Category Archives: Videos

Guest Post: Martin tours Radio Voz Missionária in Brazil

Many thanks to SWLing Post contributor Martin Butera for the following guest post:

Photo: Martin Butera, at the entrance door of the station.

Report and research by: Martín Butera

Photographs and Video by: Ligia Katze

Photo edition: Mark Van Marx (Marcos Melzi)

Table of contents

1. Introduction (Brief History of the Radio Voz Missionária ).
2. Interview with Luiz Carlos Machado (Chief Radio Station Coordinator)
3. Interview with Hueslen Santos (vice-president of Gideões Missionários)
4. Study and Technical Control
5. Radio links
6. Field of Antennas and Transmission Lines
7. Transmitter room
8. Final conclusions
9. Acknowledgments
10. About the author


1. Brief Introduction to the History of Radio Voz Missionária

Rádio Voz Missionária transmits from the studios located in Camboriú – SC – Brazil.

(GPS coordinates) 27º01’36.18  S 48º38’53.33  0.

The station belongs to “Last Minute Missionary Gideons”, also known as GMUH–the largest Pentecostal Protestant missionary organization in Brazil–and its main objective is to spread the gospel of Christ in Brazil and throughout the world.

The Last Minute Missionary Gideons were born in the late 1970s, by the hand of the Brazilian Gospel Minister Cesino Bernardino.

Since that time the number of believers has grown day by day.

They carry an important social action, in the Amazon region, with several ships, especially with a clinical-dental ship, called Gideão VI.

They also build shelters for children in northeastern Brazil and primary schools in the countries of Haiti and Peru.

Also, they have drilled wells in desert regions of Africa and northeastern Brazil, they have a mobile hospital, with doctors specialized in different areas such as cardiologist, dentist and clinicians in general with their own ambulances, all achieved thanks to the contribution of their faithful who believe in the project and thus give free assistance to the most needing, arriving in this way not only with the word of the gospel, but also with direct actions.

Cesino Bernardino

Cesino Bernardino (Imbituba, November 29, 1934 – Blumenau, July 30, 2016), was a Brazilian Gospel minister, teacher and writer. He was president of Last Minute Missionary Gideons Brazil.
Cesino Bernardino entered the history of the Brazilian evangelical church, being one of his greatest missionaries, not only in the farthest corners of Brazil, as well as in underserved regions of the planet such as Cuba, Haiti, Easter Island and remote areas of the African continent.

Cesino Bernardino teaches that you never have to give up dreaming, especially when your dreams fit God’s purposes.

In March 2012, he was nominated for a Nobel Peace Prize.

2. Interview with Luiz Carlos Machado (Chief Radio Station Coordinator)

Without a doubt, radio is one of the main communication vehicles that exists. Luiz Carlos Machado is a passionate radio director with more than 50 years as a professional in the field.

Luiz Carlos Machado is in charge of this great communication structure, which is “Rádio Voz Missionária”, since its inception, for more than 30 years.

Luiz Carlos Machado has always been linked to the shortwaveradio. Among the many radio stations where he’s worked, and the most important for him were, the shortwave radio station called “Rádio Diário da Manhãna Ltda”, located in the neighboring city of Florianopolis and an outstanding radio station “Radio Marumby” of the city of Curitiba.

To mention Marumby radio is to talk about one of the most respected evangelical radio stations in all of Brazil, with its signals in modulated amplitude, shortwave and tropical.

Working on Marumby radio, he met Bishop Cesino Bernardino, who was doing his evangelical programs at that station.

A few years later Luiz Carlos Machado, was invited by Cesino Bernardino to direct the radio station “Voz Missionária” in the city of Camboriú.

Photo: Martin Butera in the office of Luiz Carlos Machado (Chief Radio Station Coordinator).

MB: What was it like to make the decision to transmit on the shortwaves and not on AM or FM. Which would be much cheaper?

LCM: That decision was taken from the beginning by a very broad vision of the president of the Gideões, Cesino Bernardino. He was very clear that the word of God, had to reach the most remote places and knew that through the AM and FM, would be limited.

He always knew the high cost of maintaining 3 shortwave transmitters in this case, without advertising, only with voluntary contributions, seeing today the entire structure that “Rádio Voz Missionária” built, without a doubt it is a miracle of God, manifested in the faith of our president.

