The Gamer's Guide to Radiowaves

“Here are your communication devices for Korea. Unlimited range, also equipped with audio surveillance system.”
The quotation from Black Panther is typical of how communications are generally treated. The communicator is shirt-button sized object that is stuck in the ear (or occasionally behind it). If it does not have infinite range it is at least international. You will get perfect reception inside an underground base, submerged submarine or within a steel bank vault!
Another staple, the homing bug can be equally astounding. Some of the GURPS rules are a little more realistic. The tag round (THS 3e p.158) has a transmission range of only a mile. For a 4mm calibre round it seems likely that frequency is unlikely to be longer than high UHF, at best. Metal vehicle bodies and terrain are likely to play havoc with reception of those microwaves. A 15mm tag micromissile may be more capable of using longer wavelengths.
A little realism poses problems for the conspiracy theorist. If implants are only a few millimetres across, how exactly are those implants transmitting to the aliens/government? Interestingly, the tin foil hat may actually block any microwaves! Practical power source aside, radiowaves of this frequency could potentially cook the surrounding tissue if sufficiently energetic to have a useful range.
The radio spectrum will be an important facet of the THS-verse. Many characters will have VIIs or equivalent wearables. Some characters may be the AIs in such devices. It seems likely that much of the communication between these devices and their users and the outside world will be in the microwave range. Just what happens if the terrain is unfavourable and there are no relays? How clever and useful will your AI be when it cannot connect to the information web? Criminals may deliberately create “dead zones” so victims cannot call for assistance. In certain conditions a character may need to carry a device to allow their VII to utilize UHF and VHF wavelengths. Long-range line of sight transmissions such as to satellites may also need additional hardware. A antenna implant for longer wavelength transmissions may be an option. Perhaps this could be combined with a tail biomod!
Communication delay (time-lag or light-lag) may also be significant. Any transmission that passes via a satellite has a delay of a quarter of a second each way. For a two-way communication, such as operating a remote or telepresence, this is a half second pause between a stimulus and a reaction. THS 3e p.144 suggests actions such as dodging and shooting take a -1 penalty per 10,000 miles range. Light-lag in seconds is 500 x distance in AU. Table below taken from here.
Geosat Link (US-Aus) 0.25 sec.
Earth-Moon 1.3 sec.
Earth-Mars 3-21 minutes.
Earth-Jupiter 33-53 minutes.
Earth-Pluto 5 hours. 
Below is a quick crash course in the radio spectrum. To save time I have edited most of this from Wikipedia. Refer to the original articles for further detail on some of the topics mentioned. I have mainly concentrated on communication related uses. Some of these wavelengths have other interesting applications. Hopefully what I have included will give you some ideas for scenarios or other ways that some added realism can make games can make games more interesting.
Frequencies are expressed in hertz (cycles per second). Personally I find it easier to understand how they may interact with the world if converted into wavelength. The formula for this is given below. You will see there is a direct correlation between range, clarity, penetration and bandwidth.

Conversion to metre bands: metres=300,000/frequency in KHz or 300/frequency in MHz.
“I canna’ change the laws of physics. I’ve got to have thirty minutes.. Scott to Kirk, Star Trek Episode: The Naked Time.
ELF (Extremely Low Frequency) 3 to 30 Hz/wavelengths: 100,000 to 10,000 kilometres. Actually classed as a “subradio” frequency. ELF can potentially penetrate hundreds of metres of seawater, so has applications for communication with submarines. Constructing a practical ELF transmitting station poses considerable challenges. The proposed US Project Sanguine would have occupied two-fifths of the state of Wisconsin and required 800 Megawatts of power.
SLF (Super Low Frequency) 30 to 300 Hz/wavelengths: 10,000 km to 1000 km. 30 to 300 Hz is sometimes called “ELF”.
