Tonight I tested the turnstile antenna and Airspy on the Meteor-M N2 LRPT downlink signal. It was a good, high elevation pass and it looks like the signal is strong enough to decode the transmitted images.
Some time ago I got a 137 MHz turnstile antenna from Jørn OZ6TA. We decided to build an automated NOAA weather satellite image receiver using a modern SDR device. He also had an Airspy he wasn’t using and so it became the SDR radio we were going to use for this.
Today we have a guest post by Kirill Snezhko (@argrento) who describes how to get Gpredict working on Android tablets. Note that this is not about a native Android port of Gpredict, but how to get Linux installed as an Android app and run Linux applications like Gpredict.
About a year ago I posted a step-by-step guide about how to receive NOAA APT weather satellite images using Gqrx SDR and the Funcube Dongle. Today, I tried to repeat the procedure using my ezcap eztv666 rtlsdr dongle with very good results.
I have previously written about interference from FM stations on the HO-68 linear transponder. Now it appears the other satellites with linear transponders also suffer from local FM traffic by people who haven’t got a clue that they are transmitting in the satellite uplink segment of the 2 meter band.
Here is a new recording showing an updated Gqrx receiving the FO-29 amateur radio satellite using the Funcube Dongle. Previous recordings used an early version of Gqrx. It was a very quiet pass, most notable thing was probably the Russian and Spanish hams using FM. They probably don’t have a clue that their signal comes over a satellite transponder. Another video recording focusing on the FM transmissions during this FO-29 pass is available here.
Thanks to Jan Simon, DL2ZXA, we now have daily builds of Gpredict for Ubuntu 10.04 – 12.04, both 32 and 64 bit. Jan’s recipe fetches the code imported from SourceForge, merges it with the translations done in the Launchpad, then builds the packages and puts them in the Gpredict teams Daily builds PPA. You can use this PPA as you would use any other PPA; if you don’t know how check out the instructions on the PPA page. Obviously, this is only recommended for testing and not for production use.
One of the great advantages of software defined radio receivers is that tuning receiver settings is a matter of adjusting software parameters. Gqrx is no different here and has optimal settings built in for weather satellite reception. This tutorial describes how to receive automatic picture transmissions (APT) from NOAA weather satellites using Gqrx SDR, record them to a WAV file, and finally decode the images using the free and open source Atpdec decoder. If you follow this guide you can end up with very nice results such as the one shown at the end.
With both the frequency controller and FFT plot widgets in place gqrx was ready for the first on the air tests. The video below shows the first reception of the AO-27 amateur radio satellite during orbit 92436 and 92437, using the Funcube Dongle receiver that I use for portable space communication.
I have wanted to implement a simple APT decoder for the NOAA weather satellites in GNU Radio for quite some time now, in particular since the USRP equipped with a TVRX or WBX daughterboard and a GNU Radio FM receiver can be an extremely good receiver for this purpose. Today I have spent some time looking at the details of decoding APT and actually ended up with a working prototype implemented using the GNU Radio Companion.