10]

See also

• Radiotelephony procedure
• Signaling (telecommunications)

References

1. 
   

Morris, Mike (2013-01-29). "A Historical and Technical Overview of Tone Squelch Systems". Retrieved 2013-03-06.

EIA Standard RS-220-A, Continuous Tone-Controlled Squelch Systems (CTCSS). March 1979.

Land Mobile FM or PM – Communications Equipment – Measurement and Performance Standards, TIA-603-E (Technical report). Telecommunications Industry Association. March 2, 2016. p. 10.

List of non-standard CTCSS codes

"CTCSS Compatibility in FRS Radios". Archived from the original on 2001-09-24.

"Information Sheet: Continuous Tone Controlled Squelch System" (PDF). Retrieved 2019-07-08.

Explanation of Reverse Burst & "And Squelch" Archived 2008-01-19 at the Wayback Machine - Kevin K. Custer W3KKC

Wilson, Mark J., ed. (2007). The ARRL Operating Manual for Radio Amateurs. American Radio Relay League. pp. 2-12–2-13. ISBN 0872591093.

Silver, H. Ward (2011). Two-Way Radios and Scanners for Dummies. John Wiley & Sons. pp. 62–64. ISBN 1118054601.

10. Eisner, Robert H. (1999-07-23). "CTCSS Compatibility in FRS Radios". Archived from the original on 2014-09-27. Retrieved 2023-01-23.

v t e Two-way radio
Amateur and hobbyist	Amateur radio Amateur radio repeater Citizens band radio Family Radio Service Public Radio Service General Mobile Radio Service KDR 444 LPD433 Mobile rig Multi-Use Radio Service PMR446 UHF CB (Australia)
Aviation (aeronautical mobile)	Air traffic control Aircraft emergency frequency Airband Common traffic advisory frequency Mandatory frequency airport MULTICOM Single Frequency Approach UNICOM
Land-based commercial and government mobile	Base station Business band Mobile radio Professional mobile radio Radio repeater Specialized Mobile Radio Trunked radio system Walkie-talkie
Marine (shipboard)	2182 kHz 500 kHz Coast radio station Marine VHF radio Maritime mobile amateur radio
Signaling / Selective calling	CTCSS D-STAR Dual-tone multi-frequency MDC-1200 Push-to-talk Quik-Call I Quik-Call II Selcall SELCAL
System elements and principles	Antenna APRS Automatic vehicle location Call sign CAD DC remote Dispatch Dynamic range compression Fade margin Link budget Rayleigh fading Tone remote Radiotelephony procedure Voting (diversity combining)

Categories:

• Radio technology
• Telecommunication protocols

 https://en.wikipedia.org/wiki/Continuous_Tone-Coded_Squelch_System

In telecommunication, receive-after-transmit time delay is the time interval between (a) the instant of keying off the local transmitter to stop transmitting and (b) the instant the local receiver output has increased to 90% of its steady-state value in response to an RF (radio-frequency) signal from another transmitter.

The RF signal from the distant transmitter must exist at the local receiver input prior to, or at the time of, keying off the local transmitter.

Receive-after-transmit time delay applies only to half-duplex operation. 

https://en.wikipedia.org/wiki/Receive-after-transmit_time_delay

Radiophysics (also modern writing "radio physics"^[1]) is a branch of physics focused on the theoretical and experimental study of certain kinds of radiation, its emission, propagation and interaction with matter.

The term is used in the following major meanings:

• study of radio waves (the original area of research)
• study of radiation used in radiology^[2]
• study of other ranges of the spectrum of electromagnetic radiation in some specific applications

Among the main applications of radiophysics are radio communications, radiolocation, radio astronomy and radiology.

Branches

• Classical radiophysics deals with radio wave communications and detection
• Quantum radiophysics (physics of lasers and masers; Nikolai Basov was the founder of quantum radiophysics in the Soviet Union)
• Statistical radiophysics

 https://en.wikipedia.org/wiki/Radiophysics

RadioDNS is an organisation that promotes the use of open technology standards to enable hybrid radio. Hybrid radio combines broadcast radio and internet (IP) technologies to create a harmonised distribution technology.

The core technology standard (ETSI TS 103 270) relies on the Domain Name System (DNS) to allow a connected radio receiver to look up IP resources based on their broadcast parameters, such as the station identifier received within the broadcast signal. RadioDNS operates the root name server for the radiodns.org domain according to a published trust model.^[1] Although RadioDNS reserves the right to charge a small annual registration fee of USD10, this has never been charged and continues to be waived.^[2]

The project is an open standard, initially created by a series of broadcasters and manufacturers.^[3] 

https://en.wikipedia.org/wiki/RadioDNS

Radio-frequency welding, also known as dielectric welding and high-frequency welding, is a plastic welding process that utilizes high-frequency electric fields to induce heating and melting of thermoplastic base materials.^[1] The electric field is applied by a pair of electrodes after the parts being joined are clamped together. The clamping force is maintained until the joint solidifies. Advantages of this process are fast cycle times (on the order of a few seconds), automation, repeatability, and good weld appearance. Only plastics which have dipoles can be heated using radio waves and therefore not all plastics are able to be welded using this process. Also, this process is not well suited for thick or overly complex joints. The most common use of this process is lap joints or seals on thin plastic sheets or parts. 

https://en.wikipedia.org/wiki/Radio-frequency_welding

The Magneto Inductive Remote Activation Munition System (MI-RAMS) is a variant of the Remote Munition System (RAMS) that uses electromagnetic induction to control electronic equipment, including demolition charges, munitions, and active barriers.^[1] The handheld MI-RAMS receiver consists of a box-shaped device with a fixed bulkhead-style receptacle connector on the top with a non-leaking metal shell threaded in the rear section of the connector and sealed with an O-ring.^[2]

With the use of quasi-static AC magnetic fields, MI-RAMS is capable of sending signals through ice, rock, soil, water, and concrete. As a result, MI-RAMS is often used to remotely control ordnance items and communication systems in areas in which radio frequency devices under-perform or fail.^[3] These areas include caves, bunkers, tunnels, dense jungle, ice fields, urban structures, and up to 66 feet underwater.^[2][4] The wireless channel created by MI-RAMS does not produce any far field (RF) emissions, which decreases likelihood of detection outside of the operating area.^[3] The MI-RAMS transmitters and receivers have also been designed to work with existing communication technology, allowing other types of handsets to link to the system and communicate with each other as long as one MI-RAMS unit is present.^[5]

MI-RAMS was designed and modified by researchers at the Army Research Laboratory for U.S. Army Combat Engineer Forces and Army and Navy Special Operations Forces (SEALs) to aid in establishing terrain dominance.^[1][6]

^{https://en.wikipedia.org/wiki/Magneto_Inductive_Remote_Activation_Munition_System}

From Wikipedia, the free encyclopedia

This article is about the radiation. For the generic oscillation, see Radio frequency. For the electronics, see Radio frequency engineering. For the British broadcasting station, see Radio Wave 96.5. For other uses, see Radio Waves.

Animation of a half-wave dipole antenna radiating radio waves, showing the electric field lines. The antenna in the center is two vertical metal rods connected to a radio transmitter (not shown). The transmitter applies an alternating electric current to the rods, which charges them alternately positive (+) and negative (−). Loops of electric field leave the antenna and travel away at the speed of light; these are the radio waves. In this animation the action is shown slowed down enormously.

