May 22, 2013

E4000 Gain Mod now Available on Windows

One of the advantages of using Linrad on Linux used to be the ability to use a modified rtlsdr.dll file with improved sensitivity gain settings for the E4000 tuner. This mod added the following settings.

AGC mode.
Compromise. This is the gain settings available in the rtl-sdr library as of October 2012.
Linearity mode. For use without filters in environments with strong signals. Low front end gain and high gain after filters.
Sensitivity mode. For use in rural locations or when filters and preamplifiers are placed between the antenna and the dongle. High front end gain and low gain after the filters.

Here is a Reddit thread discussing the improvements, and showing how to apply them to Linrad.

Now Reddit user rtlsdr_is_fun has ported this mod to Windows, and has written an SDRSharp plugin that enables the modified E4000 gain modes via rtl_tcp. This means you will need to run rtl_tcp first, and then connect to it using the RTLSDR / TCP option in SDRSharp. This mod also enables direct sampling for rtl_tcp.

There is a thread discussing the mod here, and you can download the mod from rtlsdr_is_fun’s webpage.

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May 21, 2013

RTL-SDR for Budget Radio Astronomy

With the right additional hardware, the RTL-SDR software defined radio can be used as a super cheap radio telescope for radio astronomy experiments such as Hydrogen line detection, meteor scatter and Pulsar observing.

Hydrogen Line

Marcus Leech of Science Radio Laboratories, Inc has released a tutorial document titled “A Budget-Conscious Radio Telescope for 21cm“, (doc version) (pdf here) where he shows:

Two slightly-different designs for a simple, small, effective, radio telescope capable of observing the Sun, and the galactic plane in both continuum and spectral modes, easily able to show the hydrogen line in various parts of the galactic plane.

He uses the RTL-SDR as the receiving radio with an LNA (low noise amplifier) and a couple of line amps, a 93cm x 85cm offset satellite dish (potential dish for sale here, and here), and GNU Radio with the simple_ra application. In his results he was able to observe the spectrum of the Galactic Plane, and the Hydrogen Line. Some more information about this project can be found on this Reddit thread.

Here is a link to an interesting gif Marcus made with his RTL-SDR, showing a timelapse of recorded hydrogen emissions over 24 hours. Reddit user patchvonbraun (a.k.a Marcus Leech) writes on this thread an explanation of what is going on in the gif.

Interstellar space is “full” of neutral hydrogen, which occasionally emits at photon at a wavelength of 21cm–1420.4058Mhz.

If you setup a small dish antenna, and point at a fixed declination in the sky, as that part of the sky moves through your beam, you can see the change in spectral signature as different regions, with different doppler velocities move through your beam.

This GIF animation shows 24 hours of those observations packed into a few 10s of seconds.

And here is just one of his many resulting graphs shown in the document showing the Hydrogen line.

A similar radio astronomy project has previously been done with the Funcube. More information about that project can be found in this pdf file. In that project they used the Funcube, a 3 meter satellite dish and the Radio Eyes software.

However, in this Reddit post patchvonbraun explains that the Funcube’s much smaller bandwidth is problematic, and so the rtl-sdr may actually be better suited for radio astronomy.

This image is from the Funcube project document.

Another related project is the Itty Bitty Telescope (IBT), which does not use SDR, but may be of interest.

Meteor Scatter

Meteor scatter works by receiving a distant but powerful transmitter via reflections off the trails of ionized air that meteors leave behind when they enter the atmosphere. Normally the transmitter would be too far away to receive, but if its able to bounce off the ionized trail in the sky it can reach far over the horizon to your receiver. Typically powerful broadcast FM radio stations, analog TV, and radar signals at around 140 MHz are used. Some amateur radio enthusiasts also use this phenomena as a long range VHF communications tool with their own transmitted signals. See the website www.livemeteors.com for a livestream of a permanently set up RTL-SDR meteor detector.

In Europe typically the Graves radar station can be used for meteor scatter experiments. Graves is a space radar based in France which is designed to track spacecraft and orbital debris. If you are in Europe you can also make use of the Graves radar simply by tuning to its frequency of 143.050 MHz and listening for reflections of its signal bouncing off things like meteors, planes and spacecraft. Since Graves points its signal upwards, it’s unlikely that you’ll directly receive the signal straight from the antenna, instead you’ll only see the reflections from objects.

In other countries old and distant analogue TV stations can be used or FM transmitters can also be used.

To set meteor scatter up, simply use an outdoor antenna to tune to a distant transmitter. It should be far enough away so that you can not be receive the transmitter directly, or the signal should be weak. If you detect a meteor the signal will briefly show up strongly at your receiver. Performance can be enhanced by using a directional antenna like a Yagi to point upwards at the sky in the direction of the transmitter.

