![.wxtoimg raspberry .wxtoimg raspberry](https://www.rtl-sdr.com/wp-content/uploads/2018/06/wxtoimg_screenshot.jpg)
Recorded satellite passes are decoded using free software – wxtoimg is a very popular application for this.
#.WXTOIMG RASPBERRY FULL#
Don’t run GQRX full screen, use a small window size to set GQRX running and then minimise during operation – not having to display the spectrum and waterfall has a big impact on RPi CPU loading.Lower FFT refresh rate to 10 frames per second or lower.Settings specifically to reduce the CPU load on the RPi: Filter bandwidth: about 38 kHz (GPredict will control the Doppler correction on the receiver so I don’t need to set this any wider than is necessary for the APT signal).Demodulation mode: NFM, max deviation = 25kHz (APT setting), Tau = Off.Dongle LNA gain setting: 44dB (set really high even with the additional LNA4All in the system, I’m sure there’s scope for reducing this but I haven’t tried yet).Dongle sample rate: 300000 (set fairly low in an attempt to narrow the bandwidth of the receiver and lower its susceptibility to pager interference on nearby frequencies).Settings I use for weather satellite reception on GQRX:
![.wxtoimg raspberry .wxtoimg raspberry](https://swradiorelay.com/wp-content/uploads/2021/02/NOAA1520210211-085145.MCIR-precip.png)
For ‘automatic’ use the receiving software is rtl_fm, see below for a description of that setup. This now runs on Raspberry Pi (2 and 3) although care needs to be taken with some of the settings to avoid working the RPi3 CPU too hard. GQRX receiver and GPredict tracking software running on the RPi Pixel desktop, acessed via VNC from my laptopįor ‘live’ use, the software component of the receiver is Alexandru Csete’s excellent GQRX SDR application. Wired networking is used to connect the RPi3 to my home network and I operate this system mostly via the VNC desktop shown below. The dongle receiver is now run from a Raspberry Pi 3 (I previously used a BeagleBone Black to make this dongle available on my home network and hosted the SDR software on an old spare laptop in the house, the same way I run my other network receivers). RTL SDR dongles again, specifically one from where they supply dongles with the 1PPM temperature-controlled oscillator to reduce the number of settings that have to be fiddled with (important for the use in schools). The LNA is placed almost immediately after the antenna (there is about 2.5m of RG58 cable between the antenna and LNA). It’s still a relatively low cost item at about £40 delivered to the UK but it’s the most expensive component in use here. My one extravagence in this setup is the inclusion of a Low Noise Amplifier (LNA), specifically an LNA4All. Nevertheless, the QFH antenna seems to do quite well. Over time this will be compared against the active V/UHF antenna I have installed my chimney. It’s a compromise and really just a first attempt to get something up and running. The antenna is mounted deliberately low on my garage to avoid exposing it to the full breadth of pager interference in the local area. I’ve added some extra horizontal struts to keep the helix shape better in the wind and also strengthened the main mast by inserting a steel clothes rail (a perfect fit into the plastic pipe) inside the lower section of the mast where the clamps are holding it to the wall bracket. The antenna I’ve built for this purpose is a Quadrifilar Helix (QFH) type based on G4ILO’s notes. OK, let’s go through it in a little more detail below… Antenna This allows me to easily sort through the (many) noisy images of low elevation or night-time passes and recognise the passes that have produced good images for further processing. A couple of Python scripts also run on the RPi3 to control automatic recording of the satellite passes and process the recorded files, opening them in Wxtoimg for decoding into basic images and then upload to a website for review. Basically a Raspberry Pi 3 (RPi3) is the star of the show running the satellite prediction software, software-defined radio and image decoding software. System overview WXSAT receiver setupĬlick on the system diagram above for an overview of the setup here. One of the aims of my setup is to see what can be achieved at low cost to support a school project detailed elsewhere on this site. There’s lots of tutorials out there on the web about the many methods there are of receiving these signals so I won’t replicate those here, this page is intended to outline my particular setup and show some of the results.
![.wxtoimg raspberry .wxtoimg raspberry](https://1.bp.blogspot.com/-95tLxlCN5LE/XSJn5zitVFI/AAAAAAAATXg/URhDDJWVnPYR0uYbwmuiOVfAMkSC_77AACLcBGAs/s1600/NOAA%2Bfig%2B3.png)
These are surprisingly easy to receive with basic equipment and provide really interesting imagery of the current weather overhead. I’ve been spending a lot of time over the last year playing with weather satellite reception, specifically the NOAA APT satellites, NOAA 15, 18 and 19, that broadcast their imagery in the 137 MHz band.