Radio waves are a type of electromagnetic radiation with the longest wavelengths in the electromagnetic spectrum, typically with frequencies of 300 gigahertz (GHz) and below.^{[citation needed]} At 300GHz, the corresponding wavelength is 1mm, which is shorter than a grain of rice. At 30Hz the corresponding wavelength is ~10,000 kilometers (6,200 miles) longer than the radius of the Earth. Like all electromagnetic waves, radio waves in a vacuum travel at the speed of light, and in the Earth's atmosphere at a close, but slightly lower speed. Radio waves are generated by charged particles undergoing acceleration, such as time-varying electric currents.^[1] Naturally occurring radio waves are emitted by lightning and astronomical objects, and are part of the blackbody radiation emitted by all warm objects.

Radio waves are generated artificially by an electronic device called a transmitter, which is connected to an antenna which radiates the waves. They are received by another antenna connected to a radio receiver, which processes the received signal. Radio waves are very widely used in modern technology for fixed and mobile radio communication, broadcasting, radar and radio navigation systems, communications satellites, wireless computer networks and many other applications. Different frequencies of radio waves have different propagation characteristics in the Earth's atmosphere; long waves can diffract around obstacles like mountains and follow the contour of the earth (ground waves), shorter waves can reflect off the ionosphere and return to earth beyond the horizon (skywaves), while much shorter wavelengths bend or diffract very little and travel on a line of sight, so their propagation distances are limited to the visual horizon.

To prevent interference between different users, the artificial generation and use of radio waves is strictly regulated by law, coordinated by an international body called the International Telecommunication Union (ITU), which defines radio waves as "electromagnetic waves of frequencies arbitrarily lower than 3,000 GHz, propagated in space without artificial guide".^[2] The radio spectrum is divided into a number of radio bands on the basis of frequency, allocated to different uses.

Diagram of the electric fields (E) and magnetic fields (H) of radio waves emitted by a monopole radio transmitting antenna (small dark vertical line in the center). The E and H fields are perpendicular, as implied by the phase diagram in the lower right.

Discovery and exploitation

Main article: History of radio

Radio waves were first predicted by the theory of electromagnetism proposed in 1867 by Scottish mathematical physicist James Clerk Maxwell.^[3] His mathematical theory, now called Maxwell's equations, predicted that a coupled electric and magnetic field could travel through space as an "electromagnetic wave". Maxwell proposed that light consisted of electromagnetic waves of very short wavelength. In 1887, German physicist Heinrich Hertz demonstrated the reality of Maxwell's electromagnetic waves by experimentally generating radio waves in his laboratory,^[4] showing that they exhibited the same wave properties as light: standing waves, refraction, diffraction, and polarization. Italian inventor Guglielmo Marconi developed the first practical radio transmitters and receivers around 1894–1895. He received the 1909 Nobel Prize in physics for his radio work. Radio communication began to be used commercially around 1900. The modern term "radio wave" replaced the original name "Hertzian wave" around 1912.

Generation and reception

Animated diagram of a half-wave dipole antenna receiving a radio wave. The antenna consists of two metal rods connected to a receiver R. The electric field (E, green arrows) of the incoming wave pushes the electrons in the rods back and forth, charging the ends alternately positive (+) and negative (−). Since the length of the antenna is one half the wavelength of the wave, the oscillating field induces standing waves of voltage (V, represented by red band) and current in the rods. The oscillating currents (black arrows) flow down the transmission line and through the receiver (represented by the resistance R).

Radio waves are radiated by charged particles when they are accelerated. Natural sources of radio waves include radio noise produced by lightning and other natural processes in the Earth's atmosphere, and astronomical radio sources in space such as the Sun, galaxies and nebulas. All warm objects radiate high frequency radio waves (microwaves) as part of their black body radiation.

Radio waves are produced artificially by time-varying electric currents, consisting of electrons flowing back and forth in a specially-shaped metal conductor called an antenna. An electronic device called a radio transmitter applies oscillating electric current to the antenna, and the antenna radiates the power as radio waves. Radio waves are received by another antenna attached to a radio receiver. When radio waves strike the receiving antenna they push the electrons in the metal back and forth, creating tiny oscillating currents which are detected by the receiver.

From quantum mechanics, like other electromagnetic radiation such as light, radio waves can alternatively be regarded as streams of uncharged elementary particles called photons.^[5] In an antenna transmitting radio waves, the electrons in the antenna emit the energy in discrete packets called radio photons, while in a receiving antenna the electrons absorb the energy as radio photons. An antenna is a coherent emitter of photons, like a laser, so the radio photons are all in phase.^[6][5] However, from Planck's relation ${\displaystyle E=h\nu }$ the energy of individual radio photons is extremely small,^[5] from 10⁻²² to 10⁻³⁰ joules. So the antenna of even a very low power transmitter emits enormous numbers of photons per second. Therefore, except for certain molecular electron transition processes such as atoms in a maser emitting microwave photons, radio wave emission and absorption is usually regarded as a continuous classical process, governed by Maxwell's equations.

Properties

Radio waves in a vacuum travel at the speed of light ${\displaystyle c}$ .^[7][8] When passing through a material medium, they are slowed depending on the medium's permeability and permittivity. Air is thin enough that in the Earth's atmosphere radio waves travel very close to the speed of light.

The wavelength ${\displaystyle \lambda }$ is the distance from one peak (crest) of the wave's electric field to the next, and is inversely proportional to the frequency ${\displaystyle f}$ of the wave. The relation of frequency and wavelength in a radio wave traveling in vacuum or air is

${\displaystyle \lambda =\frac{c}{f},}$

where

${\displaystyle c\approx 299.79\times {10}^6\text{ m/s}.}$

Equivalently, ${\displaystyle c}$ the distance a radio wave travels in a vacuum, in one second, is 299,792,458 meters (983,571,056 ft), which is the wavelength of a 1 hertz radio signal. A 1 megahertz radio wave (mid-AM band) has a wavelength of 299.79 meters (983.6 ft).

Polarization

Like other electromagnetic waves, a radio wave has a property called polarization, which is defined as the direction of the wave's oscillating electric field perpendicular to the direction of motion. A plane polarized radio wave has an electric field which oscillates in a plane along the direction of motion. In a horizontally polarized radio wave the electric field oscillates in a horizontal direction. In a vertically polarized wave the electric field oscillates in a vertical direction. In a circularly polarized wave the electric field at any point rotates about the direction of travel, once per cycle. A right circularly polarized wave rotates in a right hand sense about the direction of travel, while a left circularly polarized wave rotates in the opposite sense. The wave's magnetic field is perpendicular to the electric field, and the electric and magnetic field are oriented in a right hand sense with respect to the direction of radiation.

An antenna emits polarized radio waves, with the polarization determined by the direction of the metal antenna elements. For example a dipole antenna consists of two collinear metal rods. If the rods are horizontal it radiates horizontally polarized radio waves, while if the rods are vertical it radiates vertically polarized waves. An antenna receiving the radio waves must have the same polarization as the transmitting antenna, or it will suffer a severe loss of reception. Many natural sources of radio waves, such as the sun, stars and blackbody radiation from warm objects, emit unpolarized waves, consisting of incoherent short wave trains in an equal mixture of polarization states.

The polarization of radio waves is determined by a quantum mechanical property of the photons called their spin. A photon can have one of two possible values of spin; it can spin in a right hand sense about its direction of motion, or in a left hand sense. Right circularly polarized radio waves consist of photons spinning in a right hand sense. Left circularly polarized radio waves consist of photons spinning in a left hand sense. Plane polarized radio waves consist of photons in a quantum superposition of right and left hand spin states. The electric field consists of a superposition of right and left rotating fields, resulting in a plane oscillation.