Like ELF, SLF can be used to communicate with deep diving submarines. A SLF transmitting station requires a large area with very low ground conductivity. The Russian ZEVS station (83 Hz/3,656 km wavelength), for example, has 60 km between its electrodes. The US Project ELF (at 76 Hz/wavelength 3,945 km, actually SLF) used two installations 135 km apart. Due to the considerable technical requirements, expense and rarity of suitable locations only a few nations have SLF communication facilities. At SLF frequencies the bandwidth of the transmission is very small, so a system can only send short coded text messages at a very low data rate. Reportedly it took Project ELF 15 minutes.o transmit a single three-letter code group. Submarines cannot transmit back so a ELF-VLF signal is often followed by communication using higher frequency radio.
ULF (Ultra Low Frequency) 30 Hz to 3 KHz/wavelength: 1000 to 100 km. Used for communication in underground mines as it can penetrate the ground. Naturally generated bursts of ULF have been detected before some earthquakes. “Earth-mode” communications used in World War One. May or may not have seen later military use for communications through the ground. Due to the impractical size for a full wave resonant antenna, range is usually limited to just a few kilometres. Receiving a 10-100 W signal at this distance would require electrodes hammered into the ground 10-50 m apart.
VLF (Very Low Frequency) 3 to 30 KHz/wavelengths: 100 to 10 km. The band is also known as the “myriametre band/wave” as the wavelengths range from one to ten “myriametres” (myriametres; an obsolete, non-SI, metric unit equal to 10 kilometres). Due to its limited bandwidth, audio (voice) transmission is highly impractical in this band, and therefore only slow, low data rate coded signals are used, of the order of a few characters each minute. The VLF band is used for a few radio navigation services, government time radio stations (broadcasting time signals to set radio clocks) and communication to submarines. VLF waves can penetrate at least 40 metres (120 ft) into saltwater, so are used for secure military communication, particularly with submarines. VLF radio waves can diffract around large obstacles and so are not blocked by mountain ranges or the horizon, and can propagate as ground waves following the curvature of the Earth, or follow the waveguide between the Earth’s surface and ionosphere. VLF transmissions are very stable and reliable, and are used for long distance communication. Propagation distances of 5,000 to 20,000 km have been realized.
Constructing a full wave resonant antenna for a VLF system is impractical, so transmitting antennas are a small fraction of a wavelength long. Even so, transmitting antennas may be over a mile across and use very high power (~1 megawatt) sources. Receiving antennas can be considerably smaller since great efficiency is not needed. Submarines usually use a long antenna raised by a buoy.
LF (Low Frequency) 30 to 300 KHz/wavelengths: 10 to 1 km. Known as the “kilometre band/wave”.
LF Uses: aircraft beacons, navigation (LORAN), information, and weather systems. Some time signal broadcasts (“radio clocks”). AM “Longwave/LW” broadcasting. Some radio frequency identification (RFID) tags utilize very short range LF.
LF Propagation: Long wavelength, low frequency radio waves can diffract over obstacles like mountain ranges and travel beyond the horizon, following the contour of the Earth. This mode of propagation, called ground wave, is the main mode in the LF band. Low frequency ground waves can be received up to 2,000 kilometres (1,200 miles) from the transmitting antenna. Skywave or “skip” propagation can occur, but is less common than with higher frequencies/shorter wavelengths. Skywave LF signals can be detected at distances exceeding 300 kilometres (190 miles) from the transmitting antenna.
LF Antenna: Due to its use of ground waves LF is most effectively transmitted by vertical antennas. The long wavelength means most antennas are of less than quarter wavelength. Navigational beacons and LW broadcasting stations may use masts approaching 200 metres in height
Signals below 50 KHz are capable of penetrating depths of saltwater. The US Ground Wave Emergency Network (GWEN) at 150-175 KHz was a land-based system formerly used to communicate with submarines, being capable of continued operation after a nuclear attack.
