VHF and UHF Radio Monitoring

This page documents selected VHF and UHF radio signals that can be received with relatively simple SDR equipment. Unlike the permanently running reception systems on this website, these signals are mainly monitored and documented as examples of interesting radio services, signal types and decoding software.

The focus is on technically interesting signals: aviation voice and datalink systems, weather satellites, meteor scatter radar reflections, amateur radio satellites, AIS, DAB+ and other public or semi-public radio services. Some related systems, such as ADS-B, TinyGS and radiosonde reception, are covered on separate dedicated pages.

Reception and publication of radio signals may be subject to national regulations. This page documents signal characteristics, receiver setups and screenshots; no private or sensitive message content is published.

VHF Airband Voice

VHF airband voice is one of the most accessible monitoring targets above 100 MHz. Aircraft and ground stations use amplitude modulation, which makes the signals easy to recognize and receive with almost any SDR receiver.

Typical activity includes tower, approach, departure, area control, VOLMET, ATIS and aircraft-to-aircraft communications. From a good receiving location, aircraft at cruising altitude can be heard over long distances because of the line-of-sight propagation at VHF.

Signal type

Frequency range: 118.000–136.975 MHz
Modulation: AM voice
Channel spacing: 25 kHz and 8.33 kHz in many European allocations
Bandwidth: typically around 8–10 kHz for voice monitoring
Antenna: vertical VHF antenna, discone, ground-plane or airband antenna

Used software

SDR++, SDR#, GQRX, CubicSDR or OpenWebRX
Optional: rtl_airband for continuous multi-channel monitoring

Screenshot idea

Waterfall screenshot showing several AM airband channels with narrow vertical voice transmissions, plus an example of one tuned AM channel.

VHF ACARS

ACARS is an older aircraft datalink system used for short text-based operational messages between aircraft and ground stations. It is much slower than VDL Mode 2 but still useful as a simple introduction to aviation data decoding.

In Europe, activity depends strongly on location and current airline usage. ACARS is technically simple and can often be decoded with an RTL-SDR and a basic VHF antenna.

Signal type

Typical frequencies: around 131 MHz, depending on region
Common European channel: 131.725 MHz
Modulation: AM carrier with MSK data
Data rate: 2400 bit/s
Bandwidth: about 25 kHz

Used software

acarsdec
JAERO or other ACARS-capable tools where applicable
SDR receiver software for tuning and recording

Screenshot idea

ACARS bursts in the waterfall and a decoder window showing only non-sensitive technical fields, such as aircraft identifier, timestamp and frequency.

VDL Mode 2

VDL Mode 2 is now one of the most interesting VHF aviation datalink signals. It can be considered the modern, higher-speed successor to classic VHF ACARS. In Europe, VDL2 assignments are grouped in the upper part of the VHF aviation band, especially around 136.700–136.975 MHz, with 136.975 MHz used as the common signalling channel.

VDL2 transmissions appear as short digital bursts. With a suitable receiver and decoder, they provide a good example of modern packet-based aviation radio.

Signal type

Frequency range: typically 136.700–136.975 MHz in Europe
Common channel: 136.975 MHz
Modulation: D8PSK
Data rate: 31.5 kbit/s
Channel bandwidth: 25 kHz

Used software

dumpvdl2
vdlm2dec
SDR++ / SDR# / GQRX for tuning and spectrum display

Screenshot idea

Waterfall view of short VDL2 bursts on 136.975 MHz and a decoder terminal showing packet timestamps and technical routing information.

NOAA APT Weather Satellites — Historic Reception Example

For many years, the classic NOAA polar-orbiting satellites were among the most popular SDR weather satellite targets. Their APT transmissions produced low-resolution real-time cloud images around 137 MHz and could be received with very simple equipment.

This is now mainly a historic section. The legacy NOAA POES satellites NOAA-15, NOAA-18 and NOAA-19 have been decommissioned, so this part of the page is best used to show archived reception results and to document the former APT workflow.

Signal type

Former frequency range: 137 MHz satellite band
Modulation: analog FM APT
Image type: low-resolution weather image
Polarisation: RHCP preferred, but simple V-dipoles often worked surprisingly well
Bandwidth: roughly 40 kHz

Used software

SatDump
noaa-apt
WXtoImg, for historic setups

Screenshot idea

An archived low-resolution NOAA APT image, together with the recorded pass waterfall.