Propagation characteristics

Main article: Radio propagation

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Radio waves are more widely used for communication than other electromagnetic waves mainly because of their desirable propagation properties, stemming from their large wavelength.^[9] Radio waves have the ability to pass through the atmosphere in any weather, foliage, and most building materials, and by diffraction can bend around obstructions,^{[clarification needed]} and unlike other electromagnetic waves they tend to be scattered rather than absorbed by objects larger than their wavelength.

The study of radio propagation, how radio waves move in free space and over the surface of the Earth, is vitally important in the design of practical radio systems. Radio waves passing through different environments experience reflection, refraction, polarization, diffraction, and absorption. Different frequencies experience different combinations of these phenomena in the Earth's atmosphere, making certain radio bands more useful for specific purposes than others. Practical radio systems mainly use three different techniques of radio propagation to communicate:^[10]

• Line of sight: This refers to radio waves that travel in a straight line from the transmitting antenna to the receiving antenna. It does not necessarily require a cleared sight path; at lower frequencies radio waves can pass through buildings, foliage and other obstructions. This is the only method of propagation possible at frequencies above 30 MHz. On the surface of the Earth, line of sight propagation is limited by the visual horizon to about 64 km (40 mi). This is the method used by cell phones, FM, television broadcasting and radar. By using dish antennas to transmit beams of microwaves, point-to-point microwave relay links transmit telephone and television signals over long distances up to the visual horizon. Ground stations can communicate with satellites and spacecraft billions of miles from Earth.
  • Indirect propagation: Radio waves can reach points beyond the line-of-sight by diffraction and reflection.^[10] Diffraction causes radio waves to bend around obstructions such as a building edge, a vehicle, or a turn in a hall. Radio waves also partially reflect from surfaces such as walls, floors, ceilings, vehicles and the ground. These propagation methods occur in short range radio communication systems such as cell phones, cordless phones, walkie-talkies, and wireless networks. A drawback of this mode is multipath propagation, in which radio waves travel from the transmitting to the receiving antenna via multiple paths. The waves interfere, often causing fading and other reception problems.
• Ground waves: At lower frequencies below 2 MHz, in the medium wave and longwave bands, due to diffraction vertically polarized radio waves can bend over hills and mountains, and propagate beyond the horizon, traveling as surface waves which follow the contour of the Earth. This makes it possible for mediumwave and longwave broadcasting stations to have coverage areas beyond the horizon, out to hundreds of miles. As the frequency drops, the losses decrease and the achievable range increases. Military very low frequency (VLF) and extremely low frequency (ELF) communication systems can communicate over most of the Earth. VLF and ELF radio waves can also penetrate water to hundreds of meters depth, so they are used to communicate with submerged submarines.
• Skywaves: At medium wave and shortwave wavelengths, radio waves reflect off conductive layers of charged particles (ions) in a part of the atmosphere called the ionosphere. So radio waves directed at an angle into the sky can return to Earth beyond the horizon; this is called "skip" or "skywave" propagation. By using multiple skips communication at intercontinental distances can be achieved. Skywave propagation is variable and dependent on atmospheric conditions; it is most reliable at night and in the winter. Widely used during the first half of the 20th century, due to its unreliability skywave communication has mostly been abandoned. Remaining uses are by military over-the-horizon (OTH) radar systems, by some automated systems, by radio amateurs, and by shortwave broadcasting stations to broadcast to other countries.

At microwave frequencies, atmospheric gases begin absorbing radio waves, so the range of practical radio communication systems decreases with increasing frequency. Below about 20 GHz atmospheric attenuation is mainly due to water vapor. Above 20 GHz, in the millimeter wave band, other atmospheric gases begin to absorb the waves, limiting practical transmission distances to a kilometer or less. Above 300 GHz, in the terahertz band, virtually all the power is absorbed within a few meters, so the atmosphere is effectively opaque.^[11][12]

Radio communication

Main article: Radio

In radio communication systems, information is transported across space using radio waves. At the sending end, the information to be sent, in the form of a time-varying electrical signal, is applied to a radio transmitter.^[13] The information, called the modulation signal, can be an audio signal representing sound from a microphone, a video signal representing moving images from a video camera, or a digital signal representing data from a computer. In the transmitter, an electronic oscillator generates an alternating current oscillating at a radio frequency, called the carrier wave because it creates the radio waves that "carry" the information through the air. The information signal is used to modulate the carrier, altering some aspect of it, "piggybacking" the information on the carrier. The modulated carrier is amplified and applied to an antenna. The oscillating current pushes the electrons in the antenna back and forth, creating oscillating electric and magnetic fields, which radiate the energy away from the antenna as radio waves. The radio waves carry the information to the receiver location.

At the receiver, the oscillating electric and magnetic fields of the incoming radio wave push the electrons in the receiving antenna back and forth, creating a tiny oscillating voltage which is a weaker replica of the current in the transmitting antenna.^[13] This voltage is applied to the radio receiver, which extracts the information signal. The receiver first uses a bandpass filter to separate the desired radio station's radio signal from all the other radio signals picked up by the antenna, then amplifies the signal so it is stronger, then finally extracts the information-bearing modulation signal in a demodulator. The recovered signal is sent to a loudspeaker or earphone to produce sound, or a television display screen to produce a visible image, or other devices. A digital data signal is applied to a computer or microprocessor, which interacts with a human user.

The radio waves from many transmitters pass through the air simultaneously without interfering with each other. They can be separated in the receiver because each transmitter's radio waves oscillate at a different rate, in other words each transmitter has a different frequency, measured in kilohertz (kHz), megahertz (MHz) or gigahertz (GHz). The bandpass filter in the receiver consists of a tuned circuit which acts like a resonator, similarly to a tuning fork.^[13] It has a natural resonant frequency at which it oscillates. The resonant frequency is set equal to the frequency of the desired radio station. The oscillating radio signal from the desired station causes the tuned circuit to oscillate in sympathy, and it passes the signal on to the rest of the receiver. Radio signals at other frequencies are blocked by the tuned circuit and not passed on.

Biological and environmental effects

Radio waves are non-ionizing radiation, which means they do not have enough energy to separate electrons from atoms or molecules, ionizing them, or break chemical bonds, causing chemical reactions or DNA damage. The main effect of absorption of radio waves by materials is to heat them, similarly to the infrared waves radiated by sources of heat such as a space heater or wood fire. The oscillating electric field of the wave causes polar molecules to vibrate back and forth, increasing the temperature; this is how a microwave oven cooks food. However, unlike infrared waves, which are mainly absorbed at the surface of objects and cause surface heating, radio waves are able to penetrate the surface and deposit their energy inside materials and biological tissues. The depth to which radio waves penetrate decreases with their frequency, and also depends on the material's resistivity and permittivity; it is given by a parameter called the skin depth of the material, which is the depth within which 63% of the energy is deposited. For example, the 2.45 GHz radio waves (microwaves) in a microwave oven penetrate most foods approximately 2.5 to 3.8 cm (1 to 1.5 inches). Radio waves have been applied to the body for 100 years in the medical therapy of diathermy for deep heating of body tissue, to promote increased blood flow and healing. More recently they have been used to create higher temperatures in hyperthermia treatment and to kill cancer cells. Looking into a source of radio waves at close range, such as the waveguide of a working radio transmitter, can cause damage to the lens of the eye by heating. A strong enough beam of radio waves can penetrate the eye and heat the lens enough to cause cataracts.^{[14][15][16][17][18]}

Since the heating effect is in principle no different from other sources of heat, most research into possible health hazards of exposure to radio waves has focused on "nonthermal" effects; whether radio waves have any effect on tissues besides that caused by heating. Radiofrequency electromagnetic fields have been classified by the International Agency for Research on Cancer (IARC) as having "limited evidence" for its effects on humans and animals.^[19][20] There is weak mechanistic evidence of cancer risk via personal exposure to RF-EMF from mobile telephones.^[21]

Radio waves can be shielded against by a conductive metal sheet or screen, an enclosure of sheet or screen is called a Faraday cage. A metal screen shields against radio waves as well as a solid sheet as long as the holes in the screen are smaller than about 1⁄20 of wavelength of the waves.^[22]

Measurement

Since radio frequency radiation has both an electric and a magnetic component, it is often convenient to express intensity of radiation field in terms of units specific to each component. The unit volts per meter (V/m) is used for the electric component, and the unit amperes per meter (A/m) is used for the magnetic component. One can speak of an electromagnetic field, and these units are used to provide information about the levels of electric and magnetic field strength at a measurement location.