MF (Medium Frequency) 300 KHz to 3MHz (3000 KHz)/wavelength: 1000 to 100 metres. Known as “hectometre band” as the wavelengths range from ten to one “hectometre”
MF Uses: Medium wave (MW) AM broadcast band. Also used for navigational radio beacons, maritime ship-to-shore communication, and transoceanic air traffic control. Many home-portable or cordless telephones, especially those that were designed in the 1980s, transmit low power FM audio signals between the table-top base unit and the handset on frequencies in the range 1600-1800 KHz/1.6-1.8 MHz.
MF Propagation: Radio waves at MF/MW wavelengths propagate via ground waves and reflection from the ionosphere (skywaves). Ground waves follow the contour of the Earth. At these wavelengths they can bend (diffract) over hills, and travel beyond the visual horizon, although they may be blocked by mountain ranges. Typical MF radio stations can cover a radius of several hundred miles from the transmitter, with longer distances over water and damp earth. MF waves can also travel longer distances via skywave propagation, but this is variable with time of day, season and solar activity. When the ionosphere is heavily ionised, such as during the day, in summer and or at times of high solar activity, MF waves can be absorbed. At night, in winter or during low solar activity, MF signals can be refracted and received hundreds or thousands of miles away. This may cause interference with other MW stations.
MF Antenna: Primarily using ground wave propagation, MW stations use vertical antenna, typically “quarter wave” of 25-250 metres. Receiving antennas are small enough that they are usually enclosed within the case of an AM receiver. Reception is at its best when the rod is at right angles to the transmitter. Ferrite antennas are often used for AM radios and these are also used in portable radio direction finders.
Early in the First World War, aircraft radio systems for Morse and voice transmission typically used MF 100–260 m (1.15–3 MHz). Artillery spotter aircraft lowered a trailing aerial wire of around 100-200 ft (30.5–61 m) in length, with a lead weight at the end. A portable system intended for ground troops requited three men, one holding the end of an antenna 50 ft ahead of the operator, the other 50 ft behind. Not surprisingly, many infantry stuck with their carrier pigeons and messenger dogs!
HF (High Frequency) 3 MHz to 30 MHz/wavelength: 100 to 10 metres. Also known as the “decametre band/wave” as its wavelengths range from one to ten “decametres”.
HF Uses: The band is used by international and regional shortwave broadcasting stations (2.31–25.82 MHz) eg BBC World Service and Voice of America, aviation and air-to-ground communication, maritime sea-to-shore and ship-to-ship services, over-the-horizon radar systems, Global Maritime Distress and Safety System (GMDSS) communication, government time stations, military and governmental communication systems, clandestine and numbers stations, weather stations, amateur radio and citizens band services, studio-to-transmitter (STL) radio links, radio control devices for models and radio paging transmitters, among other uses. Some radio frequency identification (RFID) tags utilize HF.
HF Propagation: The dominant means of long-distance communication in HF band is skywave (“skip”) propagation. HF radio waves can travel beyond the horizon, around the curve of the Earth, and can be received at intercontinental distances. The refractive tendency of the ionosphere is influenced by a number of factors, including time of day, season, solar activity, sunspots, and polar aurora. HF works well on summer days while MF may be better on winter nights. At optimal conditions a HF transmitter may have global reach for relatively little power. Limited groundwave propagation means that under certain conditions a HF frequency may be useless. “Broadband over power lines” (BPL) Internet access adversely affects HF communications, as do some electronic devices such as plasma televisions.
HF Antenna: Transmission of skywaves favours horizontally orientated antennae. Use of efficient “quarter wave” to “full wave” antennae becomes practical, although these may be in excess of ten metres long. Use of long range HF radios is therefore restricted to static positions or large vehicles such as airliners or naval vessels.
Spies and reconnaissance troops have used HF transmitters, but needed to find a suitable location in which to erect their antenna and remain safe while halted for use. Given that communication satellites will be a prime target for enemies in future conflicts, the capability to transmit at HF wavelengths is likely to remain important.
