Category Archives: Guest Posts

Guest Post: Decoding WEFAX using an RSP SDR and SDRuno

Many thanks to SWLing Post contributor, Mike Ladd with SDRplay, who shares the following guest post:

Basics to decoding WEFAX using an RSP and SDRuno

by Mike Ladd

SDR I use:
RSPduo from SDRplay using the Hi-Z input. Any model RSP’s can tune WEFAX transmissions. https://www.sdrplay.com/rspduo/

Antenna I use: Megaloop FX from Bonito. In an Inverted delta loop configuration pointed N/E-S/W. Any good antenna placed outdoors should be fine. It’s all about the SNR, not your S-meter reading. https://www.bonito.net/hamradio/en/mega-loop-fx/

Software:

SDRuno v1.32
SDRuno is an advanced Software Defined Radio application platform which is optimized for use with SDRplay’s range of Radio Spectrum Processing receivers.
https://www.sdrplay.com/downloads/

VBcable (donationware) vPack43
Transfers audio, digitally from one application (SDRuno) to another (Black Cat HF weather Fax) with zero loss.
https://www.vb-audio.com/Cable/

VAC (paid for use) v4.60
Transfers audio, digitally from one application (SDRuno) to another (Black Cat HF weather Fax) with zero loss.
https://vac.muzychenko.net/en/
https://www.sdrplay.com/docs/SDRuno_VAC.pdf

Black Cat HF Weather Fax (paid for use) beta 19
Decodes and produces images from the WEFAX transmissions from the output of SDRuno using a virtual audio cable.

Use the discount link available here
http://blackcatsystems.com/register/black_cat_hf_weather_fax_sdrplay_promo.html
https://www.blackcatsystems.com/software/hf_weather_fax.html

Black Cat Uno UDP
UnoUDP allows you control SDRuno’s VFO frequency from within Black Cat HF Weather Fax scheduler. This is done over a virtual com port pair using a virtual com port emulator. http://blackcatsystems.com/download/UnoUDP.zip

VSPE or COM0COM
VSPE is a paid for use app. COM0COM is completely free. Either one of these applications will work. A virtual com port emulator allows you to create a virtual com port. The pair will internally link Black Cat Weather Fax decoder to SDRuno’s using UnoUDP as the transport protocol.

VSPE http://www.eterlogic.com/Products.VSPE.html
https://www.sdrplay.com/docs/SDRuno_VSPE.pdf

COM0COM http://com0com.sourceforge.net/
https://youtu.be/dZg7puQ9Ajk

Introduction:

(some text taken and edited from various website)

This document is not a definitive guide to the WEFAX protocol, the process of decoding WEFAX images or reading a synoptic weather chart https://youtu.be/kzfNSvQREu8. This is only a collection of information that I have found scatter throughout the internet and re-compiled into a document, this document. Expect typographical mistakes, inaccuracies, or omissions.

WEFAX is an analog mode for transmitting monochrome images. It was the predecessor to slow-scan television (SSTV). Prior to the advent of the commercial telephone line “fax” machine, it was known, more traditionally, by the term “radio facsimile”.

Facsimile machines were used in the 1950s to transmit weather charts across the United States via land-lines first and then internationally via HF radio. Radio transmission of weather charts provides an enormous amount of flexibility to marine and aviation users for they now have the latest weather information and forecasts at their fingertips to use in the planning of voyages.

Radio fax relies on facsimile technology where printed information is scanned line by line and encoded into an electrical signal which can then be transmitted via physical line or radio waves to remote locations. Since the amount of information transmitted per unit time is directly proportional to the bandwidth available, then the speed at which a weather chart can be transmitted will vary depending on the quality of the media used for the transmission.

Radio fax data is available from the web on sites such as the ones hosted by the National Oceanic and Atmospheric Administration (NOAA). https://tgftp.nws.noaa.gov/fax/marine.shtml Radio fax transmissions are also broadcasted by NOAA from multiple sites in the country at regular daily schedules https://www.nws.noaa.gov/os/marine/rfax.pdf. Radio weather fax transmissions are particularly useful to shipping, where there are limited facilities for accessing the Internet.

