Category Archives: Aviation

Radio Waves: Maverick-603 SDR for FT8, EC-130J Commando Solo Final Broadcast, WRTH Survey, and Railways On The Air

EC-130J Photo By Staff Sgt. Tony Harp | An EC-130J Commando Solo aircraft from the 193rd Special Operations Wing performs a flyover during Community Days at the Lancaster Airport in Lititz, Pennsylvania, Sept.17, 2022. (Source: DVIDS)

Radio Waves:  Stories Making Waves in the World of Radio

Welcome to the SWLing Post’s Radio Waves, a collection of links to interesting stories making waves in the world of radio. Enjoy!


RadioStack’s Maverick-603 Is a Fully-Functional Open-Silicon Software-Defined Radio for FT8 (Hackster.io)

Built using open tools and readied for manufacturing at SkyWater using the Efabless platform, the chip on this SDR is something special.

New Hampshire-based RadioStack is looking to launch a piece of amateur radio equipment with a difference: the Maverick-603 is powered by free and open source silicon, built using the Efabless platform at a SkyWater fab.

“Maverick-603 is the first affordable FT8 receiver board built around an RF receiver chip that was designed using fully open source tools and fabrication,” its creators explain. “It is capable of acquiring FT8 signals between 7MHz and 70MHz. With this frequency range, you will be able to receive signals from around the world with high accuracy. The use of our Low Noise Amplifier (LNA) will also give the chip the ability to amplify very low-strength signals, which is necessary for an effective FT8 receiver.” [Continue reading…]

EC-130J Commando Solo performs final broadcast (DVIDS)

MIDDLETOWN, PA, UNITED STATES
09.17.2022
Story by Master Sgt. Alexander Farver
193rd Special Operations Wing

Airmen from the 193rd Special Operations Wing here, who operate the only flying military radio and TV broadcast platform in the U.S. military, transmitted their final broadcast today to spectators at the Community Days Air Show at Lancaster Airport, Lititz, Pa., bringing to close a 54-year chapter in unit history.

The EC-130J Commando Solo mission has helped keep this Air National Guard unit’s aircraft and its Airmen at the tip of spear for nearly every major U.S. military operation since the Vietnam War. Before bombs dropped or troops deployed in the Global War on Terror following the attacks on Sept. 11, 2001, this specially modified aircraft was already over the skies of Afghanistan broadcasting to America’s enemies that the U.S. military was bringing the fight to them.

“Any world event or crisis that our military has responded to in recent history, our 193rd Airmen – and Commando Solo – were likely key components in that response,” said Col. Eric McKissick, 193rd SOW vice commander. “As we prepare to open a new chapter in our history, we thank those who have enabled us to be among the very best wings in the Air National Guard.”
The genesis for this airborne information operations platform can be traced back to 1968 when the 193rd Tactical Electronics Warfare Group received its first aircraft, called the EC-121 Coronet Solo. In the late 1970s, the aircraft were replaced by the EC-130E before finally being replaced by the current aircraft in 2003. Throughout its history, it was instrumental in the success of coordinated military information support operations, earning the wing the moniker of “the most deployed unit in the Air National Guard.”

These deployments included: Operation Enduring Freedom, Operation Iraqi Freedom, Operations Odyssey Dawn/Unified Protector in Libya, Operation Inherent Resolve, Operation Resolute Support/Freedom’s Sentinel, Operation Secure Tomorrow and Operation Unified Response in Haiti.

Although this unique mission has earned the wing many prestigious accolades, Lt. Col. Michael Hackman, 193rd Special Operations Squadron commander, believes the mission’s success and legacy lies in winning the hearts and minds of adversaries and providing vital information to allies, refugees and victims in times of crisis.

“This capability has been an essential tool in our nation’s inventory, from the battlefields to assisting hurricane and earthquake-ravaged nations,” Hackman said. “During this time, thousands of Pennsylvania Air National Guard volunteers fulfilled their call to duty in this unique capacity, leveraging this capability against U.S. adversaries and supporting allies while always fulfilling the unit tenet of ‘Never Seen, Always Heard.’”

Aside from sporting an impressive operational record, the aircraft holds another distinction with having completed over 226,000 hours of accident-free flying.