Note

This section should be clearly labelled as an archived or legacy example, not as a currently running live target.

Meteor-M LRPT Weather Satellites

The Meteor-M satellites are the most interesting continuation of 137 MHz weather satellite reception. Unlike the old analog NOAA APT system, Meteor LRPT is digital and can provide better image quality when the pass is strong and the decoder locks properly.

The currently relevant targets are Meteor-M N2-3 and Meteor-M N2-4. WMO lists real-time LRPT availability for Meteor-M N2-3, and Meteor-M N2-4 is listed in the active Meteor-M programme with LRPT frequencies in the 137 MHz band.

Signal type

Frequency range: 137 MHz satellite band
Typical LRPT frequencies: 137.1 MHz / 137.9 MHz / 137.9125 MHz, depending on satellite and current configuration
Modulation: digital LRPT, QPSK/OQPSK depending on satellite configuration
Bandwidth: about 100–150 kHz
Antenna: V-dipole, turnstile, QFH or crossed dipole
LNA/filter: useful but not always required

Used software

SatDump
Optional: older Meteor-specific demodulators and decoders

Screenshot idea

Meteor LRPT waterfall during a pass and the resulting RGB weather image from SatDump.

ORBCOMM Satellites

ORBCOMM is a low-Earth-orbit satellite system operating in the VHF range. The downlinks are in the 137–138 MHz band, close to the weather satellite frequencies, which makes them easy to notice while monitoring the 137 MHz satellite band.

For this website, ORBCOMM is interesting mainly as a spectrum and signal-identification example. The characteristic satellite passes, Doppler shift and burst structure make it a good demonstration of low-Earth-orbit VHF reception.

Signal type

Frequency range: 137–138 MHz downlink
Service: LEO satellite messaging / machine-to-machine communication
Modulation: digital burst transmissions
Reception: signal identification and spectrum documentation only

Used software

SDR++ / SDR# / GQRX
GNU Radio-based tools for experimental signal analysis
SatNOGS-style waterfall observation

Screenshot idea

A 137 MHz satellite-band waterfall showing ORBCOMM bursts during a pass, ideally together with visible Doppler drift.

GRAVES Meteor Scatter Radar

GRAVES is a French space-surveillance radar operating around 143.050 MHz. Although the radar transmitter itself is located in France, its signal can be received indirectly by forward scatter. Meteors entering the atmosphere leave ionized trails that briefly reflect the radar signal, producing short pings or longer bursts on the receiver waterfall.

This is one of the most visually interesting VHF monitoring targets because every meteor reflection becomes visible as a short trace in the spectrum. Strong meteor showers can produce a noticeably higher activity rate.

Signal type

Frequency: 143.050 MHz
Signal: continuous radar carrier
Reception mode: forward scatter reflections
Modulation: effectively unmodulated carrier for monitoring purposes
Bandwidth: very narrow; waterfall display over a few hundred Hz is useful
Antenna: small VHF beam or directional antenna, aimed for suitable forward-scatter geometry

Used software

Spectrum Lab
SDR++ / SDR# with waterfall display
Custom FFT logging scripts
RMOB-style meteor logging tools

Screenshot idea

Waterfall image showing several short meteor pings and one longer reflection trail.

ISS SSTV and Amateur Radio Satellites

The International Space Station and amateur radio satellites are among the most accessible space-related VHF/UHF targets. Some passes can be received with a handheld antenna, while more reliable results come from a small Yagi, crossed Yagi or azimuth/elevation tracking system.

ISS SSTV is event-based and usually not continuously active. When active, SSTV images have often been transmitted on 145.800 MHz FM. The current ARISS status page lists the ISS voice repeater on 145.990 MHz uplink and 437.800 MHz downlink, with APRS currently active on 145.825 MHz.

Signal type

ISS SSTV: 145.800 MHz FM during scheduled SSTV events
ISS APRS: 145.825 MHz packet/APRS when active
ISS voice repeater: VHF uplink / UHF downlink when active
Other satellites: VHF/UHF FM, SSB/CW transponders, telemetry beacons and APRS digipeaters
Doppler correction: important, especially on UHF downlinks

Used software

MMSSTV, QSSTV or RX-SSTV for SSTV
Dire Wolf for APRS / AX.25 packet
Gpredict, Look4Sat or SatDump for pass prediction
SDR++ / SDR# / GQRX for receiving
SatNOGS tools for telemetry-oriented reception

Screenshot idea

Received ISS SSTV image, satellite pass prediction window and SDR waterfall showing Doppler shift during the pass.

