radio basics

see also:

• Victorian radio
• Radio Signal database and their waterfall appearances - SigIDWiki.com
• CB 2-way radio
• Ham amateur radio
• radio receivers
• software defined radio (SDR) receivers
• transceivers - software defined radio (SDR)
• remote communication for campers and hikers
• radio for campers
• hand crank torch radios for disasters and hiking
• bushwalking in Australia
• navigation management for hikers
• getting a weather forecast when camping or off-grid
• radar and radar motion detector sensors for campers
• radio antennas
• radio RF filters
• satellites and their radio signals
• radio signal intelligence (SigInt)
• electromagnetic interference (EMI)
• oscilloscopes
• vector network analyzers (VNAs)
• signal generators

• there are a variety of radio devices available depending upon needs:
  • receive-only type devices:
    • portable battery operated radios
    • software defined radio (SDR) receivers using laptop and a USB radio dongle with special software and an antenna
  • receive and transmit (transceiver) radios
    • UHF CB radios (no license needed)
    • higher power rated transceivers which need Ham radio licenses to use
    • transceivers - software defined radio (SDR) - generally low power experimental “lab” devices but possession or use of transmit functions may be illegal in Australia
  • field strength or spectrum analyzers
    • debug wifi or other conflicts
    • spectrum analyzers
    • vector network analyzers (VNAs) to assess optimum antenna transmission
    • radio transmission sniffers to detect MAC addresses of radio transmissions, etc
  • approved consumer, industrial or medical devices with approved transmit functions
    • WiFi +/- GPS enabled devices (all are radio waves)
      • computers, smartphones, tablets, printers, WiFi routers, Wifi-enabled TV, home security, “smart home devices”
    • Bluetooth devices
    • satellite communicators
    • standard license-free Industrial, Scientific, Medical (ISM) bands (usually use either 315Mhz, 433MHz or 915MHz ISM bands) used for:
      • radio remote control transmitters for cars, roller doors, photographic flash triggers, etc
      • medical devices such as pacemakers, implantable defibrillators
      • portable telephones