“Having that many thousands of hours of accident-free flying is a testament to the excellence of our maintainers, to the operators and anybody who has touched that aircraft. Thank you for leaving that foundation and setting that example that we’re building from,” said Col. Jaime Ramirez, 193rd Special Operations Maintenance Group commander.

McKissick believes the success of the 193rd in operating the Commando Solo mission over the past few decades has led to Air Force Special Operations Command selecting the wing to be the first and only ANG unit to operate the MC-130J Commando II. The Commando II flies clandestine, or low visibility, single or multiship, low-level infiltration, exfiltration and resupply of special operations forces, by airdrop or airland and air refueling missions for special operations helicopters and tiltrotor aircraft, intruding politically sensitive or hostile territories.
“Today we honor the men and women, past and present, who have served this unit and mission with unparalleled distinction,” said McKissick. “The Airmen who came before us created an enduring culture and spirit of hard work, innovation and grit. We thank them for that, and we will do our best to carry this forward.”

The final broadcast of the EC-130J was transmitted to the ground and played at the Community Days Air Show at Lancaster Airport. In the transmission, the wing thanked the local community for their support over the past 54 years before broadcasting the Santo and Johnny song, “Sleepwalk.” The transmission ended with the phrase, “Commando Solo, music off.” [Read the full article here…]

WRTH Reader Survey

The new owners of the World Radio TV Handbook who like your input as readers. Please click on this link and share your opinions with them!

Railways On The Air (Southgate ARC)

The South Eastern Amateur Radio Group (EI2WRC) will be active from The Waterford and Suir Valley Railway station Kilmeaden, Co. Waterford for the ‘Railways On The Air‘ event on Sunday, the 25th of September.

WSVR is a community heritage project. The project has enabled the magic of rails golden age to be brought to life in Kilmeaden. A heritage narrow gauge railway runs along 17 kilometres of the abandoned Waterford to Dungarvan line.

The South Eastern Amateur Radio Group would like to thank the manager Maria Kyte and all the staff of The Waterford and Suir Valley Railway for all their help and allowing us access to the station to do this event again this year. For more information about the WSVR please see www.wsvrailway.ie .

The September meeting of the South Eastern Amateur Radio Group EI2WRC will take place on Monday, the 26th of September 2022 at 8.00 p.m. sharp at The Sweep Bar, Adamstown, Kilmeaden, Co. Waterford, Eircode X91 H588. New members or anyone interested in learning more about amateur radio or the group are as always very welcome to attend.

For anyone that wishes to find out more about the South Eastern Amateur Radio Group and their activities you can drop them an email to southeasternarg /at/ gmail.com or please feel free to go along to any of their meetings. You can check their website www.searg.ie and you can also join them on Facebook and follow them on Twitter.


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Ken reverse-engineers the Apollo spacecraft’s FM radio

Many thanks to SWLing Post contributor, Paul, who shares the following post from Ken Shirriffs’ Blog:

Reverse-engineering the Apollo spacecraft’s FM radio

How did NASA communicate with the Apollo astronauts, hundreds of thousands of miles from Earth? The premodulation processor1 (below) was the heart of the communication system onboard the Apollo spacecraft. Its multiple functions included an FM radio for communication to the astronauts, implemented by the Voice Detector, the module second from the top. In this blog post, I reverse-engineer the circuitry for that module and explain how it worked.

The Apollo communication system was complex and full of redundancy. Most communication took place over a high-frequency radio link that supported audio, telemetry, scientific data, and television images.2 NASA’s massive 85-foot dish antennas transmitted signals to the spacecraft at 2106.4 megahertz, an S-band frequency, giving the system the name “Unified S-Band”. These radio signals were encoded using phase modulation;3 onboard the spacecraft, a complex box called the transponder received the S-band signal and demodulated it.4

The voice and data signals from Earth were combined through a second layer of modulation: voice was frequency-modulated (FM) onto a 30-kilohertz subcarrier while data was on a 70-kilohertz subcarrier, so the two signals wouldn’t conflict.5 One of the tasks of the premodulation processor was to extract the voice and data signals from the transponder’s output. These voice signals went to yet another box, the Audio Center Equipment, so the astronauts could hear the messages from the ground. The data signals were decoded by the Up-Data Link, allowing NASA to send commands to the Apollo Guidance Computer, control onboard relays, or set the spacecraft’s clock.