Black Cat HF Weather Fax is a program that decodes WEFAX (Weatherfax, HF-FAX, Radiofax, and Weather Facsimile) transmissions sent from fixed locations around the globe.

A fax is transmitted line by line, typically at a rate of 120 lines per minute, or half a second per line. For example, to send a weather chart, you would start in the upper left corner. You would send the value of that pixel (dot), black, white, or perhaps a shade of gray. Then you would move over one pixel to the right, and send that pixel, and so on, until you reach the edge of the chart. Then you’d move all the way back to the left edge, and move down slightly, one line, and repeat the process.

Each pixel is converted into a certain audio frequency or tone. By convention, a tone of 1500 Hz represents black, 2300 Hz represents white, and frequencies in-between represent shades of gray. So if you listen to a fax transmission, you’ll hear the different tones as each pixel is present. For example, listen to a chart with mostly white background being sent. You’ll hear mostly the high pitch 2300 Hz, and some lower (1500 Hz) blips as each black pixel is sent. When a horizontal line is sent, you’ll hear a long half second burst of 1500 Hz, since the line is all black.

The transmitting station frequency modulates the carrier. That is, when a black pixel is transmitted, the carrier shifts down 400 Hz. When a white pixel is transmitted, the carrier shifts up 400 Hz. For a medium gray pixel, it stays on the assigned frequency. This is how most fax transmissions are made. Since we’re tuning it in SSB, it sounds to us as if the station is transmitting a variable frequency audio tone. The two processes are identical. This accounts for the confusion regarding what frequency to tune the radio to in order to properly decode the fax transmission. Different stations list their frequency in different ways. It is important to remember that a black pixel produces a 1500 Hz tone, and a white pixel produces a 2300 Hz tone within the AUX SP.

The setup works as follows. SDRuno demodulates the received signal. The demodulated audio is piped from SDRuno using virtual audio cable and sends it to the HF weather fax decoder. HF weather fax decoder receives this audio from the virtual audio cable that was demodulated from SDRuno and processes it, producing a picture on the screen

HF weather fax decoder can also set the VFO (tune) frequency of the RSP in SDRuno. This is done over the virtual com port pair using the UnoUDP application as the transport.

SDRuno can internally emulate a Kenwood TS-480, UnoUDP sends the Kenwood TS-480 serial commands via UDP over the virtual com port pair in order to set the frequency selected from the HF Weather Fax Scheduler option over to SDRuno.

You will need to install and configure the following applications.

1: A virtual audio cable.

2: A virtual com port emulator (If you would like HF Weather fax to communicate with SDRuno).

3: UnoUDP (If you would like HF Weather fax to communicate with SDRuno using the virtual serial emulator).

4: HF Weather Fax.

5: A simple wire antenna placed outdoors.

Virtual Audio Cable:

A virtual audio cable allows you to pipe the audio from one application (SDRuno) into another application (a decoder like HF Weather Fax) 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 install only one of the two that are available.

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

You can verify it the installation 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).

Virtual Serial Port:

A virtual com port emulator is only needed if you would like Black Cat HF Fax decoder the ability to tune the station in SDRuno when you double click a station name in the HF Fax Decoder scheduler.

Please use the links provided (additional PDF’s and YouTube videos) on Page 2 of this document for an installation / configuration walkthrough.

You can download my WEFAX frequency bank for use in SDRuno below should you choose not to use a virtual com port emulator. https://signalsacrossthepond.com/download/mike-kd2kog-sdrplay-complete/

Download Black Cat HF Weather Fax and UnoUDP:

Download the latest HF Weather Fax beta package and the UnoUDP application from the link provided on Page 2 of this document. I suggest making one main folder called HFfax and two subfolders within HFfax for each of the applications. One folder is for the HF Weather Fax Decoder and the other folder is for the UNO UDP transport application.

