Category: RTL-SDR

Some Tests on our BCAM and BCFM Filters

Over on YouTube user ElPaso TubeAmps has uploaded a video showing his tests on our broadcast AM (BCAM) high pass and broadcast FM (BCFM) band stop filters. These two filters are designed to block broadcast radio signals which in some locations can be extremely strong. If they are very strong then they can overload your SDR which causes very poor performance, even on other frequencies.

Some possible solutions for reducing overloading include:

  1. Attenuation – reduce all the strength of ALL signals coming in.
  2. Increase SDR dynamic range – purchase a higher end SDR with more ADC bits as these can handle strong and weak signals coming in together much better.
  3. Filtering – reduce the signal strength on the problematic frequencies that are causing overload, or only allow your frequency of interest to pass.
  4. Antenna tuning – use a narrowband, directional and/or differently polarized antenna which reduces the unwanted signal’s strength.

In the video he uses his signal generator and a spectrum analyzer to analyze the output of the filters. His results closely match our VNA results which are posted on the BCFM and BCAM filter product release posts.

RTL-SDR 88-108 MHz Bandstop Filter & 2.6 MHz HPF Broadcast AM Filter Measurements

YouTube Tutorial on Setting up a Soft66IP RTL-SDR

Over on YouTube user Danny Shortwave And Radio DX has uploaded a video showing an overview and tutorial about setting up the Soft66IP RTL-SDR. The Soft66IP is a custom RTL-SDR that is made in Japan by JA7TDO. It is an RTL-SDR with upconverter and LNA built into a box together with an embedded computing platform. We’re not sure what the computing platform is, but it is likely to be something similar to a Raspberry Pi. The computing platform is then used to run an rtl_tcp server, and so via a network cable or WiFi connection the device can be accessed by a remote PC.

On the video Danny gives an overview on what the Soft66IP is, and what features it has. Then later in the tutorial he shows how to SSH into the Linux server on the Soft66IP, set it up for your local network, and then later how to connect to it from a remote PC.

How to setup Soft66IP for your Local Area Network with SDRSharper

New Outernet Hardware “Dreamcatcher”: An RTL-SDR with Embedded Computing Hardware

Over on the Outernet forums Outernet CEO Syed has just released pictures of the latest upcoming Outernet receiver called “Dreamcatcher”. The new receiver is an RTL-SDR, LNA, filter, and embedded Linux capable computing hardware all on board a single PCB. The full specs are pasted below:

  • L-band SAW filter (1525 – 1559 MHz)
  • Two-stage L-band LNA with 34dB gain
  • 0.5 PPM TCXO
  • RF bypass for tuning from 24 – 1600 MHz – use as a regular RTL-SDR!
  • USB ports
  • GPIO forest
  • UARTs, I2C, SPI headers (unpopulated) for driving external hardware
  • Two microSD card holders – for boot and storage!
  • 1 GHz CPU
  • 256 MB RAM Now 512 MB RAM
  • USB wifi dongle (not shown) – STA+ AP mode capable!
  • Lots of LEDs! and Switches!
  • microUSB OTG
  • microUSB power port
  • Audio In/Out
  • Speaker with 1.4 W integrated audio amplifier
  • Fully mainline (4.10) Kernel and (2017.01) Uboot support!
    *** JST battery is being removed

On the Roadmap:

  • armbian/debian support

This is a fully-integrated SDR receiver – RF frontend, SDR, Compute, Wifi – Everything!

Outernet is an L-band satellite service that aims to be a download only “library in the sky”. Currently they are broadcasting from Inmarsat and Alphasat geostationary satellites which can be received from almost anywhere in the world. We have a tutorial on receiving and decoding their signal here. Every day almost 20 MB of data is sent down, and this includes data like news, weather forecasts, APRS, wikipedia articles, books and more. In the future you will be able to pay to upload private files or messages. This could be useful for sending messages to people isolated from cell phone reception, or for operating remote hardware.