Many systems worked together for communication, but I’m focusing on a single module: the voice detector inside the premodulation processor that performed the FM demodulation. [Continue reading the full article…]

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NavCanada decommissions LW and MW non-directional beacons

Photo by John McArthur via Unsplash

Many thanks to SWLing Post contributor, Markku Koskinen, who shares the following announcement from NAV CANADA:


NAVAID Modernization Program – Phase 6 National

NAV CANADA, the country’s provider of civil air navigation services, conducted an aeronautical study that reviewed the requirement for Non-Directional Beacons (NDBs) and Very-High Frequency Omnidirectional Rangefinders (VORs).

The study concluded that given the comprehensive radar surveillance coverage, and the propensity of area navigation (RNAV) with GNSS equipped aircraft, many navigation aids (NAVAIDS) are no longer required and should be decommissioned.

Where a current NAVAID identified in the study serves as an instrument approach aid or anchors an airway segment, NAV CANADA will ensure that a RNAV (GNSS) instrument approach procedure or RNAV airway segment is published, where required, before removal of the identified NAVAID.

Implementation is ongoing and will progress for the next several years. The sixth phase is represented below. Subsequent Notices of Change will be published for each upcoming phase.

Indicator – NAVAID Facility Name

YEA – Empress VOR
XD – Edmonton/Blatchford NDB
YHK – Gjoa Haven NDB
NL – St. John’s/Signal Hill NDB
ML – Charlevoix NDB
YPH – Inukjuak NDB
YKG – Kangiqsujuaq NDB
YXK – Rimouski NDB
YMU – Umiujaq NDB
YRR – Ottawa/Greely NDB
UL – Montreal NDB
OU – Quebec/Ste-Foy NDB
YLQ – La Tuque NDB
UFX – Lourdes-de-Joliette/St-Felix-de-Valois NDB
NM – Matagami NDB
YLA – Aupaluk NDB
VLV – St-Georges/Beauce VOR
YZA – Ashcroft NDB
LU – Abbotsford/Cultus NDB
QQ – Comox NDB
IB – Atikokan NDB
VC – La Ronge NDB
ZHD – Dryden/Barclay NDB
YL – Lynn Lake NDB
QW – North Battleford NDB
TH – Thompson NDB
ZTH – Thompson/Headframe NDB
BY – Beechy NDB
QN – Nakina NDB
YSB – Sudbury VOR
ZSB – Sudbury/Noranda NDB
YXI – Killaloe VOR
YSO – Simcoe/Lindsay (Kawartha Lakes) VOR

This change will take effect August 12, 2021 at 0901 Coordinated Universal Time (UTC). The appropriate aeronautical publications will be amended.

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Radio Waves: ATC Communications, ABC is Highly Trusted, New SW Forum in Turkey, and Did a Ham Speak To Crew Dragon?

Photo credits: NASA/Bill Ingalls

Radio Waves:  Stories Making Waves in the World of Radio

Because I keep my ear to the waves, as well as receive many tips from others who do the same, I find myself privy to radio-related stories that might interest SWLing Post readers.  To that end: Welcome to the SWLing Post’s Radio Waves, a collection of links to interesting stories making waves in the world of radio. Enjoy!

Many thanks to SWLing Post contributors Michael Bird, Seyfi Genç, and London Shortwave for the following tips:


Can you hear me now: How pilots communicate with ATC while 35,000 feet in the air (The Points Guy UK)

When you’re in a sealed, pressurised tube five miles above the ground, being able to communicate effectively is essential. In the early days of aviation, flags and light signals were used before designers were able to fit basic radio equipment into aircraft.

Modern aircraft now have an array of communication devices from the rudimentary HF radios of old to sophisticated satellite-based systems that enable us to talk almost as if we were on a mobile phone.

[…]The most common form of communication in aviation, very high frequency (VHF) radio calls are what we use for around 95% of our communications with ATC. In simplified terms, the transmitting station sends a signal that travels in a straight line and is picked up by the receiving station.

