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If you have overruns like "OOOOoo There's photos of the E4ks up at easy beginner wood turning projects zoom top of the page and of an RT based dongle in the "mini" format off to the left most minis do not have eeproms for device ID. Both projefts PVC pipe, tools like drills, 8mm drill bits and smaller sub-drill bit, hand saws, files, and potentially a welder though liberal J-B Weld would probably work. CrazyCat's tune-s2 supports Diseqc switches and addressing. When a browser renders a webpage, it does not simply render the webpage HTML.

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Earnings, Stocks. Videos, Auto. They still have unknown phase shifts and sampling time differences relative to each other. This is calibrated by disconnecting them from antennas and connecting every receiver to the same noise source.

Cross correlation of the noise gives their time and phase differences so that it can be corrected. Currently the signal is received and processed in short blocks with each block starting with a burst of calibration noise.

As I understand it the switch chips are sa that "look" for dongle i2c traffic. There are controlled by two RC delay circuits so that every time you change frequency causing i2c traffic it disconnects antennas, waits for some time, feeds a pulse just one edge from the logic chip into all dongles, waits a bit more and connects the antennas back.

You can see the evolution of his setup from this earlier prototype to this later prototype and finally the version used in his direction finder. Every time you tune any two or more dongles to a new frequency there will be a tiny difference in the frequency each actually tuned to.

The offset must corrected before trying to correlate them. If you don't it'll look like there's a constantly varying phase shift. Also don't forget to let the dongles warm up to equilibrium otherwise this additional temperature related frequency shift will cause changes even larger than relative tuning offset and you'll get the "random" phase shift again.

As of Piotr Krysik's " Multi-RTL " github has made maintaining coherence of multiple dongles accessible even to the amateur. His GNU Radio block handles all the complex details of keeping multiple rtlsdr coherent even when they're tuned to different frequencies and over re-tunes. It requires no external circuitry. You just have to distribute the clock signal with cable.

On the clock coherencey side Michele Bavaro's has explored, tweaked, and replaced, librtlsdr's pll setting code, intermediate frequency, and PLL dithering settings, such that the math, and results, work out cleaner.

Using this modified driver he was able to minimize frequency setting errors and improve his GPS carrier following code. Without dithering you can only tune to increments of With dithering, you can tune to aproximately anything.

In the absence of any useful information about the RTLU clock here's some information about the RT's clock system. Crystal parallel capacitors are recommended when a default crystal frequency of 16 MHz is implemented. Please contact Rafael Micro application engineering for crystal parallel capacitors using other crystal frequencies.

For cost sensitive project, the RT can share crystal with backend demodulators or baseband ICs to reduce component count. The recommended reference design for crystal loading capacitors and share crystal is shown as below. When you see something weird, like commercial FM broadcasts at 27 MHz, what you are seeing incomplete filtering of mixing products. It's the harmonics of the square wave driving the mixers combined with insufficient rf filtering to suppress the response.

Sometimes local signals can be powerful ie, pagers or close enough to make the preamplifier behave non-linearly resulting in intermodulation.

For this kind of RFI turning down the gain helps. The tuners all have a certain amount of intrinsic noise too. The But not everything is a ghost from hardware design problems. Depending on your computer setup and local electronics there could be a lot of "real noise"; LCD monitors are a common culprit for VHF noise spikes distributed across wide ranges. It is best to shield and put ferrites on everything if you can. To solve the commercial FM mixing problems an FM trap can be used.

Commercial ones work fine typically. But for non-commercial FM RFI like emergency services and pagers custom filters must be made or ordered. Adam-9A4QV has a detailed write-up on making FM trap with a very high upper passband all the way to 1. Like Adam's it has the unique feature of not also wiping out harmonics of the FM band: fm-notch.

For more information on this general type of coaxial cable notch filter check out Ed Loranger's write up on VHF Notch filters photo. Acinonyx describes one way to doing this using a single strip of aluminum tape combined with a spring to connect it to the dongle ground.