• amplitude modulation (AM)
  • the amplitude (strength) of the radio carrier wave is varied by the modulation signal
  • SSB radio
    • mainly used by Ham radio operators
    • essentially amplitude modulation with one sideband removed
    • only one sideband (either the upper sideband or the lower sideband) is transmitted while the other sideband and the carrier are suppressed
    • this reduces the bandwidth and power requirements compared to conventional AM
    • generated by creating a double-sideband suppressed carrier (DSB-SC) signal and then filtering out one of the sidebands, or equivalently by applying the Hilbert transform to the message signal to produce a complex envelope that cancels one sideband
• frequency modulation (FM)
  • the frequency of the radio carrier wave is varied by the modulation signal
• frequency shift keying (FSK)
  • used in wireless digital devices to transmit digital signals
  • the frequency of the carrier wave is shifted periodically between two frequencies that represent the two binary digits, 0 and 1, to transmit a sequence of bits.
  • FT4 and FT8
    • a digital communication mode used primarily by amateur (ham) radio operators, designed for robust, weak-signal communication over HF and other bands.
    • stands for “Franke-Taylor design, 4-FSK and 8-FSK modulation”, named after its creators Joe Taylor (K1JT) and Steve Franke (K9AN), and was released in 2017 as part of the WSJT software package
    • FT8 uses 8-frequency shift keying (8-FSK) modulation with very narrow bandwidth—approximately 50 Hz
      • communication is done in rapid, automated 15-second transmit/receive cycles, with about 12.6 seconds transmitting and 2.4 seconds decoding
      • can decode signals with an extremely low signal-to-noise ratio (as low as −20 dB to −21 dB in 2500 Hz), enabling reliable contacts under poor propagation conditions, low power (QRP), or weak antennas
      • transmits a very limited but essential set of information to complete a contact: callsigns, signal reports, and acknowledgments—meaning it is not designed for full conversations but for concise, automated contacts
    • has become one of the most commonly used digital modes for weak-signal communication among ham radio operators
  • MSK144
    • designed for meteor scatter detection on VHF bands
  • JT4, JT9, and JT65
    • digital communication modes used in amateur radio, designed for making reliable contacts (QSOs) under weak-signal conditions, especially in challenging propagation environments like Earth-Moon-Earth (EME or moonbounce) and low-power HF operation
  • 4-GFSK (Four-tone Gaussian Frequency-Shift Keying)
    • FST4 and FST4W
      • FST4 supports multiple transmit/receive sequence lengths (from 15 seconds up to 1800 seconds), allowing it to be used in very weak signal conditions, particularly on the low frequency (LF, 30-300 kHz) and medium frequency (MF, 300-3000 kHz) bands
      • FST4W is similar but designed primarily for quasi-beacon transmissions like those used in WSPR, and it uses longer sequence lengths (120 seconds and above)
• phase shift keying (PSK)
  • PSK31
    • a bandwidth roughly 31 Hz, optimized for efficient text transmission and low power use, but without automatic error correction leading to less robustness under bad conditions
    • a digital method used for real-time keyboard-to-keyboard chats with full text typing allowing longer chats and interchange of text
• orthogonal frequency division multiplexing (OFDM) radio systems
  • a family of complicated digital modulation methods very widely used in high bandwidth systems such as WiFi networks, cellphones, digital television broadcasting, and digital audio broadcasting (DAB) to transmit digital data using a minimum of radio spectrum bandwidth.
  • has higher spectral efficiency and more resistance to fading than AM or FM.
• Carrier wave (CW-U)
  • mainly for Morse Code
• sending images as audio signals to create faxes
  • facsimile involves scanning the image and encoding that information.
  • that encoding is transmitted in the form of audio tones which are within the usual voice frequencies and hence can be readily transmitted with either Frequency Modulation (FM) in VHF or UHF bands or Single Sideband for HF bands
  • a computer connected to the receiver's audio out with appropriate software can then decode the audio into a visual image file - usually a GIF.
  • this is often used for weather maps
• other acronyms used
  • QSO
    • in amateur (ham) radio is the term for a two-way radio contact or communication session between two stations
  • IQ signals
    • also known as In-phase (I) and Quadrature (Q) signals, refer to a pair of sinusoidal waveforms of the same frequency that are 90 degrees out of phase with each other. The I signal represents the “in-phase” component, usually a cosine wave, while the Q signal represents the “quadrature” component, shifted by 90 degrees (a sine wave). This orthogonal pair of signals forms the basis for representing, modulating, and demodulating complex radio frequency (RF) signals in communications.
    • allow encoding information into both amplitude and phase of the carrier wave by combining these two components. This is fundamental in modern RF communication systems such as software-defined radios (SDRs), digital down converters, and advanced modulation schemes (e.g., QAM, PSK).
    • the I/Q representation can also be treated mathematically as complex numbers (I as the real part and Q as the imaginary part), enabling detailed signal analysis and processing
    • an IQ signal analyzer will output an I-path trace and a Q-path trace to represent both parts and the raw data can be exported for vector analysis, etc.