The British No.18 Manpack radio of the Second World War used 6 to 9 MHz with an RF output of 0.25 W. Range was up to 10 miles. The US SCR-536 “Handy-Talkie” hand-held used a 3.5 and 6.0 MHz frequency range but had a range of a mile or less due to the short antenna. OSS and SOE issued radios that worked in the 2 to 17 MHz ranges with a claimed range of 200-1000 miles. Most were suitcase-sized, but one model, the SSR-5, was under 3 lbs!
There is a Modesty Blaise story where it is claimed she detects a distress signal from halfway around the world on the “shortwave” in her car. This is highly unlikely, since the vehicle would be too small to mount an antenna likely to have such a performance. Technically, a CB radio is a “shortwave”, but these were illegal and not available in the UK when the story was set.
Shortwave (SW)” is a term that includes the HF wavelengths but may also include MF frequencies down to 2 MHz. Some dictionaries define it as “frequencies of over 1600 KHz/1.6 MHz”. SW is somewhat less prone to interference from thunderstorms than medium wave radio, making it useful in tropical regions or for broadcasts during extreme weather emergencies.
CB (“Citizen’s Band”) radio is technically SW/HF, usually being 40 (in some countries, 80) allocated channels around the 11 metre/27 MHz range. Upper bands of HF (26.5-30 MHz) share some characteristics with low VHF. A “quarter-wave” antenna for CB frequencies must be 2.7 metres/9 ft or its equivalent. This may have contributed to its initial popularity on larger vehicles such as trucks. Although perceived as a relatively short-ranged means of communication, as a HF system CB transmissions can propagate by skywave and depending on the ionosphere, sometimes transmission of thousands of kilometres have been made.
VHF (Very High Frequency) is 30 to 300 MHz/wavelength: 10 to 1 metre.
VHF Uses: Radio waves in the VHF band are used for digital audio broadcasting (DAB) and FM radio broadcasting, television broadcasting, two-way land mobile radio systems (emergency, business, private use and military), long range data communication (up to several tens of kilometres with radio modems), amateur radio (6 metre band and others), and marine communications. Air traffic control communications and air navigation systems. Radio controlled toys and model aircraft, industrial remote control, cordless telephones, baby monitors, wireless microphones, TV/FM remote broadcast pickup. Early animal radio-tracking devices used VHF.
VHF Propagation: Radio waves in the VHF band propagate mainly by line-of-sight and ground-bounce paths. They do not follow the contour of the Earth as ground waves and so are blocked by hills and mountains, although because they are weakly refracted by the atmosphere they can travel somewhat beyond the visual horizon out to about 160 km (100 miles). VHF waves therefore have a “radio horizon” that is further than the visual horizon. Occasionally, when conditions are right, VHF waves can travel long distances by “tropospheric ducting” due to refraction by temperature gradients in the atmosphere. VHF can penetrate building walls and be received indoors, although in urban areas reflections from buildings cause multipath propagation.
VHF Antenna: The VHF band is the first band at which efficient transmitting antennas are small enough that they can be mounted on vehicles and man- portable devices, so the band is used for two-way land mobile radio systems, such as walkie-talkies, and two way radio communication with aircraft (Airband) and ships (marine radio). A quarter-wave whip antenna would be 25 cm to 2.5 metre.
Ground Penetrating Radar: GPR uses high-frequency EM signals in the microwave range, typically between 10 megahertz (MHz) and 2.6 gigahertz (GHz).


“Micro” in this context means small, rather than indicating a wavelength in the micrometre range (which would be infrared light, rather than a radiowave). Microwaves are defined as 300 MHz (1 metre) to 300 GHz (1 mm), which includes UHF, SHF and EHF (millimetre wave). An alternative definition is 1 to 100 GHz (wavelengths between 0.3 metre and 3 mm), which covers the SHF band but only part of the UHF and EHF. Microwaves of either definition travel by line-of-sight and do not diffract around hills, nor follow the earth’s surface as ground waves, nor reflect from the ionosphere. Terrestrial microwave communication links are limited by the visual horizon to about 40 miles (64 km). Microwave-band systems are widely used in modern technology, in point-to-point communication links, wireless networks, microwave radio relay networks, radar, ground-penetrating radar, and satellite and spacecraft communication.