We have several post about meteor scatter available on the blog here. Read through them to get a better understanding of the ways in which it can be monitored. You may also be interested in Marcus Leech’s tutorial where he uses the RTL-SDR to detect forward meteor scatter. (doc here) (pdf here)

Pulsar Observing

A pulsar is a rotating neutron star that emits a beam of electromagnetic radiation. If this beam points towards the earth, it can then be observed with a large dish antenna and a radio, like the RTL-SDR.

Pulsars create weakly detectable noise bursts across a wide frequency range. They create these noise bursts at precise intervals (milliseconds to seconds depending on the pulsar), so they can be detected from within the natural noise by performing some mathematical analysis on the data. Typically a few hours of data needs to be received to be able to analyze it, with more time needed for smaller dishes.

One problem is that pulsar signals can suffer from ‘dispersion’ due to many light years of travel through the interstellar medium. This simply means that higher frequencies of the noise burst tend to arrive before the lower frequencies. Mathematical de-dispersion techniques can be used to eliminate this problem enabling one to take advantage of wideband receivers like the RTL-SDR and other SDRs. The more bandwidth collected and de-dispersed, the smaller the dish required for detection.

Pulsar detection requires some pretty large antennas, and a good understanding of the techniques and math required for data processing so it is not for the beginner. See the previous Pulsar posts on this blog for more information.

If you enjoyed this tutorial you may like our ebook available on Amazon.

The Hobbyist’s Guide to the RTL-SDR: Really Cheap Software Defined radio.

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May 20, 2013

HackRF SDR Giveaway

HackRF is an upcoming open source DARPA funded ~$300 software defined radio that has both transmit and receive capabilities. It has a 100 MHz to 6 GHz range, 20 Msps sample rate, 8-bit resolution, and 500 beta units are about to be given away for free by greatscottgadgets. A good introduction to the HackRF can be found here, and on this wiki here.

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May 20, 2013

RTL_TCP Block for REDHAWK

An rtl_tcp source block for the REDHAWK software defined radio framework has been released. REDHAWK is a framework similar to GNU Radio, which allows the graphical development of signal processing algorithms for software defined radios.

The RTLTcpSource can be downloaded from here.

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May 20, 2013

SDRSharp Frequency Manager + Scanner v1.31 Update

The SDRSharp Frequency Manager + Scanner plugin has just been updated to version 1.31. Scanning is now extremely fast.

Scanner

All scanning now uses automatic tuning based on peak signal strength. Mode and squelch do not matter; only the signal strength is used for tuning.

A completely re-written scanning engine now provides higher performance than in previous versions.

On my equipment frequency range scans average a speed of 782 MHz scanned per second. When the wind is blowing right I have reached 918 MHz per second!

On my equipment group scans average a speed of 161 “channels” per second!

The new watchdog timer will force the scanner to resume scanning after a defined period of time.

A new Hold/Release button lets you pause the scanner to stay on an interesting frequency.

You can now mute the audio while scanning.

There is a new window for editing scanner configuration and for tuning its performance to suit your equipment.

The last selected scan group, defined scan frequency ranges, and all other scanner configuration settings are now stored as your defaults for use the next time you start SDR#.

A built-in benchmark utility tells you how fast the scanner is running on your equipment.

Frequency Manager

Tuning Helper is now disabled by default.

Browse Window

“Clear” buttons on the Filter by Group and Filter by Flagged/Locked dropdowns.

See the Reddit release thread here, and the Yahoo Groups release thread here.

Download from http://www.sdrsharpplugins.com.

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May 19, 2013

Satellite Receive Station with RTL-SDR and Raspberry Pi

Unfortunately the blog referenced in this post is now gone. We have changed all links to ones archived by archive.org.

Over on the carpcomm blog, the author has posted a how to guide on building a remote satellite receive station using the Raspberry Pi and a $20 rtl-sdr dongle or funcube. He uses his own opensource CarpSD software which allows the station to be accessed directly via the web.

Space and satellites are something that only few people are fortunate enough to interact with. However, this is starting to change due to the rapid growth in capability of consumer electronics. In fact, you can receive and decode transmissions from satellites using only a Raspberry Pi, a USB software-defined radio receiver, and a few other cheap parts.

For the software, we'll use the CarpSD ground station control software. It's an open-source program with the source hosted on GitHub. It runs as a background process and connects to the Carpcomm server, so that you can control your station from the Carpcomm website. Thus, there is no need to connect a display to your Raspberry Pi and you can leave your station running continuously in the background. The instructions below can be executed entirely over SSH.

Check out the rest of his post here.

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May 19, 2013

RTL-SDR and Ham It Up In a Box

On the thisisnt.com blog, the author has posted about his project where he placed the rtl-sdr dongle, and a ham-it-up upconverter together into a metal box. This helps with shielding out interference, and also in helping to tidy up the cabling.