VHF comms provide clear voice communications. However, as the radio signals travel in straight lines, they are limited by the curvature of the earth and objects that they may come into contact with, such as hills and mountains.

The distance which a VHF signal can travel depends on both the height from which the signal is sent and the height of the receiving station. If both the sender and the receiver are on the ground, the distance will be relatively small. If both stations are in the air, the distance the signals can travel is much further.[]

Bushfire Research shows ABC Radio highly trusted and saves lives (Radio Info)

As the Bushfire Royal Commission continues, the ABC has released independent research that shows Australians turned to the national broadcaster in record numbers during the recent bushfire crisis.

The research shows that the ABC was the most trusted information source during the fires and that lives were saved as a result of people acting on information the ABC provided.

At the height of the bushfire crisis (31 December-14 January) ABC Sydney and ABC NSW local radio produced 296 hours of rolling/continuous fire coverage, ABC Gippsland 134 hours, and ABC Melbourne 83 hours.[]

New Shortwave Forum in Turkey

73 and hello from Shortwave Forum!

A dedicated Facebook and parallel Whatsapp group, to exchange news and info by SWL’s and DX’ers from Turkey, NOW goes wider and more permanent:

http://www.shortwaveforum.com

The Shortwave Forum will be open to all who want to join and contribute. Membership is free.

With members from all corners of the globe, the content of our beautiful hobby will reach the richness it always deserves.

Register now! And keep those tips and news coming!

Did a Ham Radio Enthusiast Actually Speak to Crew Dragon? (Popular Mechanics)

In a strange turn of events, a ham radio enthusiast in Gujarat, India falsely claimed to have made contact with NASA astronauts Bob Behnken and Doug Hurley during their historic journey to the International Space Station last weekend.

Engineer Adhir Saiyadh told the Ahmedabad Mirror he decided to try to connect with the ISS as it sped over India and “coincidentally got connected to their frequency and received a response from one of the commandants of the capsule,” he said.

But NASA says it simply isn’t true.

Behnken and Hurley blasted off from NASA’s historic Launch Complex 39A on Saturday, May 30. After 19 hours in orbit, the astronauts docked with the ISS and reunited with fellow astronaut Chris Cassidy—whose ham call sign is KF5KDR, by the way—and Russian cosmonauts Anatoly Ivanishin and Ivan Vagner.

“We did check with SpaceX to confirm that they were not aware of any communication with the astronauts via ham radio, and the crew did not report having received communication,” a NASA spokesperson told Popular Mechanics via email. “We are also under the impression that may be technically impossible for the Crew Dragon to communicate through ham radio.”[]


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Live Frequencies for HF ATC Traffic

Many thanks to SWLing Post contributor, Dan Van Hoy (VR2HF), who writes:

Like many, I enjoy listening to HF ATC traffic, all on USB, of course. I’ve been doing it since my teen years. Recently, I discovered ARINC posts live frequencies on their Webpage for both the Atlantic and Pacific. The pages will need to be refreshed to get the latest changes:

No more guessing or searching around. Enjoy!

Wow!  Thanks so much for the tip, Dan! I, too, love listening to HF ATC traffic and will bookmark both of these pages. If you’re new to HF ATC monitoring, note that all of these frequencies are in SSB (Single Side-Band).

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The Sporty’s Air Scan II has a unique “Aviation Interrupt” feature

Many thanks to SWLing Post contributor and supporter, Mario Filippi (N2HUN), who writes:

Hope you are doing well, am really enjoying the SWLing Post, it’s my daily version of the New York Times for the radio hobbyist. I realize that this is not SW related but did you know there is an unusual aircraft scanner sold by Sporty’s Pilot Shop?

The AirScan II is an AM/FM/VHF air band scanner.

Beauty of it is you can listen to your favorite AM or FM broadcast while it scans your favorite air band channels, then it’ll interrupt the broadcast when it finds an active channel.

https://www.sportys.com/pilotshop/air-scan-ii-radio-with-aviation-interrupttm.html

I think it’s an excellent idea. I’ve purchased from Sporty’s in the past, they are excellent. Keep up the good work Thomas and 73’s.