Double click the HF Weather Fax beta ZIP file you downloaded and extract the full contents of this ZIP into the folder you created on your local drive. Right click the “Black Cat Weather Fax” EXE file and send a shortcut to your Desktop.

Double click the UnoUDP zip file you downloaded and extract the full contents of this ZIP into the folder you created on your local drive. Right click the “UnoUDP” EXE file and send a shortcut to your Desktop.

You should have two shortcuts on your desktop, One for the decoder and one for the transport app.

Black Cat UnoUDP:

HF Weather Fax needs a way to communicate with SDRuno, this is done via UnoUDP and the virtual com port emulator.

Launch UnoUDP with the above configuration. Set your UDP Receive port to 58084 and your UDP send port to 58083. UnoUDP must be left running in the background, this will control SDRuno. You can minimize the application or right click the shortcut and have UnoUDP auto minizine on launch.

You should see a Firewall popup prompt asking permission to allow UnoUDP to pass data within the system. You must allow this traffic to pass or external control of SDRuno will not be possible from the HF Weather Fax decoder scheduler.

Assign 1 of the 2 com ports from the virtual com port emulator to UnoUDP (the 2nd com port will be assigned to SDRuno). My com port pair is Com 1 and Com 2, SDRuno uses Com1 and UnoUDP uses Com 2.

Black Cat HF Weather Fax:

HF Weather Fax needs to be configured in order to communicate with UnoUDP, this is done via the UDP settings. Click “Edit” and “Preferences” Set the UDP Send port to 58084 and the UDP Receive port to 58083.

You should see a Firewall popup prompt asking permission for HF Weather Fax to pass data within your system. You must allow UDP traffic to pass or external control of SDRuno will not be possible from the HF Weather Fax decoder scheduler.

SDRuno:

SDRuno needs its Output assigned to the Virtual Audio Cable. The output can be changed via the RX CONTROL panel, clicking the SETT. button on the top left and clicking the OUT tab.

SDRuno needs a com port assigned so it can be externally controlled. The serial port is assigned via the RX CONTROL panel, clicking the SETT. button on the top left and clicking the CAT tab.

I recommend running the RSP in LOW-IF mode, this is selected via the MAIN panel. This reduces the need to track separation between the Tuned frequency and LO (local oscillator) https://youtu.be/Fsns4P3JxrM

LOW-IF mode also minizines the LO being placed outside of the desired preselect filter of the device in use, Remember the preselect filter is automatically enabled based on the LO frequency https://youtu.be/w-vkiVp7Q4E

I also recommend leaving the IF AGC enabled and placing the RF GAIN as high as possible without causing an ADC OVERLOAD warning within the MAIN panel. If an ADC OVERLOAD warning appears, back the RF GAIN down.

https://www.sdrplay.com/wp-content/uploads/2018/06/Gain_and_AGC_in_SDRuno.pdf

Your first WEFAX decode (Using UnoUDP)

Launch UnoUDP and minimize it.

Launch Black Cat HF Weather FAX.

Launch SDRuno. Set the mode to USB and the filter width to 2.8k
HF weather fax will not set the mode or filter width at this time.

Click the Sked button in Black Systems HF Weather Fax. A current WEFAX transmission schedule will appear. Stations listed in White are either scheduled to transmit or about to transmit based on your computers clock. Stations show in Grey at the bottom of the list are currently off the air or not transmitting.

In the Freq Offset: box enter -1.9 and hit enter (Reason for this is on Page 5).

Click any of the stations listed in the Fax Transmission Schedule and it will automatically tune SDRuno to the correct frequency.

Black Cat HF Weather Fax folder will have a file named “Black Cat HF Weather Fax Docs” Please view this file to understand some of the advanced features available.

Your first decode (Without UnoUDP)

Launch Black Cat HF Weather FAX.

Launch SDRuno.

