Category: Satellite

Simulating GPS with LimeSDR and Receiving it with an RTL-SDR

In previous posts we showed how Phillip Hahn had been trying to use his RTL-SDR as a GPS receiver on a high powered rocket in order to overcome the COCOM limits which prevent commercial GPS devices from operating when moving faster than 1,900 kmph/1,200 mph and/or higher than 18,000 m/59,000 ft.

In order to test future flights with the RTL-SDR GPS receiver, Phillip has been simulating GPS rocket trajectory signals and using his LimeSDR. The RTL-SDR then receives the simulated GPS signals which are then fed into SoftGNSS for decoding. The simulation simulates the Japanese SS-520-4 rocket which is a 32′ long, 2′ diameter small high powered rocket capable of putting loads like cubesats into orbit affordably. Using the simulated data Phillip is able to calculate the trajectory and see all the motor burns in the velocity profile.

While Phillip intends to use the RTL-SDR on a similar rocket in the future, he notes that the simulation does not take into account problems such as thermal noise, or RF interference, rocket jerk, satellite occlusion and vibration problems.

LimeSDR Simulated GPS Rocket Trajectory Received with RTL-SDR.
LimeSDR Simulated GPS Rocket Trajectory Received with RTL-SDR.

30% Off Outernet L-Band RTL-SDR DIY Kits – $70 for RTL-SDR, LNA, Antenna, CHIP and Battery

Outernet is an L-band satellite service that aims to be a “library in the sky”. They are constantly transmitting data such as up to date news, weather updates, Wikipedia pages, books, ISS APRS repeats and much more. Their DIY receiver kit consists of a lithium battery pack, L-band patch satellite antenna, LNA with built in filter, C.H.I.P mini Linux computer and an RTL-SDR E4000 or V3.

The DIY kit is normally priced at $99 USD, but right now they are running a 30% off Christmas promotion, bringing the price down to $69.30 USD. If you don’t need the battery pack, the sale price is then only $55.30 USD. This seems like a very good deal as normally just the patch antenna and Outernet LNA would be almost $50 USD in total.

To get the discount you must purchase directly from their store and use the coupon 30OFF. The promotion ends 31 December 2016 at 11:59 PM CST so get in quick.

The Outernet items you get for $70 USD.
The Outernet items you get for $70 USD.

A Cooking Pot L-Band Antenna

Over on YouTube Adam 9A4QV has uploaded a video showing us his home made cooking pot L-band antenna. The antenna consists of a large aluminum cooking pot which acts as a reflector and a cross-dipole inside the pot acting as the antenna.

The antenna is placed at a height of exactly 1/4 wavelength from the base of the pot, and the cross dipole wire lengths are 0.52 and 0.42 wavelengths long. They are different wavelengths as this achieves circular polarization. Adam writes that the gain should be about 4 – 5 dB’s better than a patch antenna.

The first video shows the performance of the antenna in SDR# when receiving the Outernet and Inmarsat/Alphasat L-band satellite signals indoors. Together with an LNA4ALL and RTL-SDR, Adam gets about 8 dB on the Outernet signal and 24 dB on AERO.

Cooking pot L band antenna

L band cooking pot antenna

SSTV From the ISS Scheduled for Dec 8 – 9

The International Space Station periodically schedules radio events where they transmit Slow Scan Television (SSTV) images down to earth for listeners to receive and collect. This time they have scheduled SSTV images for Dec 8 1235 – 1800 UTC, and December 9 1240-1740 UTC. The ARRL announcement reads:

Slow-scan television (SSTV) transmissions from the International Space Station (ISS) are scheduled for December 8-9. The SSTV images will be transmitted from RS0ISS on 145.800 MHz FM as part of the Moscow Aviation Institute MAI-75 Experiment, using the Kenwood TM-D710 transceiver in the ISS Service Module.

MAI-75 activities have been scheduled on December 8, 1235-1800 UTC, and December 9, 1240-1740 UTC. These times correspond to passes over Moscow, Russia. ISS transmissions on 145.800 MHz FM use 5-kHz deviation, and SSTV transmissions have used the PD120 and PD180 formats.

The ISS Fan Club website can show when the space station is within range of your station. On Windows PCs the free application MMSSTV can decode the signal. On Apple iOS devices, use the SSTV app.

These SSTV broadcasts can usually be easily heard with an RTL-SDR and appropriate satellite antenna such as a QFH, Turnstile or a hand held Yagi. Many listeners have reported in the past as being able to receive them even with non-satellite antennas such as discones, ground plane, rubber duck and long wire antennas, so try your luck even if you don’t have the right antenna.