Akos Czermann at the sdrformariners blog made a somewhat confusing but definitely empirical comparison of noise levels compared to different hardware mods like disconnecting the USB ground from the rtlsdr ground. Quite a few people have had success with that and scotch tape around the USB connector works to test it.

Some others bond the enclosure to both the antenna and the USB shield and this works reliably and well. Martin from g8jnj. Additional noise comes from the switching power supply in the RTLU that runs at 1. This drops the supplied 3. In the example linked above ttrftech uses power form the far side of the board but the eeprom's power rail would also work. This decreases spurs in HF significantly. Around this USB cable I clip on 5 or 6 ferrites at each end. I've also written up a seperate, longer, page on the challenges and solutions when implementing broadband antenna.

When I want to do some scanning that takes advantage of the tuner's very wide ranges I use five types of antenna: discone, spiral, dual planar disks, vivaldi tapered slot , and horns TEM and pyramidal. Discone, dual planar disk , and archimedian spiral antenna can omnidirectionally cover almost the full range of the E tuner but things get a bit too large to go all the way to the 24 Mhz of the RT.

You can refer to the seperate spiral antenna page for construction and technical details. To build my discone I followed Roklobsta's D. They each have a javascript zoomable interface to load small tiles progressively. An example. But with a band specific helix in a cone reflector helicone many more satellites can be picked up. No LNA was used. When using such broadband antenna, or even a band specific helix, it is possible to pick up powerful out of band signals due to overloading or incomplete mixer filtering.

It's important to identify any extraordinarily powerful transmitters nearbye and filter them out. In my case I have a 50w transmitter at MHz across the street always going full power. I bought a custom tuned 3 cavity notch filter from PAR Electronics. Usually the spectra are much cleaner when using directional and resonant antenna instead of wideband omnidirectionals.

But many directional antenna like helix and log periodic dipoles have very large out of band sidebands on low frequencies not in the designed range. You don't need GNU Radio to use the rtlsdr dongles in sdr mode, but there are many useful apps that depend on it. It automates grabbing the latest of everything from git and compiling. It will also uninstall any packages providing GNU Radio already installed first. I had no problems using Ubuntu These days pybombs is slowly taking over for build-gnuradio but for now this works best.

If you're thinking about trying this in a virtual machine: don't. If you do get it partially working it'll still suck. Install 3. Most gnu radio projects have been ported to it as default. Only a few old things will require 3. An re install looks like this. It might be useful to save the log output for future reference. Then test it. Newer versions, and RT tuners will output slightly different text.

When updating you can just repeat the install instructions which is simple but long. The advantage to repeating the full process is mainly if there are major changes in the gr-osmosdr as well as rtl-sdr. It'll do things like ldconfig for you. If you don't have the patience for a full recompile and there haven't been major gnu radio or gr-osmosdr changes it's much faster just to recompile rtl-sdr by itself.

The instructions to do so are at the osmosdr page. It'll only take a few minutes even on slow machines. Once you have the latest git clone it is like most cmake projects:. This is visualized with keenerd's heatmap. Because the entire bandwidth is summed and saved as one value the the data rate to disk, and spectrogram dimensions are much lower than FFT mode.

Example gnuplot visualization , annotated , and the gnuplot format , and colour palettes used to generate them. If you do a large number of frequency hops, hundreds then the time adds up. On my two computers the RT tuner dongles average about 55 milliseconds per retune and sample cycle.

I sometimes have dongles that'll fail to lock pll and go into a loop. The -e parameter sets a time limit for a run. Combining this time limit with a bash while loop results in pretty low downtime with resiliance to rtlsdr and USB failures. To combine the results from multiple dongles just cat the files together.

But on gnuplots end each new. Additionally you need to set the output spectrogram filename and a pixel width. I find for Mhz 1 MHz that approximately px per MB of file size is required to cover all gaps.

If you used build-gnuradio it'll tell you what this is at the end of the install. When setting the sample rate it is rounded-down to a multiple of Ksps so the decimation math works out. If you have overruns like "OOOOoo Which means that your machine isn't keeping up with the data stream. Sometimes buffering helps, but only if your machine is right on the edge of working properly.