AIS — Marine Automatic Identification System

AIS is the VHF tracking system used by ships. It is more relevant near the coast or along large rivers, but it is technically very interesting and easy to decode. The two main AIS channels are 161.975 MHz and 162.025 MHz, each using 25 kHz bandwidth.

Depending on location and antenna height, reception may be limited inland. Still, AIS is useful as an example of a clean, structured VHF data signal.

Signal type

Frequencies: 161.975 MHz and 162.025 MHz
Modulation: GMSK
Data rate: 9600 bit/s
Bandwidth: 25 kHz
Antenna: vertical marine-band or wideband VHF antenna

Used software

AIS-catcher
rtl_ais
OpenCPN for map display
SDR++ / SDR# for spectrum view

Screenshot idea

AIS decoder output and a local map display showing received vessel positions, if available from the receiving location.

DAB+ Digital Radio

DAB+ is not a utility signal in the strict sense, but it is a useful VHF monitoring and SDR demonstration target. It occupies much wider bandwidth than the narrowband signals above and is a good test for SDR bandwidth, frequency stability and general receiver performance.

In Austria, DAB+ multiplexes are transmitted in VHF Band III. WorldDAB lists Austrian national and regional multiplexes, for example national blocks such as 5D, 8A, 6D and 5B, and a Vienna regional multiplex on 11C.

Signal type

Frequency range: VHF Band III
Typical DAB+ blocks: 5A–13F, depending on country
Bandwidth: about 1.536 MHz per DAB block
Modulation: COFDM
Content: digital broadcast radio and associated data services

Used software

welle.io
QIRX
DABlin
SDR++ / SDR# for spectrum view

Screenshot idea

Wideband waterfall showing a full DAB multiplex and a DAB decoder window showing ensemble and service information.

Existing Dedicated Pages

Some VHF/UHF monitoring systems are already documented on separate pages because they are operated continuously or have their own live-data workflow.

ADS-B

Aircraft position reception on 1090 MHz is covered on the ADS-B page. It includes the receiver setup, antenna system, feeder software and live aircraft map integration.

TinyGS

TinyGS satellite reception is covered separately because it is based on a dedicated LoRa ground station concept rather than a general-purpose SDR workflow.

Weather Balloons and Radiosondes

Radiosonde reception is covered on the radiosonde page, including SondeHub, rdzTTGOsonde or related receiver setups. Typical radiosonde activity is around 400–406 MHz depending on region and sonde type.

APRS

APRS reception and map integration can also be treated separately, especially if the station is already feeding APRS-IS or displaying live station data.

Equipment Used

Most of the signals on this page can be received with simple SDR hardware. The exact antenna is often more important than the receiver.

Typical SDR receivers

RTL-SDR Blog V3/V4
Nooelec NESDR
Airspy Mini / Airspy R2
SDRplay RSP series
HackRF for wider experimental bandwidths

Typical antennas

Discone for general VHF/UHF monitoring
VHF ground-plane for airband and AIS
V-dipole or QFH antenna for 137 MHz weather satellites
Small VHF Yagi for GRAVES meteor scatter
Handheld Yagi or crossed Yagi for amateur satellites
Dedicated 1090 MHz antenna for ADS-B
DAB Band III antenna for DAB+

Useful accessories

Low-noise amplifier for weak satellite signals
Band-pass filter for 137 MHz weather satellites
FM broadcast notch filter if local FM stations overload the receiver
Good coaxial cable and proper outdoor antenna placement
GPS-disciplined or temperature-stable SDR setup for long-term monitoring

Summary

VHF and UHF monitoring offers a wide range of technically interesting signals. Some, such as airband voice and DAB+, are easy to receive. Others, such as Meteor LRPT, ORBCOMM, GRAVES meteor scatter and amateur satellites, require more careful antenna choice, timing and software setup.

Together with the dedicated ADS-B, TinyGS and radiosonde pages, this section gives a broader overview of what can be received above the HF bands using small antennas, SDR receivers and open-source decoding software.