Updates on the PICTOR Low Cost Open Source Radio Telescope Based on RTL-SDR

Back in July we posted about PICTOR, an open source and RTL-SDR based radio telescope project. The owner of the project recently wrote in and wanted to share some updates. His text is below:

A few months ago, PICTOR was launched. PICTOR is a free to use open source radio telescope that allows anyone to observe the sky in the 1300~1700 MHz range at any time via the easy-to-use online platform.

The goal of this effort is to introduce students, educators, astronomers and others to the majesty of the radio sky, promoting radio astronomy education, without the need of building a large and expensive radio telescope. 

Since the initial launch, PICTOR has gotten lots of updates and improvements, particularly in the software backend, providing more data to the users, using advanced techniques to increase the signal-to-noise ratio by calibrating spectra and mitigating radio frequency interference (RFI) (if present).

Here is an example observation with PICTOR, clearly showing the detection of 3 hydrogen-dense regions corresponding to 3 unique spiral arms in the Milky Way!

Graphs from the PICTOR RTL-SDR Radio Telescope showing the 3 unique spiral arms in the Milky Way.
Graphs from the PICTOR RTL-SDR Radio Telescope showing the 3 unique spiral arms in the Milky Way.

If you’re new to radio-astronomy, the developer of PICTOR has provided a PDF including some introductory radio astronomy information and instructions on how to observe the radio sky with PICTOR: https://www.pictortelescope.com/Observing_the_radio_sky_with_PICTOR.pdf

Using an RTL-SDR to Investigate GPS Interference Problems on Drones Caused By HD Cameras

Over on YouTube Drone and Model Aircraft enthusiast channel Paweł Spychalski has uploaded a video showing how he determined that cheap HD cameras that are commonly used on hobbyist drones can cause locking issues with the on board GPS. He writes:

You might believe it or not (today I will prove it, however) that HD cameras, especially cheap ones, can be responsible for GPS problems on your drones and model airplanes. The majority of HD cameras (RunCam Split, Runcam Split Mini, Foxeer Mix, Caddx Tarsier) generate RF noise on different frequencies. Some of them on 433MHz, some on 900MHz, but most of them also at around 1GHz. Just where one of the frequencies used by GPS signal sits. As a result, many GPS modules are reported to have problems getting a fix when the HD camera is running.

In the video he uses an RTL-SDR and SDR# to demonstrate the interference that shows up when a cheap HD camera is turned on. He shows how the interference is present at almost all frequencies from the ISM band frequencies commonly used for control and telemetry to the 1.5 GHz GPS frequencies.

GPS vs HD cameras - it's all about RF noise

SDR Makerspace Conference to be Held in Switzerland in November

SDR Makerspace is a community based in Greece that is run by the European Space Agency and Libre Space Foundation (who are responsible for the SatNOGS project). It provides funding and resources for Software Defined Radio based space communication projects.

On November 28-29 2019 they are holding the SDR Makerspace Conference in Payerne, Switzerland. The conference is free to register although spaces are limited.

The technical talks during the first day will be:

  • Open-Source SDR Software for Satellite Communications - Alexandru Csete
  • LimeSDR as an enabler for Satellite TV Transmissions - Dave Crump
  • How wide band data converters enable SDR in Satcoms - e2v
  • Teaching SDR: EPFL experience - Bixio Rimoldi
  • Xilinx’s adaptive solutions for SDR application - Georg Hanak
  • SDR Makerspace: Evaluation of SDR Boards and Toolchains - Sheila Christiansen
  • SDR and Amateur radio in space - Michel Burnand
  • SDR Makerspace lightning talks - Multiple Authors

The second day will consist of workshops on using SDRs for satellite communications, and on using the LimeNET Micro and LimeRFE for SDR satcom development.

Exhibitors who will be at the conference.
Exhibitors who will be at the conference.

L-Band Patch Antenna Set Preorder Sale Ending Soon – Shipping Begins Next Week

Just a heads up that the preorder sale on our new L-Band Patch antenna set will be ending October 21 as we are almost ready to ship the units out. After the preorder sale ends the pricing will rise from $34.95 to $39.95 USD.

PREORDER PRICING: 34.95 USD incl. free shipping.

Please see our store to preorder the unit.

Preorder has now ended and shipping will begin shortly. Thank you!

The product is a ready to use active patch antenna set that is designed to receive L-Band satellites such as Inmarsat, Iridium and GPS. It is enclosed in a waterproof plastic case, and can easily be mounted to a window using the provided suction cup and 2M coax extension cable. It can also be mounted to almost anything else using the included flexible tripod legs, or if you prefer, use the standard 1/4" camera screw hole to connect it to any mount that you like.

The antenna is powered via 3.3V - 5V bias tee power, so any bias tee capable SDR such as our RTL-SDR Blog V3 can be used to power it.

In terms of performance see our previous post that announced the product for sample screenshots and reception tips.