MB: Technically speaking, what can you tell us about your transmissions?

LCM: The radio station transmits 24 Hs with 10 Kilos and at night the power is reduced to 5 kilos, the three transmitters are of national manufacture those of 31 Mts and 49 Mts, are from a factory that is in the city of Sao Paulo, called Prestec and the 25 Mts, is from a company in the city of Porto Alegre called BT.

MB: And what can you tell me about the antennas?

LCM: The antennas are something that we have to improve a little, although we have a lot of height, because they are located on a mountain. The antennas we have are half wave dipoles, one for each band and they are not very high in ration to the floor of tower.

Saying that, as I mentioned, we have height in the mountains and are pointed towards the sea that we are very close to, taking advantage of propagation.

MB: How is the relationship with other platforms like the internet?

LCM: The radio is highly linked to all the digital platforms of the moment, both in audio and online video streaming, through applications and websites, updated at all times, but our priority is always the shortwave.

MB: Many DXers who are reading this report now, are asking about the delay on the responses of their reception reports, is this something that interests the station?

LCM: Yes, of course, that we are interested in receiving QSLs and more, while we are here doing this interview, I can show you that today I received correspondence with reception reports from very different countries in Japan, Canada and Australia.

Previously we confirmed with a nice certificate all the reports, now a while ago that for a matter of time we are not doing it, but we ask for your patience that we will confirm all the reports, you can write to: Joaquin Nunes, 244 Centro – Camboriú, SCCEP 88340-371, Brazil.

MB: What is it like to produce 100% religious programming?

LCM: It is something with a lot of responsibility is to touch the hearts of many people with the message of salvation in Jesus Christ.

It is not an easy task, to produce a contemporary and professional programming, to present the message of Jesus Christ, our commitment is not only directed among believers, but also in the general population. We want to have a biblical, educational and cultural program that, due to the quality of its programs, equipment and personnel, becomes increasingly heard.

MB: Any final words?

LCM: I just have to thank you for being here, interested in the “Queen of the Air”, as this station is known. I personally feel that this radio work became divine for me and I am excited to know that many people accepted Christ from this radio, thus making a difference in their hearts.

God bless you brother Martin!

3. Interview with Hueslen Santos (vice-president of Gideões Missionários)

I was very well received in the studies of the radio station where the vice-president of Gideões Missionários, the preacher Mr. Hueslen Santos, is waiting for me and we talked a little about the activity they carry out.

Photo: Martin Butera with Hueslen Santos (vice-president of Gideões Missionários).

MB: Who are the Last Minute Missionary Gideons?

HS: Last Minute Missionary Gideons, also known as GMUH based in Camboriú, Brazil, is the largest Pentecostal Protestant missionary congress in Brazil and its main objective is to spread the gospel of Christ in Brazil and in the world.

MB: What do members of Last Minute Missionary Gideons believe?

HS: We believe that there is only one way and it is called “Jesus Christ”, but we are aware that we cannot reach a lacking place, where people are hungry and just talk about the gospel, we have to do much more. The social action is developed with the vision of Jesus, the first was concerned with the restoration of the soul by applying the divine word, but then Jesus was orienting the disciples to feed the people. So what we do is evangelism and social action.

MB: I know that social projects are a lot, but if you had to list a couple, what would they be?

HS: All projects are exciting and very important, we have more than 40 distributed between Brazil and the rest of the world, maybe today I can mention two that are very revealing to me.
One is the Gideões Clinic ship, a missionary project in the great Amazon that began more than 34 years ago, initially preaching the gospel and then preparing, sending and maintaining missionaries both in the cities and in the countryside.

In the immensity of the Amazon, where the largest river basin in the world is located, the ship dictates the rhythm of life. Missionaries use boats as their main means of transportation, as the Amazon River connects hundreds of small riverside communities, small towns, larger municipalities and large capitals.

The work of evangelism and social action is a great challenge in this region. On the banks of the Amazon rivers there are people without life prospects, living in extreme poverty, isolated in the middle of the forests, people lacking medical services and sanitation, and most of them have never heard of Jesus Christ . For them, Missionary Gideons Last Minute boats are the only form of help and assistance.