Thank you for the tip, Mario! That is a brilliant feature–especially for aviation monitoring. This little scanner also has some bluetooth functionality, so you could connect your smartphone, tablet, or PC to it, play your favorite recordings, and it would also interrupt the Bluetooth audio for aviation traffic. Very cool.

Reviews say that air band sensitivity is mediocre, but I bet with an external antenna, it would be improved.  As you say, Mario, Sporty’s has an excellent reputation as an aviation retailer.

And thanks for the kind compliments about the SWLing Post!

Please comment if you own or have used the Sporty’s Air Scan II!

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Guest Post: Decoding Inmarsat L-Band AERO and STD-C messages using the SDRplay RSP SDR

Many thanks to SWLing Post contributor, Mike Ladd (KD2KOG), who shares the following guest post. Note that the following tutorial is also available as a PDF (click here to download).


Basics to decoding Inmarsat L-Band signals using the RSP SDR

by Mike Ladd

Note: CHECK WITH YOUR LOCAL LAWS BEFORE DECODIING ANY SIGNALS FROM THE INMARSAT SYSTEM

Hardware used

SDR: RSP1a SDR from SDRplay? https://www.sdrplay.com/rsp1a/

Antenna: Modified GPS patch antenna for L-Band from SDR-Kits, model A154.? https://www.sdr-kits.net/L-Band-Receive%20Antenna

Software used

SDRuno v1.32
https://www.sdrplay.com/downloads/

VBcable (Donationware) vPack43
https://www.vb-audio.com/Cable/

VAC (Paid for use) v4.60
https://vac.muzychenko.net/en/

JAERO (Free) v1.0.4.9
https://github.com/jontio/JAERO/releases

Tekmanoid STD-C Decoder (Paid for use) v1.5.1
Requires Java JRE, check your local laws before using this decoder.
http://www.tekmanoid.com/egc.shtml

https://www.java.com/en/download/

Introduction

(some text taken and edited from the RTL-SDR Blog website)

This document is not a definitive guide to Satcom, L-Band transmission or the Inmarsat system. This is a collection of information that I have found scatter throughout the internet and re-compiled into a document, this document. My aim is to help you get started and hopefully guide you in the right direction. Expect typographical mistakes, inaccuracies, or omissions

Inmarsat is a communications service provider with several geostationary satellites in orbit. Inmarsat provides services such as satellite phone communications, broadband internet, and short text and data messaging services. Geostationary means that the Inmarsat satellites are in a fixed position in the sky and do not move.

The Inmarsat 3-F(x) satellites have transponders transmitting data in L-Band (1.5 GHz) that can be decoded. 

The modes we will cover in this document are Aeronautical (Classic Aero or ACARS) and Inmarsat-C (STD-C) using an RSP1a, RSP2/2pro or RSPduo connected to the SDR-Kits modified L-Band patch antenna. The Inmarsat system is not limited to only these types of networks. We are limited to the decoders available.
https://en.wikipedia.org/wiki/Inmarsat

Some regions that use the I-3 satellite services moved and migrated to the Inmarsat I-4 Satellites.  See the following document.  https://www.inmarsat.com/wp-content/uploads/2018/09/INM_C_I3_I4_migration_guide_V3.0.pdf

Two of the most popular decoding applications are JAERO used for ACARS and Tekmanoid STD-C Decoder used for decoding STD-C NCS transmissions on the Inmarsat 3-F(x) satellites

https://www.sigidwiki.com/wiki/Inmarsat_Aero

https://www.sigidwiki.com/wiki/Inmarsat-C_TDM

Software installation

Virtual Audio Cable: A virtual audio cable allows you to pipe audio from application (SDRuno) into another application (a decoder like JAERO) digitally. I will assume SDRuno is already installed with your device attached and functioning properly. 

You can now download a virtual audio cable package.  If you already have a virtual audio cable package installed, you can skip to the next section. If you don’t have a virtual audio cable application installed, you only need to choose one and only install one of the two, either one works fine

Close any running apps, install the virtual audio cable and reboot your computer. When your computer boots back to your desktop, your computer will now have a virtual audio cable pair installed on the system. 

