RTL-SDR Blog V3 Arrived

I recently bought a new RTL dongle that supports Direct Sampling that allows frequencies less than 40Mhz. In particular, the model I ordered was the RTL-SDR BLOG V.3. DONGLE that was really cheap compared with other solution. It still can't reach the quality of the other more expensive receivers, but it still a step up. The Dongle comes with a long external antenna.

The RTL dongle.

So, the question now is how better is from my old SDR. I did a check with the RTL power tool to see what is the difference. My old SDR Dongle (Fitipower FC0013) has coverage from 22 to 1100 MHz. The new Dongle RTL Blog V3 a has Rafael Micro R820T has coverage from 24 - 1766 MHz, but it also contains Direct Sampling that allows for High Frequencies. A word of warning here, the reception using Direct Sampling is very bad, especially if you connect the antenna without a filter band or/and preamplifier. I did experiments using the rtl_power, and the results showed much more gain for the new Dongle. All the experiments were done using the internal antenna inside the home. I don't have yet the ferrites installed (post is really slow here), but you can get an idea how the dongles are doing. Here are the plots (click to zoom):

Fitipower FC0013 24-500 MHz Band survey.

RTL Blog Rafael Micro R820T 24-500 MHz Band survey.

However, we should be interested in the Signal Noise Ratio rather to actual power received. The new Dongle is more sensitive, but it also gets more noise. I'm waiting for the ferrite to arrived to get a clear view the noise of the new Dongle. Here is a screenshot receiving HF:

Receiving HF with a lot of noise.

You can buy the receivers here: SDR Blog Receiver with Rtl2832u ADC Chip

Processing Milky Way in RawTherapee

This text is an analysis of a video I did some months ago how to process photos of our Milky Way in RawTherapee. You can find the picture here . The photo was taken by wiegemalt. This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Editing: Step 1: Fixing lighting The first thing someone notices when opening the picture is the extreme noise due to high ISO used (1600 - check the picture on the right). The first thought is to de-noise the picture, however, if you do that you are going to loose the details of the night sky. The main reason for the high noise is the additional exposure Rawtherapee adds when the 'Auto' button is pressed. In particular, the RT adds +2.4 EV to equalize the picture. This is Wrong! What we want is to keep the noise down and at the same time bring the stars up. That's why we are going to play with the Tone Curve of the RT. To adjust the light properly we increase the cont

Static linking with gcc and g++

In this tutorial, we will explain what the static linking is, how this affect the size of final binary, and why statically linking with g++ sometimes is pain. By definition, a statically compiled binary is a group of programmer ‘s routines, external functions, and variables which are packed into the final binary executable. The compiler or the linker produces the final object and embeds all the functions and variables and the linking phase. There are two reasons of using dynamic linking and shared libraries: 1) Avoid creating a huge binary, if all the programs use a standard set of libraries why not having the operating system providing to them 2) Compatibility on operating system and machine dependant characteristics: sometimes the libraries must be implemented based on the architecture or the operating system and using dynamic linking is an easy way to avoid this catch. On the other hand, static linking is the ideal way of distributing one software product, paying

Homemade NAS after two and half years

Few years ago, I created a NAS system using my old PC. The old pc is powerful enough to do the basic NAS operation except real time transcoding of 4K or more than one 1080 streams. The setup was setup as follows: 1 SSD 128 GB for boot device 2x 4 TBs for the main storage configured as RAID 1 The hard disks were from different manufacturers (WD red plus and Segate) to avoid catastrophic situations: disks are part of a bad batch and you will have a second failed disk during the build of the RAID array. Here is a list of my mistakes: My first mistake was CentOS. I wanted a stable machine without surprises, unexpected behavior, as much less bugs affecting my setup. I had three free/open source options: Open Media Vault: Debian based Linux with many configuration options. The main downside is that you don't have support for ZFS and you have to very often use the command line to fix things. Moreover, there are a plethora of open issues/bugs that can make your life harder than expected

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