Another exciting project is that of Haiti, for almost more than 19 years, Last Minute Missionary Gideons have been developing activities in education, providing education to approximately five hundred children.

Through their own school, students receive daily education, food, and are also evangelized by teachers about the word of God.

MB: Any final notes?

HS: First, I wanted to thank you for coming to our station to do your job.

We live in a world in despair and the only way to end that despair is the word of Jesus that is love in action.

Our missionaries will not lower their arms, carrying the gospel from north to south, from east to west, in the farthest reaches of the earth.

The Last Minute Missionary Gideons, we know that it is time to pray with our hearts and work with our hands.

Photo: Gideão VI ship.

Photo: Hueslen Santos (vice-president of Gideões Missionários), in Haiti.

4. Studio and Technical Control

The radio has a studio and a technical control center divided in the classical way, separated by an acoustic glass, making eye contact with the operator.


The studio is very large, something fundamental so that you can work comfortably, it has a specially designed table, equipped with 6 Behringer  condenser microphones and very good chairs, to work comfortably and well relaxed, maintaining a good body posture.

The walls and door of the studio are totally isolated from outside noise, with acoustic panels.

Studio Control

The control room is a simple of space, but well-designed to control various studio activities like live broadcasts and recordings (although not at the same time, because there is a single cabin).

Equipped with all the basic elements, such as: computers with radial automation software, sound console, audio processors, talkback microphone (to maintain communication between the studio and the operator through the headphones, without letting the communication air), monitors and even CD compact disc readers, something very nice to find that still in a station, the radio maintains an interesting disco.

Video, view of the technical control.

Photo: Martin Butera, in control of the Rádio Voz Missionária

Photo: Martin Butera, next to the wall of CDs.

5. Radio Links

The system is located in a tower, very close to the entrance of the station.

It is a tower of about 30 Meters, with a Yagi antenna in the middle of the tower, the link connects the studios, to the antennas of the “Morro das Anenas” with a classic point-to-point system.

This tower is shared by a community FM station, also of the group “Gideões Missionários da Last Hora”, called Rádio Paz no Vale 105.9 FM.

It can be seen in the photographs at the top of the tower along with two dipoles of the Jampro type of said station.

Photo: Radio links “Rádio Voz Missionária”, you can see at the top of the tower two dipoles of the Jampro type, belonging to the community radio station Rádio Paz no Vale 105.9 FM.

Photo: Martin Butera, next to the “Rádio Voz Missionária” link tower, you can see the Yagi antenna of the point-to-point system.

Photo: Angel Lana Arpon (Martin’s logistics assistant) and Martin Butera at the entrance of the neighboring radio station, “Rádio Paz no Vale 105.9 FM”.

Photo: station entrance, the protection of the link tower can be seen.

6. Antenna field and Transmission Lines

The antennas and transmitters are located at the top of the “Morro das Anenas” (GPS coordinates 27º02’24.48  S 48º39’17.27  0).

“Rádio Voz Missionária” Antenna Field, Camboriu Brazil – Exclusive Drone Footage


The tidy field of antennas has a set of 3 dipole antennas designed for high-power transmissions.

Photo: Zeppelin antennas for the various work bands.

Photo: End of two Zeppelin antennas used by the broadcaster for different bands.

Photo: Rhombic antenna system for Tropical Bands.

Transmission Lines

Since each antenna is powered separately, each has its own transmission line. In the photographs we can see that they are bifilar lines of the cage type.

Photo: Detail of the output of the transmission lines of the coupler box

Photo: Coupling system of one of the antennas.

Photo: Box where the coupler for the 31M band is housed.

Photo: Box where the coupler for the 49M antenna is housed.

Photo: Martin Butera next to the box where the coupler for the 25M band is housed.

7. Transmitter room

They are three Brazilian national solid-state industry transmitters, prepared for DRM transmission and operating at 10,000 watts of power on 25M (11,750 kHz), 31M (9,665 kHz) and 49M (5,940 kHz).

Photo: Martin Butera and Luiz Carlos Machado, at the door of transmitter rooms.

Photo: 31 Mts and 49 Mts transmitters.

Photo: Martin Butera next to the 31 Mts transmitter.