Another commonly used unit for characterizing an RF electromagnetic field is power density. Power density is most accurately used when the point of measurement is far enough away from the RF emitter to be located in what is referred to as the far field zone of the radiation pattern.^[23] In closer proximity to the transmitter, i.e., in the "near field" zone, the physical relationships between the electric and magnetic components of the field can be complex, and it is best to use the field strength units discussed above. Power density is measured in terms of power per unit area, for example, milliwatts per square centimeter (mW/cm²). When speaking of frequencies in the microwave range and higher, power density is usually used to express intensity since exposures that might occur would likely be in the far field zone.

See also

• Radio astronomy
• Television transmitter

References

1. 
   

Ellingson, Steven W. (2016). Radio Systems Engineering. Cambridge University Press. pp. 16–17. ISBN 978-1316785164.

"Ch. 1: Terminology and technical characteristics - Terms and definitions". Radio Regulations (PDF). Geneva, CH: ITU. 2016. p. 7. ISBN 9789261191214.

Harman, Peter Michael (1998). The natural philosophy of James Clerk Maxwell. Cambridge, UK: Cambridge University Press. p. 6. ISBN 0-521-00585-X.

Edwards, Stephen A. "Heinrich Hertz and electromagnetic radiation". American Association for the Advancement of Science. Retrieved 13 April 2021.

Gosling, William (1998). Radio Antennas and Propagation (PDF). Newnes. pp. 2, 12. ISBN 0750637412.

Shore, Bruce W. (2020). Our Changing Views of Photons: A Tutorial Memoir. Oxford University Press. p. 54. ISBN 9780192607645.

"Electromagnetic Frequency, Wavelength and Energy Ultra Calculator". 1728.org. 1728 Software Systems. Retrieved 15 Jan 2018.

"How Radio Waves Are Produced". NRAO. Archived from the original on 28 March 2014. Retrieved 15 Jan 2018.

Ellingson, Steven W. (2016). Radio Systems Engineering. Cambridge University Press. pp. 16–17. ISBN 978-1316785164.

Seybold, John S. (2005). "1.2 Modes of Propagation". Introduction to RF Propagation. John Wiley and Sons. pp. 3–10. ISBN 0471743682.

Coutaz, Jean-Louis; Garet, Frederic; Wallace, Vincent P. (2018). Principles of Terahertz Time-Domain Spectroscopy: An Introductory Textbook. CRC Press. p. 18. ISBN 9781351356367.

Siegel, Peter (2002). "Studying the Energy of the Universe". Education materials. NASA website. Retrieved 19 May 2021.

Brain, M. (7 Dec 2000). "How Radio Works". HowStuffWorks.com. Retrieved 11 Sep 2009.

Kitchen, Ronald (2001). RF and Microwave Radiation Safety Handbook (2nd ed.). Newnes. pp. 64–65. ISBN 0750643552.

van der Vorst, André; Rosen, Arye; Kotsuka, Youji (2006). RF/Microwave Interaction with Biological Tissues. John Wiley & Sons. pp. 121–122. ISBN 0471752045.

Graf, Rudolf F.; Sheets, William (2001). Build Your Own Low-power Transmitters: Projects for the Electronics Experimenter. Newnes. p. 234. ISBN 0750672447.

Elder, Joe Allen; Cahill, Daniel F. (1984). "Biological Effects of RF Radiation". Biological Effects of Radiofrequency Radiation. US EPA. pp. 5.116–5.119.

Hitchcock, R. Timothy; Patterson, Robert M. (1995). Radio-Frequency and ELF Electromagnetic Energies: A handbook for health professionals. Industrial Health and Safety Series. John Wiley & Sons. pp. 177–179. ISBN 9780471284543.

"IARC Classifies Radiofrequency Electromagnetic Fields as Possibly Carcinogenic to Humans" (PDF). www.iarc.fr (Press release). WHO. 31 May 2011. Retrieved 9 Jan 2019.

"Agents Classified by the IARC Monographs". monographs.iarc.fr. Volumes 1–123. IARC. 9 Nov 2018. Retrieved 9 Jan 2019.

Baan, R.; Grosse, Y.; Lauby-Secretan, B.; El Ghissassi, F. (2014). "Radiofrequency Electromagnetic Fields: Evaluation of cancer hazards" (PDF). monographs.iarc.fr (conference poster). IARC. Retrieved 9 Jan 2019.

Kimmel, William D.; Gerke, Daryl (2018). Electromagnetic Compatibility in Medical Equipment: A Guide for Designers and Installers. Routledge. p. 6.67. ISBN 9781351453370.

23. National Association of Broadcasters (1996). Antenna & Tower Regulation Handbook. Science and Technology Department. NAB. p. 186. ISBN 9780893242367. Archived from the original on 1 May 2018.

• Maxwell, James Clerk (1865). "VIII. A Dynamical Theory of the Electromagnetic Field". Philosophical Transactions of the Royal Society of London. 155: 459–512. doi:10.1098/rstl.1865.0008. S2CID 186207827.
• Hertz, Heinrich Rudolph (1893). Electric waves: being researches on the propagation of electric action with finite velocity through space. Cornell University Library. Ithaca, NY: Cornell University. ISBN 9781429740364.
• Rawer, Karl (1993). Wave Propagation in the Ionosphere. Developments in electromagnetic theory and applications series. Dordrecht: Kluwer Academic. ISBN 9780792307754. OCLC 26257685.

External links

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Look up radio wave in Wiktionary, the free dictionary.

• "Radio Waves". Science Mission Directorate. NASA.

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https://en.wikipedia.org/wiki/Radio_wave

A radio transmitter or just transmitter is an electronic device which produces radio waves with an antenna. Radio waves are electromagnetic waves with frequencies between about 30 Hz and 300 GHz. The transmitter itself generates a radio frequency alternating current, which is applied to the antenna. When excited by this alternating current, the antenna radiates radio waves. Transmitters are necessary parts of all systems that use radio: radio and television broadcasting, cell phones, wireless networks, radar, two way radios like walkie talkies, radio navigation systems like GPS, remote entry systems, among numerous other uses.

A transmitter can be a separate piece of equipment, or an electronic circuit within another device. Most transmitters consist of an electronic oscillator which generates an oscillating carrier wave, a modulator which impresses an information bearing modulation signal on the carrier, and an amplifier which increases the power of the signal. To prevent interference between different users of the radio spectrum, transmitters are strictly regulated by national radio laws, and are restricted to certain frequencies and power levels, depending on use. The design must usually be type approved before sale. An important legal requirement is that the circuit does not radiate significant radio wave power outside its assigned frequency band, called spurious emission. 

https://en.wikipedia.org/wiki/Radio_transmitter_design

A radio teleswitch is a device used in the United Kingdom primarily to allow electricity suppliers to switch large numbers of electricity meters between different tariff rates, by broadcasting an embedded signal in broadcast radio signals. Radio teleswitches are also used to switch on/off consumer appliances to make use of cheaper differential tariffs such as Economy 7.  

https://en.wikipedia.org/wiki/Radio_teleswitch

Example of single tube triode grid leak receiver from 1920, the first type of amplifying radio receiver. In the left picture the grid leak resistor and capacitor are labeled.