If it really can't, on average "keep up", no amount of buffering will help. If you have overruns like "aUaUaUaUa" or just "aaa" then the audio system is asking for samples at a higher rate than the DSP flow can provide 44vs48Khz, etc. Use "aplay -l" to get a list of the devices on your system. The hw:X,Y comes from this mapping of your hardware -- in this case, X is the card number, while Y is the device number.

Or you can use "pulse" for pulseaudio. Try specifying,. As of August 9th Gqrx 2. This upgraded version can now be installed as binaries with all of it's dependencies pre-packaged on both Ubuntu linux a custom PPA , no That includes all the GNU Radio stuff. So this is an all-in-one alternative to building GNU Radio from source. I think this person's guide is better than mine. As of the changes to Mono 4 allow SDR to be viable to run on linux again. Make sure you have the latest Mono 4 though.

This still requires soft linking in your system rtlsdr and portaudio library to the sdrshape. Just make sure you link your actual system rtlsdr and libportaudio, not my example path above. Roklobsta's rtlsdr. As of July 23, there was a major update to gr-air-modes which now includes a nice google maps overlay and works on gnu radio 3.

Antirezs' ADS-B program is really slick. It does not depend on GNU Radio, has a number of interactive modes, and it even optionally runs it's own HTTP server with googlemaps overlay of discovered planes; no virtualradar needed. It uses very little CPU and has impressive error correction. This is your best choice to play with plane tracking quickly. That is a significant part of the performance improvement. As of this feature was added to the main librtlsdr driver as well.

With the addition of a GPS receiver, this program can be used to obtain basic cellular coverage maps. The author had only tested it on Ubuntu Scanner is very useful to get your dongle's frequency offset reliably and Tracker is very pretty. Remember to let your rtlsdr dongle warm up to equilibrium temperature before checking frequency error. The code was written by Joshua Lackey and made rtlsdr accessible by stevem. There is also a windows build made by Hoernchen.

Let your rtlsdr dongle warm up to equilibrium temperature before running the test. When you're using this to find your frequency error it's important to use the -e option to specify intial error.

I compiled some install process and example usage notes. I wrote these scripts do automatic generation of 1D spectrograms, per frequency time series plots of total power, and 2D spectral maps over arbitrary frequency ranges using multiple dongles at once.

There is almost no DSP done and it is very simple but the wideband spectrograms and time series can be informative and fun regardless. It uses gnuplot for graphics generation.

It has a graphical stripchart display, and a standard FFT display. It also records both total-power and spectral data using an external C program that records the data along with timestamps based on the Local Mean Sidereal Time. This is another incredible tool by patchvonbraun. It does all the heavy lifting of integration over time and signal processing to get an accurate measurement of absolute power over a range.

With it he has managed to pick out the transit of the milky way at the neutral hydrogen frequency using rtlsdr sticks and a pair of yagi antenna.

Don't forget to set the --devid to rtl otherwise gnuradio won't find the gr-osmosdr source and it'll substitute a gaussian noise source. Ear to Ear Oak made this wideband total power scanner that generates 1D spectrum plots over any tunable ranges with arbitrary integration times.

It can update a matplotlib python plot GUI in real time and has the ability to output cvs values as well as an internal format. It's very useful for finding what's broadcasting in your area quickly.

Using it's csv output and gnuplot I visualized a scan from MHz. If you want to use the data in gnuplot you have to sort it and make sure the header is commented out. You can comment out the header manually but I instead prefixed a hash to the log writing behavior at line ,. Automatic generation of and html gallery creation of wideband spectrograms using multiple rtlsdr dongles to divide up the spectrum.

It also produces narrow band total charts, and other visualizations. These scripts cause the rtlsdr dongle to jump from frequency to frequency as fast as they can and take very rough total power measurement. This data is stored in human readable logs and later turned into wideband spectrograms by calling gnuplot. In order to further increase coverage of any given spectrum range multiple instances of the script can be run at once in the same directory adding to the same logs.