Navigate to the Memory Panel (MAIN panel and click the MEM PAN button)

Right click the Memory panel and select “Open bank”. Navigate you C drive telling SDRuno the location of WEFAX.s1b

Double click any of the frequencies shown within the WEFAX bank and SDRuno will set the correct mode and tune that station. My WEFAX.s1b file defaults to the Hi-Z port. If your device lacks a HI-Z input, navigate to the port section within the memory panel, double click the stations port you want to edit and change it to the correct port that’s available or in use for your device. Right click the memory panel and “Save bank” to save the changes.

To use my SDRuno WEFAX frequency bank properly. The MCTR button must be enabled within the RX CONTROL panel, enabling this option allows you to double click and tune a station that is stored within the WEFAX bank. Make sure the LO is not locked in the MAIN panel (LO LOCK).

If a decoded WEFAX image looks blocky or skewed or possibly pixeled, I recommend that the lock output fractional resampler option is enabled in SDRuno. You can enable this from the RX CONTROL panel, clicking the SETT. button on the top left and clicking the OUT tab.

I hope this document helped guide you in getting started with decoding WEFAX transmissions from around the world. I am sure I missed some key features, remember this is only a primer/basics to decoding WEFAX. I do have an accompanying video located here

https://youtu.be/vAYGVimzNX8

Warmest of 73,
Mike-KD2KOG

Disclaimers

SDRPlay modules use a Mirics chipset and software. The information supplied hereunder is provided to you by SDRPlay under license from Mirics. Mirics hereby grants you a perpetual, worldwide, royalty free license to use the information herein for the purpose of designing software that utilizes SDRPlay modules, under the following conditions:

There are no express or implied copyright licenses granted hereunder to design or fabricate any integrated circuits or integrated circuits based on the information in this document. Mirics reserves the right to make changes without further notice to any of its products. Mirics makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does Mirics assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation consequential or incidental damages. Typical parameters that may be provided in Mirics data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. All operating parameters must be validated for each customer application by the buyer’s technical experts. SDRPlay and Mirics products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applications intended to support or sustain life, or for any other application in which the failure of the Mirics product could create a situation where personal injury or death may occur. Should Buyer purchase or use SDRPlay or Mirics products for any such unintended or unauthorized application, Buyer shall indemnify and hold both SDRPlay and Mirics and their officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that either SDRPlay or Mirics were negligent regarding the design or manufacture of the part. Mirics FlexiRFTM, Mirics FlexiTVTM and MiricsTM are trademarks of Mirics .

SDRPlay is the trading name of SDRPlay Limited a company registered in England # 09035244.

Mirics is the trading name of Mirics Limited a company registered in England # 05046393

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Mike’s tips for decoding SW Radiogram broadcasts

Paul’s report from the UK’s National Hamfest

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Many thanks to SWLing Post contributor, Paul W4/VP9KF, who shares the following report from the UK’s National Hamfest:

Your travelling foreign correspondent took in a visit to the UK’s National Hamfest held in Newark, Notts.

We arrived right on opening time (10am) and were the first in the door.

There was a ‘rush’ to the SDRPlay stand because they were giving away some nice FLASH drives to the first 25 people to get there. The author managed to get one and later found it was a) fast b) pre-loaded with software for all things SDRPlay. They were busy showing the new diversity software amongst other things.

bhi had some new hardware and I took the chance to thank them for a prize won in the W5KUB Xenia draws.

The hall was pretty empty (this was the second day and a Saturday). Noticeable was that some products were already sold out and on back order [such as the amazing nanoVNA].

It’s a shadow of the former Leicester Show which was the precursor to this event with a lot less parts on sale.

I had a long chat with Eric of Elecraft while twiddling with the K4 and suggested some improvements to the button usage, which he said would be tested in use. A date of the ‘beginning of the year’ for first shipments was mentioned and that the first batch would be ‘large’ [much more than 100] followed by smaller batches. Components are on order, some of which are on long lead times (and have to arrive in good shape for surface mount assembly down the line).