A grid leak resistor and capacitor unit from 1926. The 2 megohm cartridge resistor is replaceable so the user can try different values. The parallel capacitor is built into the holder.

A grid leak detector is an electronic circuit that demodulates an amplitude modulated alternating current and amplifies the recovered modulating voltage. The circuit utilizes the non-linear cathode to control grid conduction characteristic and the amplification factor of a vacuum tube.^[1][2] Invented by Lee De Forest around 1912, it was used as the detector (demodulator) in the first vacuum tube radio receivers until the 1930s. 

https://en.wikipedia.org/wiki/Grid-leak_detector

The General Mobile Radio Service (GMRS) is a land-mobile FM UHF radio service designed for short-distance two-way communication and authorized under part 95 of 47 USC. It requires a license in the United States, but some GMRS compatible equipment can be used license-free in Canada. The US GMRS license is issued for a period of 10 years by the FCC. The United States permits use by adult individuals who possess a valid GMRS license, as well as their immediate family members.^[a] Immediate relatives of the GMRS system licensee are entitled to communicate among themselves for personal or business^[1] purposes, but employees of the licensee who are not family members are not covered by the license. Non-family members must be licensed separately.

GMRS radios are typically handheld portable devices much like Family Radio Service (FRS) radios, and they share a frequency band with FRS near 462 and 467 MHz. Mobile and base station-style radios are available as well, but these are normally commercial UHF radios as often used in the public service and commercial land mobile bands. These are legal for use in this service as long as they are certified for GMRS under USC 47 Part 95.

GMRS licensees are allowed to establish repeaters to extend their communications range. GMRS repeaters are permitted to be linked with other GMRS repeaters but are not authorized to connect to the public switched telephone network. 

https://en.wikipedia.org/wiki/General_Mobile_Radio_Service

The 800 MHz frequency band is a portion of the electromagnetic spectrum, or frequency band, that encompasses 790–862 MHz.

Being a part of the spectrum known as "UHF Bands IV and V" (i.e. 470 MHz to 862 MHz) it was allocated by the ITU to Broadcasting as the primary user in Region 1 and was used for analogue television broadcasting before changing to digital terrestrial television in many countries.^{[nb 1]} As such it is also referred to as "digital dividend" spectrum. In Europe and to some extent elsewhere, the band corresponds to UHF channel 61–69. In most territories the band was also used by Services Ancillary to Broadcasting (SAB) or Services Ancillary to Programme Making (SAP), both often now referred to as PMSE (Programme Making and Special Events) in the form of professional wireless microphones, radio talkback systems and wireless monitor systems.

The European Parliament approved in May 2010, and Japan in 2012, the change of use of the 800 MHz band making it available for purposes other than broadcasting (television) – e.g. mobile broadband.^[1]

From the year 2013 the 800 MHz band can be used to deliver wireless broadband services, in Europe.^[2] 

https://en.wikipedia.org/wiki/800_MHz_frequency_band

Alternative frequency (or AF) is an option that allows a receiver to re-tune to a different frequency that provides the same station, when the first signal becomes too weak (e.g. when moving out of range). This is often used in car stereo systems, enabled by Radio Data System (RDS), or the U.S.-based Radio Broadcast Data System (RBDS).

https://en.wikipedia.org/wiki/Alternative_frequency

AM stereo is a term given to a series of mutually incompatible techniques for radio broadcasting stereo audio in the AM band in a manner that is compatible with standard AM receivers. There are two main classes of systems: independent sideband (ISB) systems, promoted principally by American broadcast engineer Leonard R. Kahn; and quadrature amplitude modulation (QAM) multiplexing systems (conceptually closer to FM stereo).

Initially adopted by many commercial AM broadcasters in the mid to late 1980s, AM stereo broadcasting soon began to decline due to a lack of receivers (most "AM/FM stereo" radios only receive in stereo on FM), a growing exodus of music broadcasters to FM, concentration of ownership of the few remaining stations in the hands of large corporations and the removal of music from AM stations in favour of news/talk or sports broadcasting. By 2001, most of the former AM stereo broadcasters were no longer stereo or had left the AM band entirely. 

https://en.wikipedia.org/wiki/AM_stereo

Autofahrer-Rundfunk-Informationssystem (ARI, German for: Automotive-Driver's-Broadcasting-Information) was a system for indicating the presence of traffic information in FM broadcasts used by the German ARD network of FM radio stations from 1974.^[1] Developed jointly by IRT and Blaupunkt,^[2] it indicated the presence of traffic announcements through manipulation of the 57kHz subcarrier of the station's FM signal.^[3]

ARI was rendered obsolete by the more modern Radio Data System and the ARD stopped broadcasting ARI signals on March 1, 2005.^[4] 

https://en.wikipedia.org/wiki/Autofahrer-Rundfunk-Informationssystem

The term bandstacked applies to an antenna or satellite feedhorn (LNBF) that is designed to operate on two or more bands of frequencies. Usually, a portion of the radio frequency spectrum that has been divided into a low band and a high band.

This example is for a C Band LNBF that operates with two different local oscillator frequencies.

Model Number B1SAT STACK I/P Frequency 3.7-4.2 GHz O/P Frequency 950-2050 MHz LO Frequency Lower Band 5.15 GHz, Upper Band 5.75 GHz

One application is to send both H and V signals to the receiver on one cable at the same time. Other LNBF are voltage switched by the receiver for V or H signal.

· Extended Frequency 3.7 GHz ~ 4.2 GHz · Bandstacked LNBF

This also can be applied to the design and construction of VHF antennas, typically base station antennas that can cover the VHF low band and high band. This should not be confused with stacked antenna array configurations. 

https://en.wikipedia.org/wiki/Bandstacked

In telecommunications, attack-time delay is the time needed for a receiver or transmitter to respond to an incoming signal.

For a receiver, the attack-time delay is defined as the time interval from the instant a step radio-frequency (RF) signal, at a level equal to the receiver's threshold of sensitivity, is applied to the receiver input, to the instant when the receiver's output amplitude reaches 90% of its steady-state value. If a squelch circuit is operating, the receiver attack-time delay includes the time for the receiver to break squelch.

For a transmitter, the attack-time delay is defined as the interval from the instant the transmitter is keyed-on to the instant the transmitted RF signal amplitude has increased to a specified level, usually 90% of its key-on steady-state value. The transmitter attack-time delay excludes the time required for automatic antenna tuning. 

https://en.wikipedia.org/wiki/Attack-time_delay

Ultra-wideband (UWB, ultra wideband, ultra-wide band and ultraband) is a radio technology that can use a very low energy level for short-range, high-bandwidth communications over a large portion of the radio spectrum.^[1] UWB has traditional applications in non-cooperative radar imaging. Most recent applications target sensor data collection, precise locating,^[2] and tracking.^[3][4][5] UWB support started to appear in high-end smartphones in 2019. 

https://en.wikipedia.org/wiki/Ultra-wideband

Visual radio is a generic term for adding visuals to normal audio radio broadcasts. Visual Radio is also a trademark for a Nokia solution for interactive radio with FM radio over a data connection. 

https://en.wikipedia.org/wiki/Visual_radio

Programme Identification (PI) is a service provided by radio stations transmitting Radio Data System (RDS) data as part of the FM radio broadcast. The PI code allows the radio to identify the station across different broadcast relay stations. This in turn allows listeners to stay tuned to a network whilst travelling across the service area of multiple transmitters.