You can verify by going to your Control Panel and double clicking the Sound icon. VB-Cable and Virtual Audio Cable will only install a single virtual audio cable pair, one is for the input (Recording) and one is for the output (Playback). A single pair is all that is needed (as shown below).

JAERO

(some text taken and edited from the JAERO website)

JAERO is a program that decodes ACARS (Aircraft Communications Addressing and Reporting System) messages sent by satellites (in this case Inmarsat) to Airplanes (SatCom ACARS). This is commonly used when airplanes are well beyond VHF range. 

JAERO also allows for decoding and demodulation of voice calls, due to local laws and privacy, I will not show or discuss how to do this. You can find more information about that JAERO feature online.

JAERO can be downloaded from the link provided on the first page of this document. After downloading the installer, simply double click the setup file and install it on your primary drive.

Tekmanoid STD-C Decoder

(some text taken and edited from the USA-Satcoms website)

Inmarsat STD-C is a data or message-based system used mostly by maritime operators. An Inmarsat C terminal transmits and receives on L-Band to various geosynchronous satellites that service each major ocean region. 

The Tekmanoid STD-C decoder will decode STD-C Inmarsat EGC (enhanced group call) and LES (land earth station) messages. Some of these messages contain private information. Reception of these messages may not be legal in your country; therefore, your local laws should be checked.

The Enhanced Group Call (EGC) service is a message broadcast service with global coverage (except the poles) within the Inmarsat-C communications system. Two of the services provided are:

FleetNET and SafetyNET

FleetNET is used to send commercial messages to individuals or groups of subscribers (for example, individual companies communicating with their own Mobile Earth Stations (MES). SafetyNET is used for broadcasting Maritime Safety Information (MSI) such as Navigational warnings, meteorological warnings, meteorological forecasts and other safety related information (including Distress Alert Relays) from official sources.

The LES station acts as an interface (or gateway) between the Inmarsat space segment and the national/international telecommunications networks. 

The Tekmanoid STD-C decoder requires Java JRE in order to run. The link for the Java runtime environment is on page 2 of this document. For information contact the developer direct [email protected]

There are alternatives to using the Tekmanoid STD-C decoder, but in my opinion the other decoders available do not perform as well on low end systems or even work without needing “helper” applications to be installed. Tekmanoid STD-C decoder is very easy to use and works great on my low-end system using minimal system resources.

Putting all the pieces together

ACARS and STD-C messages will transmit via the Inmarsat satellite deployed within your coverage area/region, you will need to choose the Inmarsat satellite that is closest to your coverage area. 

Note that only different frequencies are used between ACARS transmissions and STD-C transmissions. You will only need to receive from one of the available 3-F(x) Inmarsat satellites. 

L-Band ACARS transmissions are in the 1.545 GHz range but STD-C messages are on fixed frequencies (shown on page 8)

Since STD-C transmissions are broadcasted on fixed frequencies, we want to monitor the TDM NCSC channel, again these are fixed for the following Ocean Regions. Choose the region closest to your location (page 9).

Again, some regions that use the I-3 satellite services moved and migrated to the Inmarsat I-4 Satellites.  See the following document.  https://www.inmarsat.com/wp-content/uploads/2018/09/INM_C_I3_I4_migration_guide_V3.0.pdf

STD-C transmissions are broadcasted on fixed frequencies, NCSC channel. The NCSC frequency per region is noted below.

Inmarsat satellite: Inmarsat-4 F3 (AOR-W)
Direction: 98° West
Frequency: 1.537.70 GHz

Inmarsat satellite: Inmarsat-3 F5 (AOR-E)
Direction: 54° West
Frequency: 1.541.45 GHz

Inmarsat satellite: Inmarsat-4 F1 (IOR)
Direction: 25° East
Frequency: 1.537.10 GHz

Inmarsat satellite: Inmarsat-4 F1 (POR)
Direction: 143.5° East
Frequency: 1.541.45 GHz

I will assume you have located the Inmarsat satellite that covers your region. I suggest using a compass on your mobile phone to pinpoint the general direction. The direction is in ° (degrees). I am referencing true north, not magnetitic north (traditional analog compass). https://en.wikipedia.org/wiki/Magnetic_declination