The K4 was ‘playing’ the 7 Area QSO Party on several bands and most controls were operable. This was streaming from an IQ recording and an RF modulator straight into the rig. Just exactly how close this was ‘to the original sound’ and TRUE performance of the rig and/or software is
to be seen.

The weather was fine for the show (although patchy – XYLs reported that it poured with rain back in Nottingham itself!). Turnout was very disappointing and a lot of grey hair was to be seen in the one (yes one) Hall Building.

73,

Paul W4/VP9KF [and G4BKI]

Thank you so much for the report, Paul. I do want to make a pilgrimage to the UK’s National Hamfest one year–any excuse to visit my home-away-from-home country!

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Guest Post: Paolo’s Tips For Avoiding Internet Scams

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Many thanks to SWLing Post contributor, Paolo Viappiani (SWL I1-11437), who shares the following guest post:

Some Tips For Avoiding Internet Scams

by Paolo Viappiani – SWL I1-11437

[email protected]

Recently, I have been amazed by the growing number of frauds that foul up the radio market on the Internet (I was scammed too), so I decided to write a post in order to help anyone who is interested in buying anything on the web.

First, it’s worth saying that most scam attempts involve high-quality items that are offered at surprisingly low prices. One of the most significant examples involves some rare (and discontinued) high-end radios by National Panasonic, typically the RF-8000 and RF-9000 models. In this post, I make an example of the RF-8000, but scams also concern radios of other brands..

Generally speaking, a number of advertisements on the most known advertising/classifieds sites (Quoka.de and ebay-kleinanzeigen.de in Germany, Subito.it, Kijiji and AAAnnunci.it in Italy, Le Bon Coin in France, ComoFicho in Spain, etc.) are mirrors for larks only, and we have to pay a great attention in order not to be scammed.

But… how can we recognize a scam?

The most common scams use the following techniques:

The scammer advertises a very rare radio in like-new condition at an unbelievably low price. The buyer does not want to miss the bargain, so he contacts the seller and promptly transfers the money to him without further ado, but after that he waits in vain for the delivery of his item.
High quality radios offered very cheap. If you contact the seller, the item is suddenly abroad. The alleged seller then proposes to handle the purchase through a “trust company”. The radio should be paid for in advance and the amount sent via cash transfer, but after that you never hear anything from the seller again.
Alternatively, the buyer is requested to to deposit the money to the eBay company account to get the product. But the account is fake (really eBay has no “COMPANY ACCOUNT” and never handles private transactions–!), so the buyer loses his money and receives nothing in return.

Please also notice that often the fraudulent sellers offer a free period for evaluating the item, saying that if you do not like the device, you can send it back. Please don’t fall into this trap, it is only one of the means the scammers use to entice you to purchase, but it is not true at all!

In the following section I’ll recount some examples of real scams concerning the National Panasonic RF-8000 and RF-9000 radios (but, as I already mentioned, the scams involve many other radios and also high-quality electronic or electro-acoustic devices).

One of the most prevalent (and very dangerous) scams concerning the RF-8000 radio is (was) perpetrated by a Portuguese seller who offered (for about 2.300 Euro on the AAAnnunci.it and Quoka.de websites) a very nice appearing radio, look at the photos below.

Really a radio in like-new conditions, uh?

But it is just a trap: most of the Panasonic RF-8000 radios have the leather covers on all sides cracked like crocodile skin (look at the image below); only a very few units still have the covers in pristine condition and for sure they cannot be found at cheap prices!

Incidentally, all the pictures used by that scammer (including the two shown in the first two pictures above) were stolen from an old eBay advertisement of October 2018 and that wonderful appearing RF-8000 was sold to a radio collector in China for about $ 5,000 USD.

But the same images also recently appeared on some European advertisement websites (in Italy and in Germany too); if you ask for info, you’ll be contacted soon by a seller from Portugal who offers to handle the purchase through a “trust company” of his confidence, named TrafCargo (beware of this, it is a convincing but fake website!).