Photo: Martin Butera and Luiz Carlos Machado, in the link racks and audio processors

Photo: link racks and audio processors

8. Final conclusion by Martin Butera

Writing about the fact that international shortwave stations are losing relevance to the foreign policy objectives of many governments would not be a novelty.

We all know that maintaining high-power shortwave stations is very expensive and many countries know about this, so they are implementing austerity programs and cutting their budgets.

Then the vast majority of international broadcasters end up opting out of on-air transmissions and streaming on the internet. A few, however, still maintain an on-air presence although in a rather “testimonial” way.

Then the question arises: why is shortwave currently mostly occupied by religious stations?
The answer, I think, has been addressed in this report. Shortwave still maintains a place of importance, for religious stations, because they know that in the vast majority of places where they want to reach with their religious message and action, the Internet It is not available to most citizens. Even if some of their audience has Internet access, it is very limited.

Shortwave is practically the only contact channel, which is available to reach these populations with their message.

With shortwave, you may not have a massive or profitable audience, for these stations. But it still has the most faithful listeners of the spectrum and that is a value, which they know very well what religious stations are all about.

9. Thanks to Martín Butera

I dedicate, thank and congratulate all the missionaries of “Gideões Missionários da Last Hora”, for the tremendous work they do helping people find their spiritual path and assisting them directly with food, health, clothing, education and much more.

Thanks to the gentlemen: Zilmar Miguel (President), Hueslen R. Santos (Vice-President) and the kind Luiz Carlos Machado (station coordinator)

To my wife, Ligia Katze (in photographs).

To my dear friend Angel Lana Arpon (PP5GEL), for assisting me in logistics.

To my friend Ivan Dias da Silva Junior, Director of the Regional DX – Sorocaba-Sao Paulo- Brazil, who collaborates in Portuguese translations and publishes this material in the form of a micro book, for the club and directs

Finally, my friend Thomas Witherspoon, director of SWLing Post, for publishing this report completely and collaborating in this way for the world of radio.

Photo: Martin Butera and Angel Lana Arpon at the door of the station.

Photo: Hueslen R. Santos (Vice-President), Zilmar Miguel (President), Martin Butera and Luiz Carlos Machado (Coordinator of the station).

10. About the author

Martín Butera is a shortwave radio listener and has been an amateur radio operator since 1992. Martin  has participated in DXpeditions throughout South America, with the Argentine radio callsign LU9EFO and the Brazilian callsign PT2ZDX.

Martin is a correspondent journalist from South America for the British DX Club’s magazine, Communication. If you would like to be a member of the Briitish DX Club, you can find information here

Martin is the founder of CREW called 15 point 61 (15.61), são paulo – Brazil.

Martín Butera is a journalist, documentary filmmaker and founding member of Radio Atomika 106.1 MHz (Buenos Aires, Argentina)

He currently lives in Brasilia, capital of Brazil.

Thank you for another fine report and fascinating look into the world of South American shortwave broadcasting, Martin! I love tuning in Radio Voz Missionária. It’s so nice to see what’s on the other side of the signal!

Click here to read other station reports by Matin Butera.

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Restoration of a USN version of the ARC-5 command set receiver

(Source: Southgate ARC)

Gregory Charvat N8ZRY writes on Hackaday about an un-modified-since-WW2 surplus CBY-46104 receiver with dynamotor.

He writes:

I’ve been told all my life about old-timey Army/Navy surplus stores where you could buy buckets of FT-243 crystals, radio gear, gas masks, and even a Jeep boxed-up in a big wooden crate. Sadly this is no longer the case.

Today surplus stores only have contemporary Chinese-made boots, camping gear, and flashlights. They are bitterly disappointing except for one surplus store that I found while on vacation in the Adirondacks: Patriot of Lake George.

Read the full story at


Video description: Repair and restoration of a USN version of an ARC-5 command set receiver. This model covers 1.5-3 Mc, runs off its original dynamotor, with no internal circuit modifications. This radio is original with the exception of a small number of caps that tested bad which were re-stuffed. Build date is Feb. 42, who knows where and what this radio may have been involved in?

I’ve always wanted a functioning ARC-5 command set to accompany my BC-348-Q receiver. This article has inspired me.