Previously Outernet sold a DIY version of their receiver which included an RTL-SDR V3 or E4000 dongle, LNA+filter, a C.H.I.P embedded computer, and a patch antenna. Recently they have changed to their custom RTL-SDR hardware which is called the “SDRx”. The SDRx includes the RTL-SDR, LNA and filter on a single PCB. Over time it seems that they are moving in the direction of integration of all components onto a single PCB and this can be seen in the Dreamcatcher which now also includes the computing hardware. This is especially good news as the $9 C.H.I.P computing hardware has been almost impossible to acquire since its release.

The Dreamcatcher looks to be also not just useful for Outernet, but also for general projects that can be done on embedded hardware as there is a port which bypasses the L-Band filter.

Back in 2014 we posted about the XiOne. This was also to be an RTL-SDR and computing hardware built onto the same PCB. It would have been controlled via a WiFi connection and apps on a smart phone/tablet. Unfortunately the XiOne Indiegogo crowdfunding campaign never reached its target so the project faded away. The Dreamcatcher is somewhat similar in that both are RTL-SDRs with onboard computing hardware and WiFi connectivity.

The Dreamcatcher is not yet for sale, but it is currently under production. From the looks of the discussion on the forums, it looks like it will sell for $149 USD. Outernet have said that they are sending us a review sample, so keep an eye out for the review in the coming weeks.

The Outernet Dreamcatcher: RTL-SDR + LNA + Filter + Computing Hardware on a single PCB.
The Outernet Dreamcatcher: RTL-SDR + LNA + Filter + Computing Hardware on a single PCB.

Some Tests on the LNA4ALL

Over on the SWLing post blog Tony Roper has uploaded his review and testing of the LNA4ALL. The LNA4ALL is a PSA-5043+ LNA produced by Adam 9A4QV in Croatia. It is normally considered as one of the best wideband LNAs for RTL-SDR users as it designed well, built well, runs well and is reasonably priced at 20 Euros.

On his post Tony tests the LNA4ALL and compares his measured gain specs against the claimed gain specs on the LNA4ALL website. At 5V power supply he found that the real vs claimed gains matched quite nicely.

Although the LNA4ALL is only specified to run down to 3.3V, Tony found that he could still get usable performance out of it with only a 1.2V supply. However, the gain was reduced by a few dB’s, and we also assume that the IP3 characteristics would also be sufficiently degraded at the low voltage.

Testing the LNA4ALL with his NASA Engine AIS receiver, he found that the LNA4ALL boosted his reception range from 15nm without the LNA, to 22nm with the LNA, and also tripled his received messages.

Tony's LNA4ALL Gain Comparions
Tony’s LNA4ALL Gain Comparions

Discussion and Review of our RTL-SDR Blog Broadcast AM High Pass Filter

Early last month we released a new broadcast AM high pass filter product. The goal of the filter is to block out extremely strong broadcast AM signals (and other problematic LF/MF signals) in order to prevent an SDR from overloading. This is especially needed if you live close to AM towers.

Over on the Utility DX Forum files section, reviewer D. B. Gain has written an excellent review of our broadcast AM high pass filter (pdf), also explaining why and in what situations it might be needed. In the review he explains how broadcast AM propagation works, and how it can change from day to night. He also explains how devices with diode switches (used for switching RF circuits such as filter in and out electronically) can easily overload and contribute to IMD within the switches themselves. This is why a filter without any diode switches in front of it is usually the best solution for reducing strong RF energies.

In the review he then goes on to test the filter, showing some screenshots of the reduction is AM signal strength.

Creating a RTL-SDR NOAA Weather Radio Audio Streamer in Linux

On his blog leander has added a post which shows how he has set up a icecast streaming solution together with an RTL-SDR dongle which is receiving live NOAA weather radio. The idea is to give a computer with no soundcard the ability to stream compressed NOAA weather audio over a network. To do this he uses ezstream, icecast2 and lame. Streaming like this is great if you only want to listen to a single radio channel, and want a low bandwidth solution. Something like rtl_tcp streams the entire raw IQ data across the network which can use huge amounts of bandwidth. Streaming only MP3 audio is significantly more efficient.