• radio waves are similar to light - they are part of the electromagnetic radiation but just different frequencies to light
• the wavelength = speed of light / frequency of the wave
• intensity of the radio wave obeys the same inverse square law that photographers deal with for lights ie. intensity is proportional to 1/(square of the distance)
  • if. every time you double the distance, the intensity drops to a quarter
• they are absorbed by water / humidity / rain which will result in much lower intensity
• they don't pass through metal well - hence your home WiFi may not get through your kitchen or bathrooms well and your CB radio may not communicate behind you if towing a caravan
• most radio waves are line of sight
  • as with visible light, these waves are generally polarised and can be reflected, refracted and diffracted
  • the longer waves can bounce off the ionosphere and travel long distances around earth
• antennas
  • see radio antennas
• the size of the antenna dipole to transmit or receive radio is dependent upon its wavelength hence ultra high frequency 2.4GHz WiFi signals only need a tiny antenna which easily fits inside a mobile phone
• receiver antennas:
  • when the antenna is tuned to a frequency that frequency creates a resonance which then generates an electrical current which is then processed by the radio
  • the ability of a radio to pick up a signal is also dependent on its “gain or sensitivity” which is often measured in dB and means it can pick up signals even if it doesn't exactly match the transmitter however other sources of radio waves can cause interference and noise especially if they are near field
  • the direction of the antenna is important as the waves have a electrical component which is perpendicular to the magnetic component and the receiving antenna needs to be in the same direction as the transmitting antenna for best reception hence most should be vertical (although in practice the waves do bounce around near field objects a bit)
  • FM radio
    • the effectiveness of a whip or telescopic FM antenna is linked to how closely its length matches a quarter of the wavelength for FM radio signals, which occupy 88–108 MHz.
    • a quarter-wave antenna for these frequencies should thus be roughly 69–85 cm (27–33 inches) long, with a center frequency (around 98 MHz) corresponding to about 76 cm (30 inches)
    • most portable FM radios with small telescopic antennae only extend to about 19“ making it more like a 1/6th wave antenna for FM and may match UHF and VHF radio better, but being shorter they may also have a lower gain with broader focus area which may work better in built up areas or hilly regions where direct line of sight is not possible, but tend to be less sensitive for weaker signals
    • the antenna in general should be vertical to match the transmission orientation
    • if using SW, consider a 3m long wire antenna outdoors
• transmitting antennas
  • antennas actually have a small range of frequencies they are resonant for when transmitting
  • these can arc and cause burns if you touch them
  • if you use the wrong antenna for the wavelength you wish to transmit on or no antenna at all, you can get severe reflections back into the radio and overheat and destroy your radio!
  • if only experimenting with transmitting in your “lab” then use a dummy load antenna which has a 50 ohm resistor with a cooling element, will not destroy your radio and will not send strong signals out that would interfere or be illegal ²⁾
    • remember it is only legal to transmit on certain frequency ranges and there can be massive fines or imprisonment

• plaster:
  • plaster alone causes modest attenuation, but plaster with embedded iron mesh (as often used in reinforced plastering) causes significant RF signal attenuation, especially at lower frequencies around 700-900 MHz. The iron mesh acts as a partial shield, increasing attenuation notably in these bands.
• brick walls:
  • brick walls produce moderate attenuation.
  • 11 cm hollow brick range from about 1 dB to 22 dB attenuation over 680 MHz to 2.7 GHz.
  • solid block bricks tend to attenuate about 4-5 dB in this frequency range.
  • attenuation increases with frequency and brick density.
• glass windows:
  • glass transmits radio waves quite well compared to other building materials.
  • it is largely transparent to visible and some infrared wavelengths and generally allows radio waves to pass with minimal attenuation.
  • however, glasses treated with energy-efficiency coatings or metallic films significantly reduce radio wave permeability.
• PVC and polycarbonate:
  • both are mostly transparent to radio waves, better than glass, with very low attenuation at common communication frequencies such as 2.4 GHz.
  • for example, PVC enclosures for antennas cause negligible signal degradation
• aluminium:
  • aluminum causes strong attenuation due to its high conductivity and reflective properties.
  • the attenuation increases with aluminum thickness, but above about 1.3 mm thickness, the increment slows.
  • aluminum effectively blocks radio waves in most practical frequency bands
• steel:
  • steel, similar to aluminum, provides strong attenuation due to conductivity and magnetic properties.
  • attenuation can vary with steel texture and frequency, but it generally acts as an effective barrier against radio waves
• rain:
  • relationship between specific attenuation κ_e (dB/km) and rain rate R (in mm/hr) is often modeled by a power law: κ_e = aR^b, where a and b depend on frequency and polarization. For 19.5 GHz, a≈0.07 and b≈1.1 have been found experimentally.
  • heavy rain around 50 mm/hr can cause specific attenuation depending upon radio wave frequency:
    • MW radio is barely effected by rain as the wavelengths are larger than raindrops and there is minimal absorption or scattering by rain so the specific attenuation is close to zero.
    • VHF FM radio specific attenuation is very low and typically under 0.1 dB/km
    • 2.4GHz WiFi specific attenuation is slightly higher at roughly 0.1 to 0.5 dB/km
    • at 12 GHz it is 20 dB/km, and even more at higher frequencies like 30 GHz, hence microwave data links and radar will generally drop out in heavy rain and presumably Starlink internet will too.