We recommend using the Orbitron software to track the ISS, but you can also use the web tracker on issfanclub.com as recommended by the ARRL.

An SSTV image from the ISS sent last April
An SSTV image from the ISS sent last April from http://www.issfanclub.com/node/40913

 

Radio For Everyone: An Easy Homemade Outernet Antenna, More FlightAware Pro Stick Plus Results

Akos from the radio for everyone blog (formerly known as the rtlsdr4everyone blog) has uploaded two new posts. On the first post he shows some further tests on the new FlightAware Prostick plus. The Prostick is an RTL-SDR that contains a built in LNA and the Prostick plus adds an additional SAW filter on the stick. For him the Prostick Plus works significantly better than the regular Protstick + external FA cavity filter and also gets about twice the ADS-B reception reports as our V3 which does not use an additional internal LNA. Next week we hope to release our own review of the Prostick Plus, and we’ll hopefully be able to show and explain why some people see better performance with the plus and why some instead see degraded performance.

In his second post Akos shows a tutorial on building an easy helical antenna for Outernet reception. The antenna is constructed from readily available household materials such as a soda bottle, coax cable, electrical tape and a cookie tin. With the cookie tin used he was able to get a SNR reading between 7 – 9 dB, which is pretty good considering that only 3 dB is required for Outernet decoding to work.

Outernet hardware plus the homemade helical antenna made by Akos.
Outernet hardware plus the homemade helical antenna made by Akos.

Two Videos That Show How To Set Up An Outernet Receiver

Outernet is a relatively new satellite based file delivery service which can be received with an RTL-SDR dongle. They continuously send out useful data like weather reports, news, APRS data as well as files like Wikipeda pages, images, videos and books. Previously we posted a tutorial that shows how to set up an Outernet receiver here.

If you instead prefer video tutorials, then two YouTube channels have uploaded Outernet set up tutorials. The first tutorial is by MKme Lab. In this video they set up Outernet using a Raspberry Pi and a Lipo battery for portable operation. Once setup he shows the Outernet browser and weather app in action.

DIY Raspberry Pi Outernet Satellite Receiver Assembly & Testing | #EduCase Project Build

The second video is by John’s DIY Playground and is similar, but goes a bit deeper into setting up the software on the Raspberry Pi and shows how to point the patch antenna towards the satellite.

Outernet satellite receiver using Raspberry Pi

Building a DIY 137 MHz Band Pass Filter

Over on YouTube Adam 9A4QV has uploaded a video showing how to build a DIY bandpass filter for 137 MHz. This can help improve the reception of NOAA and Meteor M weather satellites, by blocking strong out of band signals. Adams design is a 132 MHz – 142 MHz Butterworth bandpass filter which gives about 35 dB attenuation outside of the pass band. He’s also posted a write up documenting the filter design on his website.

Lucas Teske recently went ahead and built the 137 MHz filter suggested by Adam. Lucas didn’t have the correct capacitor values so he ended up cascading several in series. His results showed that the filter did improve his reception significantly.

RTLSDR4Everyone Four New Posts: FlightAware Pro Stick Plus Review, Avoid FlightAware Ripoffs, Review of two BCFM Filters, Getting Started with Outernet

Akos from the RTLSDR4Everyone blog has recently uploaded four new articles. The first article reviews the new FlightAware Prostick Plus. The Prostick Plus is an RTL-SDR dongle optimized for ADS-B reception. It contains a LNA and 1090 MHz filter on board the dongle. In his review Akos tests the FlightAware Prostick Plus and compares it against the regular Prostick with external filtering. His results show that the Prostick Plus gets 18.45% more position reports and 5.4% extra max range in his location. His second post continues with the Prostick topic and warns customers to look out for sellers reselling, or relisting the Prostick for much higher ripoff prices.

FlightAware Prostick vs Prostick Plus
FlightAware Prostick vs Prostick Plus

In his third post Akos reviews our RTL-SDR.com broadcast FM filter and compares it against another similar filter from another seller. His test results show that both filters can improve performace.

Two BCFM band stop filters tested by Akos.
Two BCFM band stop filters tested by Akos.

Finally in his fourth post Akos writes a tutorial on getting started with Outernet reception. He bought the full Outernet bundle which comes with a battery bank, CHIP single board computer, E4000 with bias tee RTL-SDR, LNA with filter and patch antenna. His post describes what each component is, then shows how to use them to receive Outernet. His results also seemed to show that our V3 dongle significantly outperformed the E4000 dongle at Outernet reception. The V3 received the Outernet signal with a SNR of 6.39 dB vs only 2.58 dB with the E4000.

Some Outernet Components
Some Outernet Components