Then, the seller requests that the amount for the radio and its shipping costs be sent via a bank wire transfer to the fake transportation company.

After that you never hear anything from the seller again.

Very similar scams are also found in various advertisement/classified websites (Quoka.de, ComoFicho.com etc.), look at the images below as examples. If such items are offered cheap, it is for sure a scam:

A similar attempt of fraud is commonly perpetrated by other people, including a female seller from Spain. As you might suspect, she offers something that looks like a real bargain, but it’s only a scam. After you have asked for info on the product, you receive a message in which it is specified that the item is located abroad and you are asked to deposit money to a fake “eBay” account (note that eBay does not accept any payment outside their site!).

In order to be more persuasive, often the scammer attaches a copy of his/her passport of other identity documentation in order to appear as a serious seller–please do not trust them however!

Also, beware of the fake “eBay invoice” that sometimes the scammers send, and for anything that involves eBay, contact the eBay helpdesk, ask for specific info and report them the fraud eventually.

In the following section you’ll find some useful advice on recognizing scams and making secure and safe purchases on the Internet:

Always beware whenever the item is in a place (or a country) different from the one that was specified in the advertisement; also there is a valid reason for suspicion when the name or the address of the advertiser does not match the seller’s ones;
Do not completely trust the pictures sent by the seller (they could be stolen from the Internet) and don’t forget to proceed to a “Google Image” search in order to find the sources of similar ones;
Always ask the seller for some specific pictures or videos (radio precisely tuned on various frequencies and/or modes) and do not accept any runarounds about it (“you can try the radio for some days”, etc.); normally the scammers do not have the items they offer at hand, so they are not able to satisfy your precise requests.
Never pay for the item in advance by rechargeable cards like Western Union or other non-secure ways of payment. Also the Bank Transfer (Wire Transfer) is not a secure form of payment in order to avoid frauds;
Always ask the seller for payment by PayPal “Goods and Services” (NOT “Send money to friends”). If you choose Goods and Services, your purchase will be fully covered by the PayPal warranty.

And, in the case that you are a victim of a scam anyway, please always report the incident to the Police or the Judiciary of your Country, and don’t forget to also warn the site where the announcement was found.

Following the above advice should be sufficient to avoid any scam. So, good luck on your future web purchases!

This is excellent advice, Paolo. Thank you for sharing your experience!

One of my favorite bits of advice above–and one I use anytime I make a significant purchase via a classifieds website–is to ask the seller for specific photos or a video of the item. As you say, they don’t typically have the item on hand, so can’t comply and will make up excuses. That’s a major red flag!

Another red flag? If it sounds too good to be true, it probably is! Trust your instincts and avoid the hassle and headache.

Post readers: Please share any other advice you have about avoiding radio scams. Have you ever been the victim of a scam? How did it play out? Please comment!

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Jack’s Tailgate DXpedition

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Many thanks to SWLing Post contributor, Jack Blanke (WB5LVP), who shares the following:

Really enjoyed your article yesterday, and felt compelled to respond with a similar DX’ing jaunt of mine two days ago.

I found myself in the same mindset and ventured out to a nearby peaceful fishing and yacht harbor to try out my new Tecsun PL-380. I have had it about 10 days and I have figured out that I have about all the urban power line and electrical noise I can stand at my home location, so I was headed out to give the 380 a chance to exercise its ears.

I found the most deserted corner of the parking lot at the harbor, positioned my pick-up for maximum shade, dropped the tail gate to provide a work surface, strung out about 75 feet of stranded #14 insulated copper wire and positioned my portable chair for DX action.

I did not have a copy of the WRTH, but I do use an iPhone app called Shortwave Broadcast Schedules by Black Cat that has really worked well for me and I highly recommend. With great anticipation, I flipped the power switch and enjoyed the most beautiful silence from man made electrical noise that I have ever experienced!! I could not believe how much quieter the receiver was in a more more pristine environment.