The PI code is a 4-digit hexadecimal (16-bit) number. For example BBC Radio 1 has PI code C201. (The number itself is usually not displayed on radio receivers.)

PI codes are not globally unique; ranges are assigned per-country, and are re-used in countries beyond FM radio range of each other. For example, the first digit "C" as used in the BBC PI code example is used by the United Kingdom, Lithuania, Croatia, and Malta.^{[1]: 69–72} They can be made globally unique by combining them with an ECC (extended country code).

PI codes are also used in Digital Audio Broadcasting as Station ID, and by the RadioDNS standard. 

https://en.wikipedia.org/wiki/Programme_identification

Pocket FM is a small, low-powered radio transmitter designed for use in areas with tightly controlled or undeveloped communications infrastructure. The devices are portable and have the appearance of a receiver rather than a transmitter, making them more practical for citizen use and harder for authorities to detect when used subversively in pirate radio networks. It was designed by Germany-based non-profit organization Media in Cooperation and Transition (MiCT) in 2013 and has been deployed in Syria to create the radio network called Syrnet.

Development

MiCT led the project as an extension of its work on media projects to empower people in areas of conflict and crisis.^[1][2] The device's design is a result of the organization's collaboration with German design firm IXDS.^[3]

Radio, as an analog medium, is more difficult than Internet and phone networks to shut down, requires less physical infrastructure, and its use is less dependent on a functional electric grid.^[4][5] For these reasons radio is a common medium among resistance and other independent groups.

The early versions' shoebox-sized appearance, as described by The Local, was "a black box about thirty centimeters in length and twenty wide. It is smooth and light with a corrugated surface."^[5] Its design emphasizes portability and an appearance unlike typical transmitters. Version 3, introduced at the Global Media Forum in June 2016, is smaller, measuring 20 x 20 x 13 cm, with an aluminum case. The cost of version 3 at release was €3,000.^[6]

The Pocket FM was a finalist for 2016 Siemens Stiftung Empowering People Award.^[7] 

https://en.wikipedia.org/wiki/Pocket_FM

Diagram showing a possible configuration for a wired-wireless mesh network, connected upstream via a VSAT link (click to enlarge)

A wireless mesh network (WMN) is a communications network made up of radio nodes organized in a mesh topology. It can also be a form of wireless ad hoc network.^[1]

A mesh refers to rich interconnection among devices or nodes. Wireless mesh networks often consist of mesh clients, mesh routers and gateways. Mobility of nodes is less frequent. If nodes constantly or frequently move, the mesh spends more time updating routes than delivering data. In a wireless mesh network, topology tends to be more static, so that routes computation can converge and delivery of data to their destinations can occur. Hence, this is a low-mobility centralized form of wireless ad hoc network. Also, because it sometimes relies on static nodes to act as gateways, it is not a truly all-wireless ad hoc network.^{[citation needed]}

Mesh clients are often laptops, cell phones, and other wireless devices. Mesh routers forward traffic to and from the gateways, which may or may not be connected to the Internet. The coverage area of all radio nodes working as a single network is sometimes called a mesh cloud. Access to this mesh cloud depends on the radio nodes working together to create a radio network. A mesh network is reliable and offers redundancy. When one node can no longer operate, the rest of the nodes can still communicate with each other, directly or through one or more intermediate nodes. Wireless mesh networks can self form and self heal. Wireless mesh networks work with different wireless technologies including 802.11, 802.15, 802.16, cellular technologies and need not be restricted to any one technology or protocol. 

https://en.wikipedia.org/wiki/Wireless_mesh_network

Wunderlich refers to a series of vacuum tubes introduced in the early 1930s. Wunderlichs were designed to be used as full-wave detectors in AM radio receivers. However, because of their unusual design, they were rarely used in commercially manufactured receivers. The tube is named for its inventor, Norman Wunderlich. 

https://en.wikipedia.org/wiki/Wunderlich_(vacuum_tube)

Wireless USB (Universal Serial Bus) was a short-range, high-bandwidth wireless radio communication protocol created by the Wireless USB Promoter Group which intended to increase the availability of general USB-based technologies. It was unrelated to Wi-Fi, and different from the Cypress WirelessUSB offerings. It was maintained by the WiMedia Alliance which ceased operations in 2009. Wireless USB is sometimes abbreviated as "WUSB", although the USB Implementers Forum discouraged this practice and instead prefers to call the technology Certified Wireless USB to distinguish it from the competing UWB standard.

Wireless USB was based on the (now defunct) WiMedia Alliance's Ultra-WideBand (UWB) common radio platform, which is capable of sending 480 Mbit/s at distances up to 3 metres (9.8 ft) and 110 Mbit/s at up to 10 metres (33 ft). It was designed to operate in the 3.1 to 10.6 GHz frequency range, although local regulatory policies may restrict the legal operating range in some countries.

The standard is now obsolete, and no new hardware has been produced for many years.^{[citation needed]}

Support for the standard was deprecated in Linux 5.4^[1][2] and removed in Linux 5.7^[3]

^{https://en.wikipedia.org/wiki/Wireless_USB}

A radio pack is mainly used for musicians such as guitarists and singers for live performances. It is a small radio transmitter that is either placed in the strap or in the pocket. The receiver is connected to an amp or PA system and the user simply connects the transmitter into the instrument. By using a wireless system, musicians are free to move around the stage. This has meant that more elaborate stage shows are now possible, with musicians performing a long way from the amplifier or speakers.

As with any radio device interference is possible, although modern systems are more stable. An example of a performer who has made use of a radio pack is AC/DC guitarist Angus Young, whose stage antics are legendary. 

https://en.wikipedia.org/wiki/Radio_pack

Radio jamming is the deliberate jamming, blocking or interference with wireless communications.^[1] In some cases, jammers work by the transmission of radio signals that disrupt communications by decreasing the signal-to-noise ratio.^[2]

The concept can be used in wireless data networks to disrupt information flow.^[3] It is a common form of censorship in totalitarian countries, in order to prevent foreign radio stations in border areas from reaching the country.^[2]

0:43

Vietnamese siren jammer trying to jam Radio Dap Loi Song Nui, an anti-government and communist radio station.

Jamming is usually distinguished from interference that can occur due to device malfunctions or other accidental circumstances. Devices that simply cause interference are regulated differently. Unintentional "jamming" occurs when an operator transmits on a busy frequency without first checking whether it is in use, or without being able to hear stations using the frequency. Another form of unintentional jamming occurs when equipment accidentally radiates a signal, such as a cable television plant that accidentally emits on an aircraft emergency frequency. 

https://en.wikipedia.org/wiki/Radio_jamming

Radio-in-a-box (RIAB) is a portable, economical broadcasting system containing a laptop, mixer, CD/Cassette player, digital audio recorder, microphones and equipment needed to establish a radio station in remote or disaster locations.^[1] 

https://en.wikipedia.org/wiki/Radio_in_a_box

Radio frequency sweep or frequency sweep or RF sweep apply to scanning a radio frequency band for detecting signals being transmitted there. A radio receiver with an adjustable receiving frequency is used to do this. A display shows the strength of the signals received at each frequency as the receiver's frequency is modified to sweep (scan) the desired frequency band. 

https://en.wikipedia.org/wiki/Radio-frequency_sweep

Overhead radio frequency power transmission line at Solec Kujawski longwave transmitter, Solec Kujawski, Poland

Radio frequency power transmission is the transmission of the output power of a transmitter to an antenna. When the antenna is not situated close to the transmitter, special transmission lines are required.