• the radio spectrum from 30Hz to 300GHz is divided into 12 bands including

• electromagnetic fields (EMFs) in the range of 3–30Hz
• common sources include:
  • power lines, substations, power plants, electrical appliances
  • natural: atmospheric lightning activity and disturbances in the planet’s magnetic field, Earth's natural resonances, like the Schumann resonance

• 30-300Hz = 10km - 1000m
• sources:
  • electric power lines and substations
  • large electrical machinery and heavy industrial equipment
  • household and workplace appliances esp. if motors or transformers are involved
  • submarine communications, as these frequencies penetrate seawater more effectively than higher frequencies
  • lightning and ionospheric currents
  • Earth's natural resonances, like the Schumann resonance

• 300–3,000Hz (3kHz) = 1000km - 100km
• sources:
  • some communication systems, particularly those utilizing submarine cables and deep earth exploration
  • large infrastructure installations such as railways and heavy electrical equipment
  • thunderstorms and lightning strikes
  • Earth's magnetosphere - geomagnetic pulsations, solar wind interactions, and magnetic storms
  • seismic and volcanic activity

• 100-519kHz = 3000m - 580m;
• transmitters require a tall radio mast and carrier frequencies are exact multiples of 9 kHz;
• used for broadcasting only within ITU Region 1 including Europe, Russia, Nth Africa
• long-wave signals can travel very long distances up to 1000s of kms
• receivers general use ferrite rods
• 125kHz and 134kHz - low frequency RFID

• 300 – 3000 kHz with wavelength of 1000–100m
• transmitters require a tall radio mast and the whole mast acts as the antenna (whereas FM transmitters generally just have a small antenna on top of the mast)
• in this band the signal to noise ratio is determined by atmospheric noise not receiver antenna size and thus radio receivers can use small ferrite rods for this band
• mostly used for AM radio broadcasting (usually 526.5 kHz to 1606.5 kHz), navigational radio beacons, maritime ship-to-shore communication, and transoceanic air traffic control.
  • in Victoria, ABC Radio Melbourne's AM transmitter at 774 kHz, which broadcasts at 50,000 watts (50 kW) which allows it to be received over most of Victoria
  • see Victorian radio