UHF (Ultra High Frequency) radio frequencies have the range 300 MHz to 3 GHz (3000 MHz)/wavelength: 1 metre to 0.1 metre (10 cm), also known as the decimetre band as the wavelengths range from one metre to one tenth of a metre (one decimetre).
UHF Uses: UHF is used for television broadcasting, mobile (cell) phones, satellite communication including GPS, personal radio services including Wi-Fi and Bluetooth, walkie-talkies, cordless phones, garage door openers, automobile keyless entry systems, radio microphones, pagers, alarm monitoring, RFID, radar systems, amateur radio (ham: 70, 23, 33, 13 cm bands), digital audio broadcasting, commercial aviation air-ground systems and numerous other applications.
UHF Propagation: UHF radio waves propagate mainly by line of sight and ground reflection. UHF is blocked by hills and large buildings and cannot travel beyond the horizon, although the transmission through building walls is strong enough for indoor reception. UHF has a shorter wavelength than VHF, which makes it easier for the signal to find its way through smaller wall openings to the inside of a building. When used within a building its shorter wavelength travels through small openings inside the building better than VHF or longer wavelengths. Since the wavelengths of UHF waves are comparable to the size of buildings, trees, vehicles and other common objects, reflection and diffraction from these objects can cause fading due to multipath propagation, especially in built-up urban areas. Since UHF transmission is limited by the visual horizon to 30–40 miles (48–64 km) and usually to shorter distances by local terrain, it allows the same frequency channels to be reused by other users in neighbouring geographic areas (frequency reuse). Radio repeaters are used to retransmit UHF signals when a distance greater than the line of sight is required. Occasionally UHF radio waves can travel long distances by tropospheric ducting.
UHF Antenna: At UHF frequencies a quarter-wave monopole, the most common omnidirectional antenna, is between 2.5 and 25 cm long. Many hand-held and other small devices use UHF wavelengths.
SHF (Super High Frequency) are radio frequencies in the range 3 to 30 GHz/wavelength: 10 to 1 cm. This band of frequencies is also known as the “centimetre band/wave”
SHF Uses: SHF frequency range is used for most radar transmitters, wireless LANs, satellite communication, microwave radio relay links, many short range terrestrial data links and microwave cooking.
SHF Propagation: Centimetre waves propagate solely by line of sight. Penetration through building walls enough for useful reception may be problematic if there are obstructions such as furniture or people. The wavelength of SHF waves creates strong reflections from metal objects the size of automobiles, aircraft, ships, and other vehicles. This is useful for radar, but not for SHF communication systems. Attenuation and scattering by moisture in the atmosphere increases with frequency, limiting the use of high SHF frequencies for long-range applications.
SHF Antenna: Wavelengths are small enough at centimetre wave frequencies that the antenna can be much larger than a wavelength, allowing highly directional (high gain) antennas to be built which can produce narrow beams. Therefore, they are used in point-to-point terrestrial communications links, limited by the visual horizon to 30–40 miles (48–64 km). By using troposcatter, specialized communications systems operating at a few GHz, may communicate beyond the horizon.
The wavelengths of SHF waves are small enough that they can be focused into narrow beams by high gain directive antennas from a half metre to five metres in diameter.
SHF is the lowest frequency band where radio waves can be directed in narrow beams by conveniently-sized antennas so they do not interfere with nearby transmitters on the same frequency, allowing frequency reuse. On the other hand, they are the highest frequencies which can be used for long distance terrestrial communication; higher frequencies in the EHF (millimetre wave) band are highly absorbed by the atmosphere, limiting practical propagation distances to one kilometre. The high frequency gives microwave communication links a very large information-carrying capacity (bandwidth).