See more about his project here.

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May 18, 2013

List of SDRSharp Plugins

There are a number of SDRSharp plugins that extend its functionality. Here is a collection of all the plugins and download links that I could find.

With modern SDR# installing a plugin is usually a simple matter of copying the plugin files to a subfolder within the SDR# Plugins folder. SDR# should automatically recognize the plugins.

Some plugins might require editing the Plugins.xml file with a text editor such as notepad. These plugins will contain a readme.txt or magicline.txt file that shows what line to add to the Plugins.xml file. Just copy and paste the plugin .dll into the SDR# folder and add the magicline line to the plugins.xml file to install the driver.

We note that SDRSharp can now be downloaded with a community plugin package, which includes many of the plugins listed below. However, sometimes some plugins get broken with newer SDR# versions, so if you have issues with the SDR# community edition, it may be wise to download the vanilla edition and install plugins manually.

Frequency Manager + Scanner and Scanner Metrics and Frequency Entry Package

This is a plugin package which comes with three plugins. It comes with a more advanced frequency manager than the one shipped with SDRSharp.

It also has a scanner option which can quickly scan through a group of your saved frequencies, looking for an active signal.

It also has a scanner metrics plugin, which records frequency activity to a database. Later this database can be analyzed to find out which frequencies are the most active, saving you time searching manually for active frequencies.

Finally, this package also has a frequency entry plugin, which works like the old SDRSharp frequency entry used to work. Basically, it just allows you to choose a center frequency and IF frequency easily by typing it in instead of adjusting it with the mouse.

Download the installation packager here

Fast Scanner

Similar to the Frequency Manager and scanner plugin in that it automatically tunes to active signals above a certain power.

~~Download Link~~ (Original website now dead)

Download Link (via archive.org)

Download Link (RTL-SDR Blog Mirror)

Simple DMR

A simple DMR decoder plugin. No external dependencies, no settings, uses SDR# audio path. Designed for listening to unencrypted DMR channels.Mixes voice from both slots into one channel.

Hydrogen Line

Meteor Scatter

Pulsar Observing

Frequency Manager + Scanner and Scanner Metrics and Frequency Entry Package

Fast Scanner

Simple DMR

DDE Plugin

QPSK Demodulator

DDE Tracking and Scheduler Plugin

Gpredict Connector

SDRSharp Net Remote

CTCSS Detector and Squelch

DCS Detector and Squelch Plugin

TimeShift SDR

Digital Audio Processor

Audio Processor

IF Notch Plugin

Simple APCO 25

RDS Logger

DSD+ GUI Interface

TETRA Decoder

AUX VFO

Audio Waterfall Plugin

PAL/SECAM TV Plugin

Modified Baseband Recording Plugin

Modified Audio Recording Plugin

IF Recorder Plugin

Level Meter Plugin

CSVUserlistBrowser SDR# Plugin

MPX Output Plugin

Radio Sky Spectrograph Plugin

Aviation band 8.33 Calculator Plugin

Frequency Lock Plugin

Unitrunker Serial Based Trunking Plugin

Passive Radar Plugin

IF Average

Contour Shuttle Support

Visual Tuner Knob

Audio Streaming TCP Server

CalicoCAT Serial CAT Control Plugin

Heatmap Generator Plugin

Magic-Eye Plugin

Multimon-ng Launcher Plugin

RDS Groups to RSDSpy .spy Format File Plugin

Tetra demodulator utils plug-in

Signal diagnostics logger plugin

SDRSharp FFT peek hold plug-in

TETRA demod plug-in network info grid data logger

TETRA plug-in UDP raw data logger with Python

Front End Plugins

Modified R820T FrontEnd with Manual Control and Decimation

File Player

E4000 Gain Mod Enabler

Plugins that no longer work

Orbitron Plugin (Not working with 1400+)

Easy Scanner Plugin (Not working with 1400+)

Audio FFT Plugin (Not Working with 1400+)

ScopeView Plugin (Not working with 1400+)

Simple Audio EQ Balance Plugin (Not working with 1400+)

Signal Strength Logger (Not working with 1400+)

SDR# short-wave.info Plugin (Not working with 1400+)

GlobalTuners SDR# Plugin (Not working with 1400+)

Unitrunker Trunking Plugin (Not working with 1400+)

AutoTuner Plugin (Out of date)

ADSB# Plugin (Missing)

Modified ScopeView Plugin (Missing)

SDR# Dark Mode Plugin

FFT Grabber Plugin

Accessibility Plugin

ExtendedFFT Plugin

Toolbar Plugin

Other Semi-Related

TVSharp

Other Plugin Lists