Bushing

The most common type of transmission line for this purpose is large-diameter coaxial cable. At high-power transmitters, cage lines are used. Cage lines are a kind of overhead line similar in construction to coaxial cables. The interior conductor is held by insulators mounted on a circular device in the middle. On the circular device, there are wires for the other pole of the line.

Conductor bundle with spacer insulator

Cage lines are used at high-power transmitters in Europe, like longwave transmitter Topolna, longwave-transmitter Solec Kujawski and some other high-power transmitters for long-, medium- and shortwave.

For UHF and VHF, Goubau lines are sometimes used. They consist of an insulated single wire mounted on insulators. On a Goubau line, the wave travels as longitudinal currents surrounded by transverse EM fields. For microwaves, waveguides are used. 

https://en.wikipedia.org/wiki/Radio_frequency_power_transmission

A radio access network (RAN)^[1] is part of a mobile telecommunication system. It implements a radio access technology. Conceptually, it resides between a device such as a mobile phone, a computer, or any remotely controlled machine and provides connection with its core network (CN). Depending on the standard, mobile phones and other wireless connected devices are varyingly known as user equipment (UE), terminal equipment, mobile station (MS), etc. RAN functionality is typically provided by a silicon chip residing in both the core network as well as the user equipment. See the following diagram:

     CN
    /  ⧵
   /    ⧵
 RAN    RAN
 / ⧵    / ⧵
UE UE  UE UE

Examples of radio access network types are:

• GRAN: GSM radio access network
• GERAN: essentially the same as GRAN but specifying the inclusion of EDGE packet radio services
• UTRAN: UMTS radio access network
• E-UTRAN: The Long Term Evolution (LTE) high speed and low latency radio access network

It is also possible for a single handset/phone to be simultaneously connected to multiple radio access networks. Handsets capable of this are sometimes called dual-mode handsets. For instance it is common for handsets to support both GSM and UMTS (a.k.a. "3G") radio access technologies. Such devices seamlessly transfer an ongoing call between different radio access networks without the user noticing any disruption in service.

See also

• AirHop Communications
• IP connectivity access network
• C-RAN

References

1. 
   

1. "What is a Radio Access Network (RAN)?". SearchNetworking. Retrieved 2022-02-22.

Category:

• Radio technology

 https://en.wikipedia.org/wiki/Radio_access_network

Frequency Coordination is a technical and regulatory process that removes or mitigates radio-frequency interference between different radio systems that operate on the same frequency.

Normally frequency coordination is a function of an administration, such as a governmental spectrum regulator, as part of a formal regulatory process under the procedures of the Radio Regulations (an intergovernmental treaty text that regulates the radio frequency spectrum).^[1]

Before an administrations lets an operator operate a new radio communications network, it must undergo coordination in the following steps:

• Inform other operators about the plans
• Receive comments if appropriate
• Conduct technical discussions with priority networks
• Agree on technical and operational parameters
• Gain international recognition and protection on the Master International Frequency Register
• Bring the network into use

This coordination ensures that:

• All administrations know the technical plans of other administrations.
• All operators (satellite and terrestrial) can determine if unacceptable interference to existing and planned “priority” networks is likely, and have an opportunity to:
  • Object
  • Discuss and review
  • Reach technical and operational sharing agreements

Coordination is thus closely bound to date of protection or priority, defined by the date when the International Telecommunication Union receives complete coordination data. New planned networks must coordinate with all networks with an earlier date of protection but are protected against all networks with a later date of protection. Planned (but not implemented) networks acquire status under this procedure, but time limits ensure that protection does not last forever if networks are not implemented.

Congress Authorizes FCC

In 1982, the United States Congress provided the FCC with the authority to use frequency coordinators:

• Assist in developing and managing spectrum
• Recommend appropriate frequencies (designated under Part 90).

List of Coordinators

For Public Safety frequency coordination -

• AASHTO^[2]
• APCO^[3]
• FCCA^[4]
• IMSA^[5]

For Business and special emergency -

• AAA^[6]
• AAR^[7]
• EWA^[8]
• FIT^[9]
• PCIA^[10]
• UTC^[11]
• Micronet Communications, Inc. - Since 1983^[12]

References

1. 
   

International Telecommunication Union

https://frequencycoordination.transportation.org/ Frequency Coordinator

http://www.apcointl.org/spectrum-management.html/ Frequency Coordinator

http://www.fcca.info/ Frequency Coordinator

http://www.imsasafety.org/ Frequency Coordinator

http://aaa.radiosoft.com/ Frequency Coordinator

http://www.aar.com/aar_rf.php Frequency Coordinator

http://www.enterprisewireless.com/ Frequency Coordinator

http://www.fcclicense.com/ Frequency Coordinator

http://llink.pcia.com/crdfee.htm Frequency Coordinator

http://utc.org/utc/utc-spectrum-services/ Archived 2010-11-08 at the Wayback Machine Frequency Coordinator

12. https://www.micronetcom.com/ Frequency Coordinator

Category:

• Radio technology

https://en.wikipedia.org/wiki/Frequency_coordination

Dynamic carrier control (DCC) is a method of reducing power consumption in radio transmitters during periods of low audio activity or silence. It is a type of Modulation-Dependent Carrier Level control, or MDCL. All modern high-power (>50 kW) shortwave radio transmitters incorporate DCC of some kind, as well as some mediumwave (MW) transmitters.

DCC causes the carrier wave level to be automatically reduced when the audio is very weak or no audio is present. During periods of silence (no audio), the carrier power is reduced by 50%, so the 250 kW transmitter is putting out a carrier of 125 kW during audio pauses. This carrier power reduction saves electricity. 

https://en.wikipedia.org/wiki/Dynamic_carrier_control

Data Radio Channel (DARC) is a high-rate (16 kbit/s) standard for encoding data in a subcarrier over FM radio broadcasts. It uses a frequency of 76kHz, the fourth harmonic of the FM radio pilot tone.

DARC was approved as the All-European standard ETS 300 751 in 1997.^[1]

^{https://en.wikipedia.org/wiki/Data_Radio_Channel}

An off-air pickup or off-the-air pickup is a method by which the direct signal from a radio or television station is received and then rebroadcast by another station, CATV system,^[1] or satellite television feed. It was often used to distribute network broadcast programming to smaller markets which were normally outside of the range of major centers. 

https://en.wikipedia.org/wiki/Off-air_pickup

C-RAN (Cloud-RAN), also referred to as Centralized-RAN, is an architecture for cellular networks.^[1][2][3] C-RAN is a centralized, cloud computing-based architecture for radio access networks that supports 2G, 3G, 4G and future wireless communication standards. Its name comes from the four 'C's in the main characteristics of C-RAN system, "Clean, Centralized processing, Collaborative radio, and a real-time Cloud Radio Access Network".^[4] 

https://en.wikipedia.org/wiki/C-RAN

Local multipoint distribution service (LMDS) is a broadband wireless access technology originally designed for digital television transmission (DTV). It was conceived as a fixed wireless, point-to-multipoint technology for utilization in the last mile.^[1] LMDS commonly operates on microwave frequencies across the 26 GHz and 29 GHz bands. In the United States, frequencies from 31.0 through 31.3 GHz are also considered LMDS frequencies.^[2]

Throughput capacity and reliable distance of the link depends on common radio link constraints and the modulation method used – either phase-shift keying or amplitude modulation. Distance is typically limited to about 1.5 miles (2.4 km) due to rain fade attenuation constraints. Deployment links of up to 5 miles (8.0 km) from the base station are possible in some circumstances such as in point-to-point systems that can reach slightly farther distances due to increased antenna gain. 

https://en.wikipedia.org/wiki/Local_multipoint_distribution_service

In a radio receiver, a bandspread control is a secondary tuning control that allows accurate tuning of closely spaced frequencies of a radio band.^[1] With a main tuning control that covered a wide range of frequencies, for example 10-14 megahertz in a few turns of the tuning knob, a very small motion might change the tuning by tens of kilohertz and would make accurate tuning to any particular frequency difficult. A calibrated bandspread tuning control allows the main tuning to be set to a predefined spot on the control, and the bandspread allows tuning of a particular frequency within some restricted range of the main tuning control.