• 3 – 30 MHz with wavelength of 100–10 m
• most transmitters use AM mode and all use UTC time
• best listening is usually at night pending path of the radio waves
• Single Side Band (SSB) is used by hams and many utility stations and for Morse Code (CW)
  • set radio to SSB, LSB (lower), USB (upper) or BFO (beat frequency oscillator) to access these
• radio waves in this band can be reflected back to Earth by the ionosphere layer in the atmosphere:
  • ionosphere consists of 4 layers:
    • outer F1 (100-300km) and F2 (300-500km) layers generally combine at night time when 40m and 80m radio tends to skip well
    • most of the inner E (100-120km) and D (75-90km) layers generally disappear at night time which allows signals to bounce off the F layer(s)
      • in summer, the E layer gets stronger in daylight hours due to UV light causing increased ionisation which can blanket while the more intense D layer absorbs the radio waves (esp. below 10MHz / above 30m) from reaching the F layer and this effect lasts longer into the evening especially at mid-high latitudes
  • a method known as “skip” or “skywave” propagation
  • these frequencies are suitable for long-distance communication across intercontinental distances and for mountainous terrains which prevent line-of-sight communications
  • noise levels from thunderstorms often reduce usability
  • when all factors are at their optimum, worldwide communication is possible on HF.
• most common antennas in this band are wire antennas such as wire dipoles and the rhombic antenna, and for receiving, random wire antennas are often used.
• used by:
  • international shortwave broadcasting stations (3.95–25.82 MHz) - see http://www.swling.com, http://www.ShortwaveSchedule.com
    • 120m tropical band 2.3-2.495MHz
    • 90m tropical band 3.2-3.4MHz
    • 75m tropical band 3.9-4.0MHz shared with Nth American amateur HAM radio 80m band
    • 60m tropical band 4.75-5.06MHz
    • 49m main band 5.9-6.2MHz
    • 41m 7.2-7.6MHz shared with amateur HAM radio 41m band
    • 31m most heavily used band 9.4-9.9MHz
    • shorter bands down to 11m (25.6-26.1MHz which may be very occasionally used for local digital radio Mondiale DRM broadcasting)
  • aviation communication
  • government time stations
  • weather stations
    • see above for Australia weather faxes - in 2-21MHz range
  • Global Maritime Distress and Safety System (GMDSS) communication
  • some radio frequency identification (RFID) tags utilize HF eg. smartcards, NFC
  • amateur HAM radio
    • in Australia, ham radio frequency bands are: 3.5, 7, 14, 21, 28, 52, 144, 430, 1240, 2400 and 5650 MHz
  • HF citizens band services (generally 27 MHz AM/SSB) in Australia:
    • channel 8: 27.055MHz highway channel
    • channel 9: 27.065MHz emergency channel
    • channel 11: 27.085MHz AM call channel
    • channel 16: 27.155MHz LSB call local
    • channel 35: 27.355MHz LSB call DX
    • maximum is 4 watts for AM and 12 watts PEP for SSB
  • JORN over-the-horizon radar (bounced off the ionosphere) uses 5-30mHz - see radar and radar motion detector sensors for campers
• see also: https://en.wikipedia.org/wiki/Shortwave_radio

• in general, SW reception is best in periods when solar activity cycle is at its peak due to a longer term strengthening of the F layer in the ionosphere which the SW bounces off EXCEPT when there is an actual solar storm hitting earth.
• solar storm activity increases the density of the ionosphere and whilst this will improve reflectivity from the F layer, but it also increases the density of the D layer through which the shortwaves must pass TWICE hence a solar storm hitting earth will generally cause a short-wave fadeout (SWF) or sudden ionospheric disturbance (SID) especially at lower frequencies (especially 5MHz which may be totally blocked, while a moderate effect may be on the 10MHz region where most international broadcasts occur).
• These Fadeouts mostly have a rapid onset of a few minutes as solar storm hits and a slower recovery lasting perhaps an hour although this is highly variable. The high frequencies (eg. 20MHz) are the last to be affected and the first to recover.
• NOTE: the HF circuit is affected ONLY if there is an ionospheric reflection point for the signal in the sunlit hemisphere - it will not occur if that reflection point is in the dark. ³⁾
  • one can check for current SWFs here: https://www.sws.bom.gov.au/HF_Systems/6/2/1

