Tagged: navtex

TechMinds: Building an Automated NavTex Receiver using a Raspberry Pi and SDRplay

Over on the TechMinds YouTube channel, Matt has uploaded a video tutorial showing how to create an automated NavTex receiver using a Raspberry Pi and an SDRplay software- defined radio.

NavTex is a safety and navigational information radio text broadcast system for mariners, typically broadcast at 518 kHz and 490 kHz. On ships, it is typically received by dedicated hardware that prints out information on a piece of paper as it comes in. However, with an appropriate antenna and an SDR, it is possible to receive and decode NavTex signals at home. 

In his video, Matt shows how a Raspberry Pi loaded with a piece of software created by "boat-comm" can be combined with an SDRplay RSPdx to create a homemade automated NavTex receiver. Matt shows how to install the software and goes on to demonstrate it in action.

Currently, only SDRplay receivers are supported by boat-comms software, but it's possible that in the future, other SDRs may be supported, too.

Automated NavTex Receiver Using A Raspberry Pi & SDRPlay SDR

If you're interested, boat-comm also has a video about his software available on his YouTube channel and we've embedded his video below.

NAVTEX on raspberrypi for sailors

A Homemade Boat Computer with RTL-SDR for Weather Fax, NavTex and more

Over on Hackaday we've seen a post about [mgrouch]'s "boat computer" which consists of a Raspberry Pi 4, HDMI display, and a whole slew of sensors and receivers useful for a marine environment including an RTL-SDR.

The built in equipment includes a GNSS receiver, orientation sensors, AIS receiver, 4G and WiFi, lightning EMI sensor and alarm, optional autopilot integration, rudder angle sensor, connections to boat instruments like wind, depth, speed, temperature, barometric and humidity sensors, an Iridium receiver, and finally an RTL-SDR for receiving weather fax, NavTex, satellite weather, AIS, RTL 433, morse code and more. It really is an "all-in-one" device.

His blog post explains in detail how each of the components work in the system, and in particular for the RTL-SDR he shows how you can use the boat computer to receive FM via GQRX, and NavTex via the Java based Frisnit Navtex decoder. Navtex is a marine radio service that transmits at 518 kHz or 490 kHz. It provides text data regarding weather forecasts, weather warnings, navigational information, and urgent maritime safety messages. For his antenna he writes that he uses a 10 kHz - 30 MHz Mini Whip antenna that he purchased on Aliexpress.

mgrouch's Boat Computer with RTL-SDR
mgrouch's Boat Computer with RTL-SDR

Decoding NavTex with an SDRplay RSPDx, SDRUno and YanD

Over on YouTube TechMinds has uploaded a new video explaining NavTex and showing how to decode it with an HF capable SDR like the SDRplay RSPDx. NavTex is a marine digital data radio service designed for transmitting information like navigational and meteorological warnings, weather forecasts and maritime safety information. It is broadcast in either the MW frequency band at 490 kHz and 518 kHz or in the HF band at 4209.5 kHz.

In the video TechMinds uses a guide put out by Mike Ladd from SDRplay (pdf warning). The guide explains how to connect SDRuno to a NavTex decoder called YanD via a virtual audio cable. The rest of the video shows a NavTex message being decoded, some sample messages, and a closer look at YanD. 

Even if you don't use an SDRplay, the guide could be adapted for other SDRs too.

Decoding NavTex with Software Defined Radio - SDRuno RSPdx