The RTL-SDR Blog L-Band Satellite Patch Antenna Set
The RTL-SDR Blog L-Band Satellite Patch Antenna Set
Inmarsat Reception
Iridium Reception

Using a LimeSDR and RTL-SDR to Transfer a Text File Over the Air

Over on his blog nuclearrambo has been working on a project that uses a LimeSDR and RTL-SDR to transfer a small CSV text file over the air.

The transmitting side consists of a GNU Radio flowchart that encodes the text file into a binary string, modulates that binary string with Binary Phase Shift Keying (BPSK), and then transmits it using the LimeSDR.

The receiving side uses an RTL-SDR, and is based on another GNU Radio flowgraph that uses a polyphase clock sync block to synchronize the sampling time, a costas loop for fine frequency correction, an LMS DD equalizer block to compensate for multipath effects, and finally demodulation blocks that recover the bits and text file from the BPSK signal.

His results showed that he can almost recover the entire file except for the first few bytes of data which is always lost since it takes time for the clock sync and costas loop block to converge. The post goes into further detail about what each of the blocks do and some of the signal theory math behind everything. The GNU Radio GRC file is also provided if you want to try it out yourself.

LimeSDR Transmitting a CSV file to a RTL-SDR with BPSK modulation.
LimeSDR Transmitting a CSV file to a RTL-SDR with BPSK modulation.

XYNC: A Massive MIMO SDR with up to 32×32 TX/RX Channels

Back in 2017 we posted about the crowd funding of the Fairwaves XTRX, a small PCIe based TX/RX capable software defined radio that back then cost US$199 (now only the XTRX Pro is available for US$599). The XTRX is based on the same RF chips that are used in the LimeSDR and each unit has 2 x 2 MIMO (multi-input, multi-output), 120 MSPS SISO / 90 MSPS MIMO, 30 MHz to 3.7 GHz tuning range and comes with an on board GPSDO.

Recently Fairwaves have begun crowdfunding a new software defined radio called the XYNC. The XYNC is essentially a motherboard for connecting up to 16 XTRX boards together which results in an SDR with 32 TX and 32 RX channels.

If you’re working on a massive MIMO system or have a large swath of spectrum you need to monitor, XYNC (pronounced iks-sync) is right for you. XYNC builds on the success of the Octopack SDR we offered during the XTRX campaign and takes into account feedback from the original Octopack users.

You can connect two XYNC boards, either to increase the number of RX/TX channels (e.g., two XYNC Octos give you 32 TX and 32 RX channels) or to increase throughput per channel (e.g., two XYNC Quadros give you twice the throughput of a single XYNC Octo). Connecting more than two XYNC boards is also possible, but requires an external clock and 1 pps signal distribution circuitry, neither of which is provided as part of this campaign.

While advertised as low cost, the pricing is probably out of reach for most hobbyists, with the quad 8x8 unit coming in at US$4500 and the top 16 board 32x32 unit priced at US$13,000. Still, these prices are very good for a massively MIMO SDR and pricing is set to rise once the crowdfunding campaign ends in 39 days.

The XSYNC Massively MIMO SDR with up to 32x32 TX/RX Channels
The XSYNC Massively MIMO SDR with up to 32x32 TX/RX Channels

An Easy Windows GNU Radio Setup Guide and Video for the SDRplay

SDRplay have recently posted a new workflow document and video that shows how to easily set up GNU Radio on Windows with an SDRplay software defined radio. They write:

GNU radio is a popular environment for teachers and developers involved in Digital Signal Processing and exploring new radio architectures. For receiver applications, the low cost dongle is a popular hardware choice, but if you need reliable, clean, continuous radio signal reception from 1kHz to 2 GHz (without the need for block converters or external filters) then an SDRplay RSP is a useful alternative.

With help from the GNU radio foundation, SDRplay has now made available a workflow for windows for all its RSP radios: www.sdrplay.com/docs/gr-sdrplay-workflow.pdf

Special thanks goes to Frank Werner-Krippendorf (HB9FXQ) who did the original SDRplay source block development, and to Geof Nieboer who has developed the Powershell scripts which enable operation on Windows.

GNU Radio workflow for SDRplay and Windows

SignalsEverywhere: Testing out NooElecs PCB L-Band Patch Antenna

Over on his YouTube channel Corrosive from the SignalsEverywhere YouTube channel has uploaded a video where he tests out the new US$29.95 NooElec PCB patch antenna for receiving L-band satellite signals. In the video he shows how it can be combined with one of their SAWBird L-band low noise amplifiers in order to receive L-band satellite signals such as Inmarsat STD-C and AERO.

We note that our own RTL-SDR Blog Active L-band patch antenna will be ready to ship out before the end of this month, and while waiting for it we are currently having a preorder sale for US$34.95 including free shipping over on our store. For US$34.95 our patch antenna is fully contained in a waterproof enclosure, includes an LNA built in, and comes with several mounting options, so we believe that it is really a great deal. The patch design is based on the Outernet ceramic patch that was compared against the NooElec PCB patch shown in Corrosives video, so performance will be very similar.

Nooelec NEW Inmarsat Patch Antenna with Airspy SDR