EHF (Extremely High Frequency) is 30 to 300 GHz/wavelength: 10 mm to 1 mm. Radio waves in this band are called the millimetric or millimetre band/waves, sometimes abbreviated to mmW or mmWave.
EHF Uses: Millimetre waves are used for military fire-control radar, Traffic police speed radar, short-range wireless networks, intersatellite links, point-to-multipoint communications and point-to-point high-bandwidth communication links. Since the waves penetrate clothing and their small wavelength allows them to reflect from small metal objects they are used in millimetre wave scanners for airport security scanning. They are used for relatively short range, high resolution radar systems such as weapon guidance. The Microwave Active Denial System (MADS, THS 3e p.156, Changing Times 4e, p.63) emits a beam of millimetre radio waves with a wavelength of 3 mm (frequency of 95 GHz).
EHF Propagation: Millimetre waves propagate solely by line-of-sight paths. At typical power densities they are blocked by building walls and suffer significant attenuation passing through foliage. Radio waves in EHF band have high atmospheric attenuation: they are absorbed by the gases and water in the atmosphere. Therefore, they have a short range and can only be used for terrestrial communication over about a kilometre. Absorption increases with frequency until at the top end of the band the waves are attenuated to zero within a few metres. Absorption by humidity in the atmosphere is significant except in desert environments. In addition, millimetre wavelengths are the same order of size as raindrops so attenuation by rain (rain fade) is a serious problem even over short distances. However the short propagation range allows smaller frequency reuse distances than lower frequencies. Thus, they are useful for densely packed communications networks such as personal area networks.
EHF Antenna: The short wavelength allows modest size antennas to have a small beam width, further increasing frequency reuse potential by use of highly directional, “pencil-beam” transmissions.
THF (Tremendously High/Terahertz Frequency), also known as terahertz waves, terahertz radiation, T-rays, T-waves, T-light, T-lux, THz or submillimetre radiation, consists of electromagnetic waves from 0.3 to 3 THz (300-3000 GHz)/wavelength: 1 mm to 0.1 mm , although the upper boundary is somewhat arbitrary and is considered by some sources as 30 THz/10 micrometres. This is where radiowaves meet infrared. Given millimetre waves can be used for security scanners, it is not surprising that submillimetre waves have similar applications. Terahertz radiation can penetrate fabrics and plastics, so it can be used to uncover concealed weapons on a person, remotely.
In May 2012, a team of researchers from the Tokyo Institute of Technology published in Electronics Letters that it had set a new record for wireless data transmission by using T-rays and proposed they be used as bandwidth for data transmission in the future. The group achieved a signal at 542 GHz (0.553 micrometres), resulting in a data transfer rate of 3 Gigabits per second. The study suggested that Wi-Fi using the system would be limited to approximately 10 metres (11 yd), but could allow data transmission at up to 100 Gbit/s. In 2011, Japanese electronic parts maker Rohm and a research team at Osaka University produced a chip capable of transmitting 1.5 Gbit/s using terahertz radiation. It is highly likely a number of Transhuman Space scenarios could be built around terahertz technologies.
THS Cities of the Edge (4e) tells us that THS communities make extensive use of fibre-optic hard-lines. Radio is mainly used to connect wire terminal-transceivers with mobile systems. It also notes: Indoors, infrared light signals are also used for some communications. They tend to be fairly short range (around 30 feet). Another short-range, low-bandwidth method that is very rare (and hence harder to detect unless one knows what to look for) is ultrasound.
Lasers can pack plenty of information into a signal but have limited range in air; they are more often used in space or for certain indoor environments like robofactories. Near-Ultraviolet Lasers, NULs, have become increasingly common in truly band-width-hungry indoor applications where sunlight cannot reach and humans seldom go – NUL usually indicates that this is an environment solely intended for cybershells.