Their combined output will be represented in the spectrogram. I don't know much python but the python wrapper for librtlsdr pyrtlsdr was a bit easier to work with than gnu radio when I wanted to do simple things without a need for precision or accuracy. Actualy receivers with processing could be made with it too, but not by me.

This is the gist of what it does,. I have used the " test. Since I am not very good with python I had to pull a lot of the logic out into a perl script. So everything is modular. As of now the python script generates the spectrogram pngs and records signal strength and metadata in frequency named logs. It is passed lots of arguments.

These arguments can be made however you want, but I wrote a perl script to automate it along with a few other useful things. It can generate a simple html gallery of the most recent full spectral map and spectrograms with each linked to the log of past signal levels.

Or it can additionally generate gnuplot time series pngs example and link those intead of the raw logs. I no longer have it running because of the processor usage spikes which interrupt daily tasks.

Since the hooks? I have probably shown that I don't know anything about python with this description. I apologize for cluttering up the pyrtlsdr namespace with such trivial changes but I'm new to this and github doesn't allow for private repositories.

These two scripts do fast scans within python from x to y frequency. Enabled it with -fast and make sure to set start and stop frequency with -f1 and -f2. Do not use -flist with this option. This is an example output "spectral map" a spectrogram with a silly name. This example output above shows the overloading effects of using a wideband discone that picks up off-band noise.

Each column is made up of small squares colored by intensity of the signal. Since the scripts start at the low frequency and sweep to high there is a small time delay between the bottom and top see it more clearly zoomed in. And this is represented as the slant of the row.

Sometimes strong signals will swamp out others resulting in discontinuities displaying as small dark vertical bands. Only output a large spectrogram of all frequencies to the directory specified with -d2 as spectral-map.

This example does not use frequency offset correct -c for even faster speeds. By splitting up the spectrum into multiple smaller slices and giving them to multiple dongles the time required for one scan pass can be greatly improved. The above spectrogram is made with 2 dongles, one for the lower half and one for the upper.

It is from ryannathans who also contributed the code for for specifying device ID. This is as simple as running the script twice but giving each instance a different "-dev" argument to specify device ID. If they are using the same directory -d2 their log data will be combined automagically for better coverage.

These skew the scale of the output spectrograms. If I notice that they have occurred during a long run I'll use grep to find them and remove them manually. I replace the signal level with the level of the previous non-corrupt sample. In the future I'll build this kind of outlier removal in to the scripts, or sanity check before writing them. I'm slowly putting together an Inline C based perl wrapper for exposing librtlsdr's functions within a perl script to write this as a standalone in perl.

This is slow work because I've never done anything like it before. Then download the two scripts above and put them in the same directory. For large bandwidths sampled this feature, ppm error correction, has an unnoticably small effect but I wanted to add it anyway.

I've disabled the matplotlib python per frequency spectrogram plots for frequencies over 1 Ghz because there's not much going on up there. Also, the x-axis ticks and labels become inaccurate for some reason. The signal strength logs, named by frequency e. In order of columns it is: unix time , relative signal level , gain in dB, PPM correction.

It also generates a log file with all frequencies for use with gnuplot, all. This file has unixtime first, then frequency, then gain and ppm error.

The radioscan. To generate plots and signal strength for 52 Mhz to Mhz with a gain of 30, sample rate of 2. Not all volunteers read for LibriVox. If you would prefer not to lend your voice to LibriVox , you could lend us your ears. Proof listeners catch mistakes we may have missed during the initial recording and editing process. Readers record themselves reading a section of a book, edit the recording, and upload it to the LibriVox Management Tool.

For an outline of the Librivox audiobook production process, please see The LibriVox recording process. We require new readers to submit a sample recording so that we can make sure that your set up works and that you understand how to export files meeting our technical standards. We do not want you to waste previous hours reading whole chapters only to discover that your recording is unusable due to a preventable technical glitch.

A book coordinator commonly abbreviated BC in the forum is a volunteer who manages all the other volunteers who will record chapters for a LibriVox recording.

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