An antenna rotator can be used to automatically point a high gain directional antenna such as a Yagi at a low earth orbit satellite which passes overhead relatively quickly. Such as antenna can be easily connected to an SDR like the RTL-SDR to receive data such as HRPT weather satellite images from satellites.
Manuel's antenna tracker is inspired by the SatNOGs rotator, but he writes that his one was designed to slightly to be smaller and more powerful. For the driving motors he uses NEMA23 steppers which are mounted in a frame made out of 2020 aluminum extrusions. An Arduino Nano with optical end stops controls two TB6600 stepper drivers which control the motors. The rest of the parts such as brackets and gears are all 3D printed.
Attached to the antenna rotator is Manuel's home made carbon Yagi antenna. He also attempted to use his 1.2m dish but found that the rotator could not handle the weight.
The Radio Society of Great Britain (RSGB) and AMSAT-UK recently presented a number of talks at their latest convention held in October of this year. Some of the talks are SDR related and are interesting for those interested in satellite reception. A couple of interesting SDR related talks are presented below, and the rest of the talks can be accessed on their YouTube page.
Software defined radio for the satellite geek - Alex Csete OZ9AEC
In this talk Alex Csete (Oz9AEC) who is the programmer behind the popular GQRX software that is often used with RTL-SDRs discusses his latest work and some of his experiences with writing software for SDRs.
Going to space the libre way - Pierros Papadeas, Libre Space Foundation
In this talk Pierros Papadeas who is the founder of the Libre Space Foundation discusses their SatNOGS project. SatNOGS is a project that uses RTL-SDRs in custom 3D printed home made satellite tracking ground stations. It aims to enable easy access to live satellite data online by significantly increasing ground station coverage.
Thank you to Silvia P. for writing in and letting up know about the SatNOGs “No-Rotator” project, which looks a lot easier to build compared to their motorized rotator. SatNOGs is an idea and organisation that is trying to make it easier to set up a low cost networked RF ground stations for monitoring various satellites. The idea is to increase satellite ground station coverage all over the world and collect and share received satellite data over the internet so that anyone in the world can view and make use of up to date satellite data.
An original SatNOGs station is built as a motorized antenna rotator, with directional antennas that point and track satellites as they pass over the ground station location. The gears and most internal plastic parts are 3D printed, with the rest of the items like bearings, frames and motors being available on eBay. The problem is that building the rotator is quite a big project, and takes a lot of research, purchasing and building to get started.
Recently over on their Wiki a new type of non-rotator ground station has appeared. The no-rotator ground station still consists of the basic SatNOGs electronics including an RTL-SDR and Raspberry Pi. But instead of using high gain directional motorized antennas this ground station uses a much simpler turnstile antenna tuned to about 137 MHz. Unlike the rotator, the turnstile probably doesn’t have enough gain to pick up some of the weaker amateur satellites, but should be good enough for NOAA/Meteor weather satellites and ISS APRS etc.
Over on hackaday.io there is a project blog for the “Distributed Ground Station Network”. This is essentially an idea to build a large network of distributed RF receivers which automatically receive signals from sources like cube satellites and other beacons. The project mainly uses RTL-SDR dongles at the moment for their RF receivers. In some ways it appears to be similar to the SatNOGs project which won the hackaday prize two years ago but the DGSN appears to be more focused on “reverse GPS” which allows the detection and tracking of the location of small satellite signals through distributed receivers.
The Distributed Ground Station Network (DGSN) is a novel network concept of small ground-stations and connected via the internet for performing automatic scans for cubesats and other beacon signals. By correlating the received signal with the precise, GNSS synchronized reception times of at least 5 ground stations, it enables the positioning of the signal’s origin. Thus a global tracking of small satellites becomes possible in this “reverse GPS” mode. It allows mission operators to position and track their small satellites faster after piggy-back commissioning, when the final orbit is yet undefined and could differ from the specified orbit. Furthermore it allows permanent communication in “data-dump” mode. In this mode, DGSN ground-stations relay the received data to the servers and thus to the operator. Let’s track everything, together!
A satellite tracker is a motorized unit that points a directional antenna towards passing satellites. Most satellites are not in a fixed orbit, and will fly over your head a few times a day and will be receivable for a few minutes, and a directional antenna is usually recommended since the signals can be weak. The goal of the SatNOGS project is to set up various volunteer satellite tracker stations around the world, and network the received data on the internet, so that satellite data is always being received and shared.
Although the tracker works, he admits that there are some problems and that it is probably not as good as the SatNOGS recommended build, which is a more permanent solution. But the SatNOGS build requires access to a 3D printer and higher quality components, so Paul’s solution is a much cheaper solution to implement at least for experimentation.
The SatNOGS project aims to provide low cost satellite ground stations (where one critical component is currently an RTL-SDR dongle) along with free networking software in order to create a crowd sourced satellite coverage network. The SatNOGS project was also the grand prize winner of the 2014 Hackaday prize which saw them take away almost $200k US dollars of prize money.
Recently the SatNOGS team announced the release of their new satellite database which can be used to look up satellite transmitter information such as downlink frequencies. It is described as “an effort to create an hollistic, unified, global transmitter database for all satellite transmitters”. The database is open to everyone and requires contributions in order to grow.
In a previous post we talked about the SatNOGS project which aims to provide low cost satellite ground stations (where one critical component is currently an RTL-SDR dongle) along with free networking software in order to create a crowd sourced satellite coverage network. The SatNOGS project was also recently the grand prize winner of the Hackaday prize which saw them take almost $200k US dollars of prize money.
The SatNOGS hardware is a system that uses high gain antennas, tracking motors, a RTL-SDR and a PC running GNU Radio and other software to automatically track, receive and record satellites as they pass over head. The open source software works to automatically schedule observations and record them to an online database.