Jack’s ultralight Tailgate DXpedition kit

I opened the app to search for some DX’ing frequency possibilities, began tuning the bands and I was amazed at the number of short wave broadcast stations, the strength of their signals and the pure listening quality coming out of my 380, which is little larger than a pack of cigarettes!! I have been a licensed ham since 1970 and at one point back in the early 1970’s, I had a complete R. L. Drake HF station which might be called “Boat Anchors” by today’s standards. I was now listening to stations from around the globe on a receiver that comfortably fit in my pocket and a long wire strung out to a nearby “NO PARKING” sign post.

The Tecsun PL-380

Within a matter of a couple of relaxing hours, I had logged and enjoyed listening to Radio Habana, Voice of Vietnam, China Radio Int., Voice of Nigeria, Radio Romania Int., KBS World Radio and several other stateside shortwave broadcasts from Miami, Nashville & Lebanon Tennessee. I was totally thrilled at the performance of the radio/antenna combo and I anxiously await the opportunity to visit the area again for another Tailgate DXpedition!! I am particularly looking forward to fall days and cooler temps to go lose myself in the reverie of the shortwave bands, this time with a few brewskies in the ice chest, along with lunch.

It was a thoroughly enjoyable day and I could not help but relate to your article when I read it!! Next time, I plan to photograph my Tailgate DXpedition, simple though it may be to share with others. I have been away from radio for some time, but have maintained my amateur license for nearly 50 years. Now that I am retired and have more time, I plan to enjoy my long lost love of radio once again.

Thanks for your web sight. I look forward to the newsletters and enjoy its resources.

Take care.

’73’s

Jack Blanke

Thanks so much for sharing your story, Jack!

Isn’t it amazing how the shortwave bands simply open up when you remove all of the urban noise that plagues our receivers? That’s the brilliance behind impromptu DXpeditions. Plus, I’ve always believed that radio is best enjoyed outdoors.

We look forward to seeing some photos and a report of your next Tailgate DXpedition, Jack!

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Please consider supporting us via Patreon or our Coffee Fund!

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

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

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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.

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.

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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Guest Post: Summer Daytime DXing 2019

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Many thanks to SWLing Post contributor, TomL, who shares the following guest post:

Summer Daytime DXing 2019

by TomL

I took note of the mediocre band conditions this summer amongst amateur radio operators as they were making off the cuff comments about still being in a solar minimum. Some had gone out and bought upgraded transmitters to solve the problem (MOAR WATTS!). And more power thrown at a weak ionosphere does seem to help get a signal farther. I had not been out since the spring and decided to find out for myself. But instead of more watts, I wanted more height.

Greene Valley Scenic Overlook is open to the public from May through October on weekends only (and only from 11am-6pm). It was the largest land fill (aka, garbage dump) in Illinois, now covered over and producing captured methane gas. On August 3 & 4, I ventured over there to see if its 190 feet above the surroundings might help my radio reception.

After trying my luck with a 12 foot vertical antenna on a tripod (and numerous children running around it chasing butterflies or looking at the view of Chicago), I went out the next day and parked away from anyone and put up my 19 foot vertical on the roof of the car. This setup is still amazing to me and works much better than the tripod mounted antenna, probably because it has a proper ground plane as well as being 7 foot taller.

So, yes, the conditions were so-so, not too bad and not too good. Lots of weak signals and some empty frequencies that I had expected to hear some South American stations around the 5 – 10 kw range. Weak stations from Asia were more scratchy sounding than usual even with the extra 190 feet of height. Here are 5 broadcast recordings as a sample (times in UTC):

9920 kHz at 21.14 – Radio Thailand in Thai, just catching the end of the broadcast:

9685 kHz at 21.20 – Radio Free Asia in Chinese from Kuwait:

9650 kHz at 21.23 – Radio Guinea in French:

9445 kHz at 21.30 – All India Radio in English (fighting off computer generated noise on my SDR and cheap Dell laptop) and just getting a station identification:

11780 kHz at 21.44 – Radio Nacional de Amazonia booming in with the usual annoying host yelling enthusiastically over every tune he played:

