Improved digital voice P25 decoding with DSDPlus

December 31, 2013 by314 Leave a comment

We previously posted about the DSD digital decoding software and it’s usefulness with the RTL-SDR dongle and other signal sources. Now there’s a newly released version known as DSDPlus which promises to deliver improved decoding and clearer audio of unencrypted APCO Project 25 (P25) radio signals.

This program is designed to be used with your RTL-SDR receiver software such as SDR#, with the receiver’s output piped to the DSDPlus program using a program such as Virtual Audio Cable or similar. Unfortunately, DSDPlus is a Windows-only offering at this time, and the anonymous author isn’t releasing the source.

DSDPlus is available for download from MEGA. You can find more the program user guide in the README file.

Via http://dangerousprototypes.com

rtl-sdr

RTL-SDR transformer mod e4000 and r820: “H16105DF” 10/100Mbps Ethernet decoupling transformer

Image December 31, 2013 by314 Leave a comment

Some time ago I’ve tried the HF Mod (aka Direct Sampling Mod) on one of my dongles. The simplest way of doing it is by connecting one of the RTL2832U’s ADC (pin 1 or 2) inputs to an antenna which is exactly how I started. Shortly after that mikikg told me about using a transformer in order to generate a differential signal for the ADCs differential input, as well as boosting the signal and matching impedance. As a quick and dirty solution I desoldered a H16105DF 10/100Mbps Ethernet decoupling transformer from an old ADSL modem and used it. It actually matches the frequencies we care about quite well and in addition serves as a low pass filter. At the moment it is used in a 1:1 configuration, though 1:2 will probably perform better, thus I plan to try that as well. Using it together with an antenna made from a few meters of litz I receive many AM radio stations as well as lots of other signals.

Update:
Since someone over at reddit claimed that mikikg originally came up with using Ethernet transformers for the mod, implying I wouldn’t credit him properly, I feel like clarifying. On 10/3/12 I sent him a mail explaining that I had tried a variation of the HF-Mod using an Ethernet transformer and that the results were promising, I also attached a picture to that mail. Seemingly we then both blogged about it quite a while later, yet he did so before I did.

Update #2:
I have tried using the transformer in a 1:2 configuration and the signal actually got worse. That makes me wonder about the RTL2832U’s input impedance.

rtl-sdr, Software

List of SDRSharp Plugins from rtl-sdr.com (thank you guys :D)

December 31, 2013 by314 Leave a comment

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. The installation of most of these plugins will require editing the SDRSharp.exe.config file with a text editor such as notepad. More detailed instructions are usually bundled in a readme file with the plugin.

Unitrunker Trunking Plugin

Allows the trunking control software Unitrunker to control the frequencies in SDRSharp. This allows digital and analogue trunking systems to be followed.

Download Here

Orbitron Plugin

Allows the Orbitron satellite tracking software to control the frequency in SDRSharp. This is useful as Orbitron can automatically correct for the Doppler shift when listening to satellites.

Download Here

Mirror At the bottom of this page

Frequency Manager + Scanner and Scanner Metrics and Frequency Entry Package Plugin

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

Easy Scanner Plugin

Another scanner plugin similar to the scanner already shown above. Add frequencies to the database, then use the scanner to automatically find an active signal.

Download from the files section of this Yahoo group. (You will need to register first)

AutoTuner Plugin

Automatically tunes to signals that appear in the spectrum which are above a certain adjustable signal strength. Can also create null areas to prevent automatically tuning to unwanted signals. There seems to be only an outdated version, which is built in to an old version of SDRSharp available.

Download Here

Fast Scanner Plugin

Similar to the AutoTuner plugin in that it automatically tunes to signals above a certain power.

Download Link (Note this site is in Russian, but has a Google translate option at the top of the page. The download link is at the end of the article)

ADSB# Plugin

Runs the ADSB# ADS-B decoding program as a plugin in SDRSharp. The main advantage to using this plugin is that you get to visually see the waterfall whilst decoding. It also adds a 1-bit CRC error check.

Download from the files section of this Yahoo group. (You will need to register first)

DDE Plugin

Allows programs like WXTrack to work with SDRSharp through a DDE interface.

Instructions and Download Link Here.

Audio FFT Plugin

Adds a audio FFT display in the plugin window.

Download Here

ScopeView Plugin

Adds a simple audio scope to the plugin window.

Download Here

A modified version of the scope view plugin with Decimation, HoldOff and Hold options resides in the SDRSharp Yahoo group files section under the name TXmonitorScopeView.zip (you will need to join the group first to download).

Download Here