One method of adding a bandspread control was to put a relatively small value variable tuning capacitor and dial directly in parallel with the main tuning variable capacitor ( or connected to a tap on the coil of the tuned circuit). The smaller capacitor would have much less effect on the resonant frequency than the main capacitor, allowing fine discrimination of the tuned frequency.^[2] A second method, mechanical bandspread, was a second tuning knob connected through a gear train to the main tuning knob; each turn of the bandspread dial moved the main dial through a small part of its range, improving the precision of tuning.^[3]

Bandspread controls were found on communications receivers, amateur radio receivers, and some broadcast receivers. With the advent of digital frequency synthesizers that could be set with high resolution by a keypad or incremental tuning knob, the requirement for bandspread control in many applications was eliminated.

In the mid-1960s, some British portable radios^[4] had a separate 'Bandspread' waveband covering the highest frequencies of the medium wave (AM) band (typically 1400 – 1600 kHz) to simplify tuning of popular commercial stations such as the offshore Radio Caroline and the continental Radio Luxembourg. A single tuning knob was used for all wavebands. 

https://en.wikipedia.org/wiki/Bandspread

Category:Radio technology

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Contents

• Top
• 0–9
• A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Subcategories

This category has the following 16 subcategories, out of 16 total.

 

• 
  

• Radio electronics‎ (8 C, 166 P)

A

• 
  

• Antennas (radio)‎ (4 C, 176 P)

B

• 
  

• Bluetooth‎ (2 C, 35 P)

C

• 
  

• Cable radio‎ (12 P)

D

• 
  

• Digital radio‎ (5 C, 31 P)

E

• 
  

• Electromagnetic compatibility‎ (2 C, 48 P)

M

• 
  
  
  

Microwave technology‎ (4 C, 101 P)

• Radio modulation modes‎ (3 C, 50 P)

P

• 
  

Radio transmission power‎ (6 P)

• Radio frequency propagation‎ (6 C, 103 P)

R

• 
  

Radio frequency antenna types‎ (2 C, 110 P)

Radio resource management‎ (2 C, 82 P)

• RF connectors‎ (44 P)

S

• 
  

Satellite radio‎ (2 C, 11 P)

• Software-defined radio‎ (3 C, 22 P)

T

• 
  

• Terahertz technology‎ (25 P)

Pages in category "Radio technology"

The following 161 pages are in this category, out of 161 total. This list may not reflect recent changes.

0–9

• 800 MHz frequency band

A

• Air interface
• Airtime (software)
• Alternative frequency
• AM stereo
• AMAX
• Amplitude modulation signalling system
• Antenna tuner
• Antenna tuning hut
• Apex (radio band)
• Armstrong phase modulator
• Attack-time delay
• Autofahrer-Rundfunk-Informationssystem
• Automatic gain control
• Automatic message exchange

B

• Bandspread
• Bandstacked
• BBC Research & Development
• Block upconverter
• Blocking (radio)

C

• C-QUAM
• C-RAN
• Cable grommet
• Campcaster
• Carrier current
• CCIR (selcall)
• Chirp transmitter
• Circulator
• Clerk Maxwell Prize
• Radio clock
• Clyde Broadcast
• Cognitive radio
• Coherent electromagnetic radio tomography
• Comfort noise
• Common Public Radio Interface
• Comparison of radio systems
• Connectivity exchange
• Continuous Tone-Coded Squelch System
• CRM 114 (fictional device)
• Crossband operation

D

• Data Radio Channel
• Datacasting
• Dipole antenna
• Discontinuous reception
• Discontinuous transmission
• Dynamic carrier control
• DYNAS
• DySPAN

E

• EF Johnson Technologies
• Enhanced other networks

F

• Falsing
• Family Radio Service
• Frequency coordination
• Frequency synthesizer

G

• General Mobile Radio Service
• Generalized signal averaging
• GoTenna
• Grid-leak detector

H

• Huawei SingleRAN

I

• Institut für Rundfunktechnik
• Institute of Radio Engineers
• Institution of Electronic and Radio Engineers

K

• Kitzbüheler Horn Transmitter
• Klotz Digital

L

• Link quality analysis
• Local multipoint distribution service
• Low-power broadcasting

M

• Marantz 2600
• Marconi's law
• Medical applications of radio frequency
• Microphonics
• Microwave
• Microwave welding
• Mobile phone
• Motus (wildlife tracking network)
• Multipath mitigation
• Music scheduling system

N

• Nanoradio
• Nautel
• Near-field electromagnetic ranging
• Networked flying platform
• NHK Science & Technology Research Laboratories
• Nizhny Novgorod Radio Laboratory

O

• Off-air pickup
• OpenBroadcaster
• Operation RAFTER

P

• PACTOR
• Personal radio service
• Pioneer SX-1980
• Plate detector (radio)
• PMR446
• Pocket FM
• Program-associated data
• Programme identification
• Project Diana
• PTT ID
• Public Radio Service

R

• Radio access network
• Radio Data System
• Radio frequency power transmission
• Radio-frequency sweep
• Radio in a box
• Radio jamming
• Radio over fiber
• Radio pack
• Radio resource management
• Radio spectrum scope
• Radio teleswitch
• Radio transmitter design
• Radio wave
• Magneto Inductive Remote Activation Munition System
• Personal RF safety monitor
• Radio frequency
• Radio-frequency engineering
• Remote Activation Munition System
• Radio-frequency skin tightening
• Radio-frequency welding
• RadioDNS
• Radiophysics
• Radioplayer
• Computation of radiowave attenuation in the atmosphere
• Receive-after-transmit time delay
• Remote radio head
• RF power margin

S

• Hohe Salve
• Satellite radio
• Schafer automation system
• Selcall
• Selective calling
• Self-interference cancellation
• Shared mesh
• Signal analyzer
• Signal transition
• Sky Gnome
• Software Communications Architecture
• Spatial modulation
• Spectrum analyzer
• Spurious emission
• Spurious tone
• Stubline transmitter
• Subaudible tone
• Switched mesh
• Symmetrical double-sided two-way ranging

T

• Television antenna
• Tikker
• Tonio (app)
• Traffic announcement (radio data systems)
• Traffic message channel
• Transmit-after-receive time delay
• Transmitter station
• TV radio

U

• Ultra-wideband
• Unlicensed Personal Communications Services

V

• Visual radio

W

• Waveguide rotary joint
• Winmor
• Wireless mesh network
• Wireless USB
• Wunderlich (vacuum tube)

Y

• Y-factor

Z

• Zetron

Categories:

• Broadcast engineering
• Telecommunications engineering
• Information and communications technology
• Sound production technology
• Radio

Hidden categories:

• Commons category link from Wikidata
• Template Category TOC via CatAutoTOC on category with 101–200 pages
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 https://en.wikipedia.org/wiki/Category:Radio_technology