Running out of things to listen to, I wandered over to the 20 meter amateur radio band and found a different situation. Propagation was decent between the Western hemisphere and Europe. Lots of “pile ups” going on with people trying to make contact with their trans-Atlantic counterparts. Some said they were running 500 watts or more, so more power does seem to help! Here are 5 recordings to show how active it was:

14171 kHz at 21.55 – Inaki (F5RAG) from southwestern France conversing with Carlos (YV3CRT) in Venezuela (surprised anyone is left in Venezuela with operating radio equipment and not sold off for food with the ongoing difficulties there). Then Inaki makes contact with Alejandro (CE2ATS) from Chile with a good signal. All in Spanish:

14199.38 kHz at 22.04 – Ervin (VE3GAL) tries his QRP portable setup from Ontario to contact Ron (F4VSM) in Southwestern France who has a 500 watt setup and large Yagi antenna. Sometimes things do not go so well but that is the challenge of using low power, maybe around 10 watts (meaning that just because you can hear them, you cannot always transmit to them with the same effectiveness and vice-versa, for various reasons):

14228 kHz at 22.12 – “BAN” (IZ1PNT) from Italy makes contact with Norman (N3PVQ) in FL after asking everyone to be quiet. Good control over the frequency:

14238 kHz at 22.17 – Slavko (S57DX) booming in, making a contact (Rob, KK4HEQ) in Florida:

14245 kHz at 22.24 – Gabrielle from the Czech Republic, participating at a Youth event using station OL88YL contacting Ira (VP2EIH) in the British Virgin Islands and then another dude from Florida, Roy (AD4AN). She handled it very well:

This outing was quite educational and I find it curious that people running 1000 watts or less are able to be heard well between continents but the large broadcasters were difficult to hear. Antennas pointed in the right direction, at the right time of day and frequency, can certainly do amazing things, plucking those weak signals out of the air so easily. And I do think the extra height had something to do with hearing this magic, too!

Happy Listening,

TomL

NOTES:

An easy way to lookup amateur radio operator “call signs” is to go to web site QRZCQ.com which does not need a login. Some records may be out of date, but most of it is accurate.
Setup used was a cheap Dell laptop, Windows 10, SDR Console 3.03, connected to the AirSpy HF+, a Palstar amplified preselector, and an old Kiwa BCB filter, then going up to the car roof magnetic balun (a Palomar MLB2) which is then connected to the 4 magnet base and the MFJ 19 foot stainless steel antenna. You can read about it here:

https://swling.com/blog/2018/07/guest-post-backpack-shack-3-0-part-3/

Brilliant report, Tom! It’s true: the bands are fickle, but like you I always find interesting things to hear on HF. I think your setup using your vehicle as the ground plane for the antenna is a fantastic idea. Plus, set up is easy, self-supporting, and you’ll never have to worry about a park ranger, for example, complaining because you have a wire suspended from a tree. And when there are no trees? You’re still golden.

Thanks for sharing your experience and DX! Amazing that even with mediocre conditions, you still snagged some distant signals.

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Category Archives: Guest Posts

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Introduction:

Virtual Audio Cable:

Virtual Serial Port:

Download Black Cat HF Weather Fax and UnoUDP:

Black Cat UnoUDP:

Black Cat HF Weather Fax:

SDRuno:

Your first WEFAX decode (Using UnoUDP)

Your first decode (Without UnoUDP)

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Mike’s tips for decoding SW Radiogram broadcasts

Paul’s report from the UK’s National Hamfest

Guest Post: Paolo’s Tips For Avoiding Internet Scams

Some Tips For Avoiding Internet Scams

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Jack’s Tailgate DXpedition

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

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

Hardware used

Software used

Introduction

Software installation

JAERO

Tekmanoid STD-C Decoder

Putting all the pieces together

Additional resources

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Guest Post: Summer Daytime DXing 2019

Summer Daytime DXing 2019

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