You can also download an app for your smartphone called Satellite AR (Android and IOS). After you locate the correct direction of the Inmarsat satellite, you will want to place the L-Band patch on a flat metal surface. I have read that the receive pattern of this patch antenna is z (about 85-90°, straight up). Point the top of the antenna facing the Inmarsat satellite. Using the roof of my car worked just fine, just remember to point the front of the antenna at the satellite.

https://www.u-blox.com/sites/default/files/products/documents/GPS-Antenna_AppNote_%28GPS-X-08014%29.pdf

Launch SDRuno and click the PLAY button, remember that if the RSP(x) is in ZERO IF mode, give frequency separation between the VFO (top frequency) and LO (bottom frequency). In LOW IF mode this is not needed. I suggest running a sample rate of 2 MHz, larger bandwidths are not needed. 

The SDR-Kits patch antenna requires that the RSP(x) Bias-T be enabled. The Bias-T option is enabled within the MAIN panel of SDRuno. See the SDRuno manual located here. https://www.sdrplay.com/docs/SDRplay_SDRuno_User_Manual.pdf view page 17.

With the Bias-T enabled. Set the RSP(x) RF GAIN to max. The RF GAIN slider is located on the MAIN panel. See the SDRuno manual located here. https://www.sdrplay.com/docs/SDRplay_SDRuno_User_Manual.pdf view page 17.

For more information about the RF GAIN settings of the RSP(x)
https://www.sdrplay.com/wp-content/uploads/2018/06/Gain_and_AGC_in_SDRuno.pdf

Select the Virtual audio cable as the output in SDRuno, this is selected via the RX Control panel. SETT. button and clicking on the OUT tab.

Have SDRuno’s Volume slider (RX Control) at about 35-40%

Upper sideband is recommended but I found the best mode to use for L-Band ACARS or L-Band STD-C decoding is DIGITAL with a filter width of 3k. 

Be sure to set a proper step size (right click the RX Control frequency readout). The step size is not important for STD-C transmissions because these signals are only on one frequency for the satellite in your region but L-Band ACARS signals will be on many frequencies. Setting the proper step size will avoid issues when you point and click on signals you want to decode using the JAERO decoder.

You will want to center the signal with a little breathing room within the AUX SP filter passband. The filter slopes are very sharp. Keep the signal centered and away from the extreme edges (red markers). 

Select your virtual audio cable within the decoder’s audio input preferences.

The Tekmanoid STD-C decoder sound properties are located under Settings in the toolbar menu.

JAERO’s sound settings is located under the Tools menu and Settings.

For STD-C decoding use the frequency from page 8 of this document, remember we only want to monitor the TDM NCSC channel in the Tekmanoid STD-C decoder.

For JAERO decoding, I suggest you start in the 1.545 GHz portion and observe the constellation in the JAERO decoder. 

The signal to noise ratio (SNR) needed for successful decoding in these decoders will need to be greater than 7dB. When working with a weak satellite signasls, try decimating the signal using SDRuno’s decimation feature. (MAIN panel, DEC).

Click here to view on YouTube.

Additional resources

Videos:

Click here to view on YouTube.

Click here to view on YouTube.

Click here to view on YouTube.

Click here to view on YouTube.

SDRuno:

L-band frequency bank
https://mega.nz/#!jRFRiSaA!CcmRRRpjToxPzyGV9bf7MkDkKnqCYZCwwjC5curWj6g

PDFs:

https://www.inmarsat.com/wp-content/uploads/2018/08/Aero_Service_External_Com_Kit_I3_to_I4_Transition_21AUG2018.pdf

http://seaworm.narod.ru/12/Inmarsat_Maritime_Handbook.pdf

Websites:

https://usa-satcom.com/

https://uhf-satcom.com/

I hope this document helps you get started decoding Inmarsat L-Band transmissions from the I3-F(x) satellites. I am sure I missed some key features, remember this is only a primer/basics to decoding these types of transmissions.

Warmest of 73,
Mike-KD2KOG


Many thanks for sharing your tutorial here on the SWLing Post, Mike! This looks like a fascinating activity that really requires little investment if one already owns an RSP or similar SDR. I’m certainly going to give L-Band a go!  Thank you again!


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Your support makes articles like this one possible. Thank you!

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