• 30 – 300 MHz with wavelength of 10–1 m
• VHF is the first band at which wavelengths are small enough that efficient transmitting antennas are short enough to mount on vehicles and handheld devices
• VHF signals propagate under normal conditions (excluding mountainous areas) as a near line-of-sight phenomenon:
  • approximate line-of-sight horizon distance in kilometers = sqrt(12.746 x antenna height in metres)
• used for:
  • Radionavigation 60: 84–86 MHz
  • FM radio broadcasting (VHF Band II: 88.1-108.1MHz)
    • some countries (Norway 2017, Switzerland 2024) have or are planning to, switch off FM radio services to be replaced by DAB+ digital services but historically DAB audio has not been as good as FM perhaps due to low bitrate broadcasts and portable receivers tend to use more power and DAB+ was actually shut down in Ireland and has had a relatively poor uptake in USA, Australia. As of 2025, there are no plans to switch off FM radio in Australia.
    • in Victoria:
      • ABC's FM transmitter at Marengo (serving the Apollo Bay area) operates at an Effective Isotropic Radiated Power (EIRP) of about 327 watts, which reflects typical FM broadcast power that is sufficient for regional coverage
      • see https://www.acma.gov.au/list-transmitters-licence-broadcast for listing or map of all licensed transmitters in Australia
      • unlicensed or low-power FM transmitters also exist but must comply with legal power restrictions, often much lower than 1,000 watts
  • “air band AM” air traffic control (108-137MHz)
    • aircraft still use AM to communicate with control towers, partly as more than one pilot could communicate urgently on the same frequency as others and still get heard, albeit perhaps garbled - since 2007 in Europe (and mandated in Europe from 2015 while the US still uses 25kHz channels), channels are often split into 3 parts, for a 25kHz channel, each part with 8.33kHz (requiring 8.33KHz radios), this reduces interference from multiple pilots
    • EPIRB homing signals use 121.5MHz swept tone AM analogue (broadcast to satellites on 406MHz though)
    • Fixed Maritime Mobile: 130–135.7 MHz
  • some weather image satellites
    • NOAA Weather (the last ones to use VHF, NOAA 15 and 19 were shut down Aug 2025) as well as Meteor-M satellites (Russian polar orbiters, M1 137.1, M2 series): 136-138 MHz generally 137.9MHz
  • amateur Ham radio (50-54MHz 6m band and 144-146MHz 2m band)
    • Automatic Packet Reporting System (APRS) packets
      • radio stations, Ham, and the International Space Station also send call sign and GPS location data on 144-145MHz depending upon region (Australia is mainly on 145.175 MHz)
      • data is carried over the AX.25 protocol at 1200 bit/s, typically sounding like old dial-up modem on the air
  • protected Astronomical Radio 150.8MHz
    • but a large number of LEO Starlink satellites are incidentally emitting radio at this frequency due to their onboard electronics and this is creating excessive noise⁴⁾
  • Fixed Aeronautical radio navigation: 160–190 MHz
    • ship and boat transponders use AIS on either 161.975 MHz (AIS 1, also known as channel 87B) and 162.025 MHz (AIS 2, channel 88B)
      • AIS signals containing call sign, GPS location data, heading and speed data are transmitted in bursts over these channels, with a bandwidth of 25 kHz, using Gaussian minimum shift keying (GMSK) modulation at 9600 bits per second
  • VHF digital TV broadcasting
    • VHF Band I (54-88MHz) was used for the transmission of analog television but this was completely switched off in Australia in 2013
    • Australia still uses DVB-T and not the newer DVB-T2
    • Melbourne digital TV uses VHF Band III:
      • SBS 184.5MHz
      • Nine 191.666MHz
      • ABC 226.5MHz
  • Digital Audio Broadcasting (DAB+) radio
    • 174–230MHz and can also operate in the L-Band spectrum (1452 – 1492 MHz)
    • National and commercial DAB+ services have been available in Australia since 1 July 2009
      • a 2011 review report concluded that DAB+ would have the potential to reach most of the population using a similar number of transmitters to the current FM services, but would struggle to match the coverage of high and medium powered AM transmitters that reach the remaining population
    • channel blocks:
      • 9A (202.928 MHz)
      • 9B (204.640 MHz)
      • 9C (206.352 MHz)
    • Melbourne broadcasts use 9A, 9C; Sydney use all three; Brisbane, Adelaide and Perth use 9B, 9C;
  • two-way land mobile radio systems (emergency, business, private use and military)
  • long range data communication up to several tens of kilometers with radio modems
  • Broadcasting Aeronautical Radionavigation: 255–283.5 MHz
  • Aeronautical Radionavigation AUS 49 / Maritime Radionavigation (radiobeacons) 73: 315–325 MHz
  • astronomical radio telescopes
    • Murchison Widefield Array (MWA) in Murchison, WA detect radio signals 70-300MHz (precursor of SKA-Low)
    • Australia's Square Kilometre Array (SKA) using Phased array dipole antennas at 500 sites in WA will detect radio signals 50-350MHz

