Tag Archives: Mode

PC-HFDL Display: Receive, decode and analyze the biggest net on HF!

HFDL is a net for data communications between airplanes and ground. The results can be shown on Google Earth . This screenshot shows a part of 29.000+ entries, received and processed on August 15th, 2016.

HFDL is a net for data communications between airplanes and ground. The results can be shown on Google Earth. This screenshot shows a part of 29.000+ entries, received and processed on August 15th, 2016.


Communications between air and ground is mostly done on VHF, UHF and SHF. But if an aircraft is out of reach of a ground station station due to the limited “radio horizon” of these bands, it has to maintain communications by either satellite or HF. This HFDL net is in fact the most massive professional user of HF right now. Within 24 hours, I get more than 40.000 live messages with a modest equipment.

With his software Display Launcher, Mike Simpson from Australia provides a most valuable tool to analyze up to nine channels in parallel. His software also draws positions and routes onto Google Earth. Mike has spent much energy on coping with many inconsistencies of transmitted data before it all really goes smoothly.

This free software is the vital part of a monitoring project to receive, demodulate and analyze live up to nine HFDL channels in parallel. Other ingredients you need is a software-defined radio (SDR), nine virtual audio cables (in fact, a piece of software) and a decoder software. Don’t forget an antenna and a PC …

This setup comprises a semi-professional monitoring station which will allow you to receive and track many of the nearly 3.000 airplanes using HFDL. This also covers the military, business jets, helicopters and some other delicate users. It maybe used as an important complement to Flightradar24’s web service, whenever their VHF/UHF/SHF-based net is out of range of the aircraft. This is particularly true over vast water masses like oceans and sparsely populated land masses. Furthermore, Flightradar24 erases some sensible flights from the raw material before publication on their website. This is clearly no “censorship”, but some thoughtfulness in regard to those countries where reception and publication of HFDL data is more tolerated than explicitly encouraged by the government.

In a 9-page PDF, I published a step-by-step recipe on how to set up such an HF monitoring station for up to nine parallel HFDL channel. You can download it here.

The best Digimodes: Test reveals surprising results


Digital communications with digimodes is a very efficient tool of HF communications. Hams are using RTTY for decades. Since the advent of PSK31 in late 1998, there have been developed a lot of digimodes with special applications in mind. Albeit, RTTY and PSK31 are still very popular.

When I asked myself: “What’s the best mode?”, I couldn’t get a reliable answer. And, really, it depends.

As a result, I made a setup for testing some chat modes on HF channels which are very much different from just flat noisy (AWGN) channels. The results were very much surprising: There are by far better alternatives to RTTY and PSK31 (see table above, reflecting some of the results).

This paper deals with setting up a real-world testbed and presents some results. Anyone is welcomed to replicate the test and/or extend it with other modes. Recent software of W1JHK has made the workflow much easier and faster since then.

Signals Analyzer: How to do it


With “Signals Analyzer”, the late Russian expert Sergey developed an excellent software to analyze digital signals. There still is no better software around to do this job at a budget price.

Signals Analyzer – Step by Step provides a short introduction in using this software with audio recordings.

It is a basic version of a German paper of 28 pages which you will find here. Thanks to its 65 and mostly self-explaining screenshots, it will make  an interesting reading also for people who don’t speak “The Awful German Language” (Mark Twain, 1880). Click here to download this enlarged Version.
Google Translate also offers a great help in reading it.

[Deutschsprachige Leser finden eine mit 28 Seiten und 65 Abbildungen ausführlichere Version dieser Einführung in die Analyse-Software “Signals Analyzer” hier.]

Here you find a link to the software and to additional information.

Antonio is one of the most avid users of this software and provides many examples on how to use it on this page.