First the RTL-SDR is set up to receive NOAA weather audio with rtl_fm. The audio is output to stdin, which is then sent to lame for encoding and MP3 compression. Next ezstream is set up to stream the encoded MP3 data via icecast. Now any PC on the network can use VLC or a similar program to connect to the stream and listen in.

Receiving the stream with VLC
Receiving the stream with VLC

YouTube Videos: NOAA Satellite Tutorial and Building a Radio Telescope

Over on the Thought Emporium YouTube channel the team have uploaded two videos that may be of interest to radio hobbyists. The first video shows a nice overview about receiving NOAA weather satellite images. They explain everything from scratch for complete novice, so the videos are great for almost anyone to watch and learn about radio and SDR concepts. The blurb of the first video reads:

Over the past 2 months, me and my friend Artem have been building antennas to receive signals from weather satellites as they pass overhead. This video chronicles our progress through this project and goes through some of the science involved in working with radio and receiving transmissions. We explore how dipoles work and how to build them, and how we built our final double cross antenna. We used an SDR (software defined radio) called a HackRF to do the work of interpreting the received signals and then decoded them with some special software. We pulled images from 4 satellites: NOAA 15, 18 and 19 as well as METEOR M2. The satellites broadcast immediately as they take the images and no images are stored, so we’re likely the only ones on earth with these images.

How to Pull Images from Satellites in Orbit (NOAA 15,18,19 and METEOR M2)

The second video is about building a radio telescope. Like the NOAA video, they explain all concepts in a simple and easy to understand way, so that anyone even without any radio knowledge can understand what the project is about. In the video they also show how they use a 3D printer to create a tracking mount which can point a satellite dish. They then use the dish to create a satellite heat map. The blurb reads:

Over the last 2 months me and my friend Artem (you met him in the last video) built our first radio telescope. It was built mostly out of off the shelf components, like a satellite dish and Ku band LNB, as well as some parts we 3d printed. When all was said and done we had a system that could not only take images of the sky in radio frequencies (in this case 10-12ghz), but could also be used to track satellites. With it, we were able to see the ring of satellites in geosynchronous orbit, over 35,000km away, This is only the first of what I suspect will be many more telescopes like this. Next time we’ll be building ones that are far larger and can see things like the hydrogen lines so we can image the milky way.

How to Build a Radio Telescope (See Satellites 35,000km Away!)

welle.io: A New RTL-SDR & Airspy DAB/DAB+ Decoder Available for Windows/Linux

Thanks to Albrecht Lohofener for submitting to us his new software package called ‘welle.io’ which is a free DAB and DAB+ decoder and player that supports the RTL-SDR (directly or also via rtl_tcp) and Airspy software defined radios. The software can be run on both Windows and Linux, and also supports Raspberry Pi 2/3 and cheap Chinese Windows 10 tablets.

Albrecht writes that his software is a fork of the qt-dab codebase, with the development goal being to create an easy to use DAB/DAB+ software receiver. The software is still under heavy development, and Albrecht mentions that he is looking for fellow developers and testers to help improve the software and report any bugs. Albrecht writes:

I’m proud to introduce a new open source DAB/DAB+ reception application welle.io https://www.welle.io. welle.io is a fork of qt-dab http://github.com/JvanKatwijk/qt-dab (old dab-rpi and sdr-j-dab) with the goal to develop an easy to use DAB/DAB+ reception application. It supports high DPI and touch displays and it runs even on cheap computers like Raspberry Pi 2/3 and 100€ China Windows 10 tablets. As input devices welle.io supports rtlsdr and airspy.

Currently daily Windows binary builds are available over on the projects GitHub. For Linux and Raspberry Pi users you’ll need to compile the code from source, but in the future he plans to provide Ubuntu snaps.

We gave the welle.io software a brief test and it ran as expected. There is an automatic channel scan feature which scans through all the possible DAB channels and an advanced mode for seeing technical information such as the frequency, SNR and error rates. The software also has a nice touchscreen friendly GUI which automatically downloads and displays the DAB/DAB+ program guide information.

Welle.io DAB/DAB+ decoder for the RTL-SDR and Airspy.
Welle.io DAB/DAB+ decoder for the RTL-SDR and Airspy.