• 300 – 3000 MHz with wavelength of 100–10 cm
• most of the ISM (Industrial, Scientific and Medical) bands are UHF
• propagate mainly by line of sight
• they are blocked by metal, trees, hills and large buildings although the transmission through building walls is strong enough for indoor reception.
• atmospheric moisture reduces, or attenuates, the strength of UHF signals over long distances, and the attenuation increases with frequency.
• occasionally when conditions are right, UHF radio waves can travel long distances by tropospheric ducting as the atmosphere warms and cools throughout the day.
• radio repeaters are used to retransmit UHF signals when a distance greater than the line of sight is required.
• antennae can be 2.5-25cm long and the short wavelengths also allow high gain antennas to be conveniently small.
• used for television broadcasting, cell phones, satellite communication including GPS, personal radio services including Wi-Fi and Bluetooth, walkie-talkies, cordless phones, CB radios
• UHF radar band
  • frequencies between 300 MHz and 1 GHz plus the L band between 1 and 2 GHz and the S band between 2 and 4 GHz
  • see radar and radar motion detector sensors for campers
• Cospas-Sarsat Search and Rescue EPIRBs 406MHz PSK digital
• standard license-free ISM bands used for remote control transmitters, etc
  • usually use either 315Mhz, 433MHz or 915MHz ISM bands
  • IoT and Meshtastic LoRa devices use 915MHz in Australia
• airplane transponders 1090MHz (ADS-B) - contains their call sign, GPS location, heading, speed, etc
• L band satellites
  • GPS transmits for civil use on L1: 1575.42MHz (higher precision GPS for advanced civil uses L5: 1176.45MHz)
  • emergency txt messages from smartphones:
    • uplink (sending signal from iPhone to satellite) operates around 1.6GHz (eg. Globalstar 1610MHz)
    • downlink (receiving signal from satellite to iPhone) can use the S band and sometimes higher frequencies such as 2.4GHz (Band 53/n53)
    • Zoleo uses Iridium uplink and downlink frequency: 1616MHz to 1626.5MHz
  • Inmarsat 3, 4 (“Alphasat”) and 6 satellites
    • Inmarsat Aero provides secure and reliable voice and data communication services for aviation 1530 MHz to 1660 MHz
    • Inmarsat-C STD-C EGC messages are emergency warning broadcasts sent via satellite to deliver critical safety and weather information to aircraft and ships.
      • 1545-1547 MHz in L-band for communications with aircraft
  • Elektro-L satellites - Russian geostationary weather satellites 1691-1693 MHz
• astronomical radio telescopes:
  • the Square Kilometre Array (SKA) using dish antennas in Sth Africa detect radio signals 350MHz-15.4GHz
  • Australian Square Kilometre Array Pathfinder (ASKAP) using 36 dishes in Murchison, WA detects 700MHz-1.8GHz
  • Molonglo Observatory Synthesis Telescope (MOST) using an east-west antenna near Canberra detects radio signals mainly at 843Mz but can detect 600MHz-1.2GHz
• in Australia - see top of this page
  • UHF citizens band CB 2-way radio: 476–477 MHz consisting of 80 channels
  • UHF digital TV 503 - 694 MHz
    • eg. Melbourne Channel 31 digital 557.666MHz
  • fixed point-to-point Link 450.4875 - 451.5125 MHz
  • land mobile phone service 457.50625 - 459.9875 MHz
    • Higher frequencies generally offer faster data transfer rates and lower latency, but lower frequencies provide better range and penetration, especially indoors or underground.
    • in Australia, 5G mobile uses various bands including low-band (700 MHz, 850 MHz), mid-band (2300 MHz, 3500 MHz), and high-band (26-28 GHz)
    • in Australia, 4G LTE mobile uses various bands including 700 MHz, 900 MHz, 1800 MHz, 2100 MHz, 2300 MHz, and 2600 MHz
    • in Australia, 3G mobile uses various bands including 850 MHz, 900 MHz and 2100 MHz - these were shutdown in 2024
  • mobile satellite service:
    • Iridium satellite phones in Australia use the 1.6GHz L band, specifically between 1616 and 1626.5 MHz
  • Wi-Fi operates at 2.4GHz (2412 MHz-2484 MHz) and 5GHz and new Wi-Fi 6E and 6GHz
  • Bluetooth operates at 2.4GHz