Post readers: Anyone own a functioning ARC-5 (or any variants)? Please comment!

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Behind-the-scenes film of BBC Rampisham Down site circa 1961

Many thanks to SWLing Post contributor, Dave Porter, who shares a link to the following BBC Archive video of BBC RMP circa 1961. The BBC posted this video in light of the recent demolition of all but one of the original Rampisham Down towers.

Click here to watch the video on Facebook.

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1961 Film: “Tuning In Radio Sarawak”

Many thanks to SWLing Post contributor, Adid, who writes:

Hi Thomas, I just watched this very interesting DX film about RADIO SARAWAK.

It’s a behind the scenes look at radio in the tropics, with great vintage gear.

I don’t think it was FM as it’s was much expensive and coverage is limited. But on the other hand we don’t see the large MW antennas

What do you think?

Click here to view the film at the Imperial War Museum website.

Good question, Adid. The FM band wasn’t widely included on radios until the late 1950s and early 1960s. Since this film dates from 1961, I imagine some of those new transistor/valve radios could have included FM, although I imagine mediumwave was the choice band for regional broadcasts.

Hopefully, an SWLing Post reader can shed some more light on Radio Sarawak’s history! Please comment!

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EDXC conference featured on Andorra TV

The EDXC conference was held in Andorra this year and I wish I could have attended. When I lived in Europe, Andorra was one of those destinations always on my bucket list in no small part due to my affinity for Radio Andorra.

EDXC attendees–many are regulars here on the SWLing Post–were treated to a hands-on tour of RTVA and even featured in the news. Check out the following video:

Click here to watch the video at the RTVA website.

Hat tip to Kim Elliott for sharing this!

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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


Hardware used

SDR: RSP1a SDR from SDRplay?

Antenna: Modified GPS patch antenna for L-Band from SDR-Kits, model A154.?

Software used

SDRuno v1.32

VBcable (Donationware) vPack43

VAC (Paid for use) v4.60

JAERO (Free) v1.0.4.9

Tekmanoid STD-C Decoder (Paid for use) v1.5.1
Requires Java JRE, check your local laws before using this decoder.


(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.

Some regions that use the I-3 satellite services moved and migrated to the Inmarsat I-4 Satellites.  See the following document.

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

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).


(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

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.

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).

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.

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. 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. view page 17.

For more information about the RF GAIN settings of the RSP(x)

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


Click here to view on YouTube.

Click here to view on YouTube.

Click here to view on YouTube.

Click here to view on YouTube.


L-band frequency bank!jRFRiSaA!CcmRRRpjToxPzyGV9bf7MkDkKnqCYZCwwjC5curWj6g



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,

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!

Do you enjoy the SWLing Post?

Please consider supporting us via Patreon or our Coffee Fund!

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

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SDR Academy presentation videos

Many thanks to SWLing Post contributor, Alexander (DL4NO), who writes:

Parallel to the Hamradio fair in Friedrichshafen, Germany, there are talks and whole conferences. Over the last years, the “Software-Definded Radio Academy” (SDRA) was one of them.

You find the presentations on Youtube:

At least most of them are in English.

Thank you for the tip, Alexander! These videos are amazing! Wow–now I just need to find the time to watch them all.

I’ve embedded the videos and links below, for your convenience:

Markus Heller, DL8RDS: SDR-Academy @ HAM-Radio 2019 – A Summary


Dr. Carles Fernandez: An Open Source Global Navigation Satellite Systems Software-Defined Receiver

Mario Lorenz, DL5MLO: The AMSAT-DL/QARS Ground Stations for Qatar-Oscar 100

Mack McCormick, W4AX: FlexRadio: SDR Technology that Will Change How you Operate HF

Christoph Mayer, DL1CH: KiwiSDR as a new GNURadio Source

Manolis Surligas, SV9SFC: SDR Makerspace, Exploid SDR technology for space communications

Michael Hartje, DK5HH: Digital signal processing for the detection of noise disturbances

Prof Dr Joe Taylor, K1JT: Welcome Address and Questions & Answers

DL1FY, DC9OE, DG8MG, DL8GM: Charly25 SDR Transceiver

Alex Csete, OZ9AEC: SDR-Makerspace: Evaluation of SDR boards and toolchains

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