• 3 and 30 gigahertz (GHz)
• small wavelength allows them to be directed into narrow beams via parabolic dishes hence often used for data links
• propagate solely by line of sight;
• create strong reflections from metal objects the size of automobiles, aircraft, and ships, and other vehicles hence used in radar
• satellite services:
  • Inmarsat Aero and Inmarsat-C STD-C EGC emergency messages to aircraft can use 3.685-3.687 GHz as well as their usual L band 1530 MHz to 1660 MHz
  • NOAA weather X-band 8GHz
  • Himawari-9, a geostationary satellite operated by the Japan Meteorological Agency (JMA) which provides weather images to Australia's BOM on Ka-band (18.1–18.4GHz) - this may be relayed on 402MHz
    • HimawariCast (the rebroadcast of Himawari data for the Asia-Pacific region) is sent via DVB-S2 protocol on the C-band (approximately 3.7–4.2GHz)
  • Starlink satellites in Australia primarily use the Ku-band (12-18 GHz) for internet data and also use the Ka-band (26.5-40 GHz) for other purposes
• astronomical radio telescopes
  • the Square Kilometre Array (SKA) using dish antennas in Sth Africa detect radio signals 350MHz-15.4GHz
  • Australia Telescope Compact Array (ATCA) using six 22m dishes in Narrabri, NSW detect radio signals 300MHz-110GHz
  • Mopra Radio Telescope using one 22m dish in Coonabarrabran, NSW detect radio signals 300MHz-100GHz
  • Parkes Radio Telescope using one 64m dish in Parkes, NSW detect radio signals 700MHz- a few GHz
  • Ceduna Radio Observatory using one 30m dish in Ceduna, SA detect radio signals 1.2GHz – 23GHz
  • Mount Pleasant Radio Telescope using a 26m dish in Hobart detects 1.2GHz-23GHz

• low bandwidth digital HF radio modems can be used to send and receive emails, GPS, graphical weather bulletins and emergency communications globally
• this is not going to be used by a hiker as there is too much gear and nerdy computer configuration involved but may be useful for remote set ups
• https://www.sws.bom.gov.au/Educational/5/2/5
• Winlink is a free provider
  • you need to set up a Winlink HF Gateway which involves an amateur radio HF transceiver (could be software defined radio SDR), digital rig control interface, USB sound card, Windows based computer, and specialized Winlink control and modem software
  • in addition, as a Winlink Sysops you must be approved by the Winlink System Administrator before being allowed to connect to the Winlink network. This means you MUST have a Winlink account, be an active user of radio email, and be willing to setup dedicated hardware with backup power for the task.
  • see https://winlink.org/sites/default/files/RMSE_FORMS/winlink_hf_gateway.pdf

• see radio for campers

• see software defined radio (SDR) receivers
• these are great for learning radio and for detecting and analyzing non-audio data in particular that is being transmitted by radio waves
  • these include aircraft or ship transponders containing call signs and GPS location data, remote control devices, weather fax services, etc

• see radio for campers

• usually use a 100W transceiver
  • ICOM IC-7300
  • YAESU FTDX-10

• eg. Yaesu FC-40

• eg. ICOM IC-AH710 HF Broadband Folded Dipole - 80 Feet Long - 150 Watts

• see remote communication for campers and hikers

• these act like 2-way radios BUT they use cellular networks to send messages - NOT radio
• hence not very useful for remote campers without cellular network coverage