Category: News

New Version of Digital Speech Decoder DSD+ 1.071 Released

The latest version of Digital Speech Decoder+ (DSD+) has just been released, bringing it up to version 1.071. There appears to be no changelog, so we are unsure as to what is new, but one obvious change is that they now include a new program called FMP which is a simple NFM demodulator, similar to rtl_fm, although it does have a GUI with point and click tuning. FMP can be used as a replacement for SDR# or similar software, and is especially useful to use on low end devices such as netbooks.

An active discussion on the latest release of this software can be found in this thread on the forums.

The FMP NFM demodulator tuned to a MotoTRBO signal.
The FMP NFM demodulator tuned to a MotoTRBO signal.

DSD+ is a Windows program which can be used to decode and listen to digital voice protocols such as D-STAR, NXDN4800, NXDN9600, DMR/MotoTRBO, P25 Phase 1, X2-TDMA and ProVoice with an RTL-SDR or other radio. On some DMR systems you may also be able to use the included LRRP software, which allows you to view the GPS locations of broadcasting radios. The last major release was version 1.05.


The DSD+ team are now also offering a “fast lane” early access program, which for a small donation will allow you to have early access to new and upcoming DSD+ features. They aim to release a new update to donators every 7 to 30 days, while stable public releases will continue to be released every 4 to 6 months. The donation costs $10 for one year of early access, and $25 for lifetime updates. Some features they are currently working on include:

  • Better tablet support
  • IDAS/NEXEDGE/Cap+/Con+/TIII trunk voice following
  • Per-call audio recordings
  • Other needed DSD+ upgrades
  • FMP upgrades
    • Squelch
    • Drift tracking
    • Selectable sampling rates
    • Adjustable windows sizes
    • TCP client/server mode (eliminates VAC / VB-C)
    • Multiple VFOs
    • Airspy support

dump978: UAT Decoder for the RTL-SDR + FlightAware App now supports UAT

In most of the world aircraft use the ADS-B standard for location tracking which transmits at a frequency of 1090 MHz. However, in the USA there is the option for aircraft to instead use the Universal Access Transceiver (UAT) protocol which transmits at 978 MHz.

UAT has some extra features for pilots compared to ADS-B. In addition to location information UAT provides a Traffic Information Service (TIS/B) which allows pilots to see what ground control sees on their traditional RADAR system. It also provides a Flight Information Service-Broadcast (FIS/B) which includes weather and other information. It seems that most small aircraft in the USA prefer to use the UAT system due to it’s lower cost and additional features. 

A few months ago an experimental version of dump978 MHz was released which is what we believe to be the first working UAT decoder for the RTL-SDR. It’s still in experimental development, however the FlightAware team have already referenced it for developing their Android ADS-B app which we posted about a few days ago. Because of the work done with dump978, the beta version of the FlightAware Android app has recently been updated and can now support UAT decoding. To download the beta version with UAT you may need to sign up to their public beta. More information about the beta can be found on their Google+ beta testing community page.

FlightAware ADS-B App which now supports UAT decoding.
FlightAware ADS-B App which now supports UAT decoding.

Direct Sampling 14 MHz Low Pass Filter and Galvanic Isolator for the RTL-SDR now for sale in Japan

Previously we posted about Japanese RTL-SDR experimenter Nobu and his work in prototyping a new 14 MHz low pass filter and galvanic isolator for use with the RTL-SDR. The low pass filter improves reception when using the RTL-SDR in direct sampling mode by reducing out of band interference and the galvanic isolator (isolation transformer) reduces computer and other noise when using the RTL-SDR with an upconverter. The products can be bought from the Japanese Amazon store [Galvanic Isolator] [Low Pass Filter], however to purchase from outside of Japan you will need to use a third party shopping service available at If you are interested in Nobu’s products, he also has direct sampling modified RTL-SDR dongles and dongles with 10 ppm crystals available, as well as his own upconverter for sale in Japan.
Galvanic Isolator
Galvanic Isolator
14 MHz Low Pass Filter
14 MHz Low Pass Filter

SDRPlay Price Reduced to $149 USD

The Radio Spectrum Processor (RSP) by SDRPlay is a receive only software defined radio with a 100 kHz to 2 GHz range (with a small gap at 380 MHz to 430 MHz), a 12-bit analogue to digital converter (ADC) (~10.4 ENOB), 8 MHz bandwidth and a bank of several switched front end filters. Previously the SDRPlay RSP was priced at $299 USD, however they have just halved this price down to $149 USD plus tax and shipping. At this price point we think the SDRPlay is a very good competitor to the Airspy SDR which seems to be the more popular option priced at $199 USD, especially if you are interested in listening to the HF bands without the need for an upconverter. Recently we posted about some SDRPlay reviews which are all favourable.
The Radio Spectrum Processor (RSP) by SDRplay.
The Radio Spectrum Processor (RSP) by SDRplay.

SDR# Plugins: Frequency Manager Updated and New RDS Logger Plugin

Recently the commonly used frequency manager plugin for SDR# was updated to version 1.6. The latest version can be downloaded from The updates are as follows:
  • The Frequency Description is now displayed in the upper-right corner of the spectrum analyzer, along with the indicator for multiple database entries for that frequency.
  • As a result of moving the above information to the spectrum analyzer, the Frequency Manager panel is now 35% smaller.
  • The Clipboard Monitor now optionally watches the clipboard for frequencies you might have copied from the internet; and if that can be converted to a MHz value it tunes the radio to that frequency.
  • Function Keys F1-F10 can now be used to tune to a preset frequency.
  • A new Minimum Signal Strength Line is displayed on the spectrum display.  This, along with real-time display of the current signal’s strength when the scanner is running, let you see at a glance how that signal compares to your scanner settings.  In addition you can use customize the line with one of 6 line patterns.
  • Current Signal Strength in dB is displayed in the upper right corner of the spectrum analyzer, just after the Frequency Description.
  • Timeout and Watchdog timers’ indicators are now displayed in the upper right corner of the spectrum analyzer.
Also, on the SDR# Yahoo group discussion mailing list user Andy Pritchard has released a beta version of his new RDS Data Logger plugin for SDR#. This plugin can be used to log Radio Data System (RDS) data on a single frequency or on multiple frequencies by using the scan function. It can be a very useful tool for FM DXers. The plugin is still in beta but can be downloaded now directly from Later versions may be released on the SDR# Yahoo group.
RDS Data Logger SDR# Plugin
RDS Data Logger SDR# Plugin

CubicSDR: New open source, cross platform SDR software

Over on YouTube a video showing off a preview version of a new cross platform and open source SDR software program has recently been uploaded. The software is named CubicSDR and aims to support all major operating systems including Linux, Windows and OSX. The code can be downloaded from its GitHub page at CubicSDR currently supports the RTL-SDR, but in the future hopes to support the HackRF and other SDR’s. They also hope to eventually integrate several demodulation filters, make managing multiple SDRs easy and allow for scripting of custom demodulators.

PortableSDR now on Kickstarter

Back in November, 2014 we posted about the PortableSDR, a 0 – 35 MHz portable software defined radio transceiver that was the third place winner in the Hackaday Prize competition. The PortableSDR project is gaining traction and now has a Kickstarter campaign. They write:
The Portable Software Defined Radio, or PSDR, is an Open Source, Fully stand-alone HF/Shortwave Software Defined Transceiver. It includes a Vector Network Analyzer and Antenna Analyzer as well as GPS. It’s built for rugged portable use. It is designed to be a flexible platform for development, a learning aid, and and a useful instrument for electronics enthusiasts. Features:
  • Coverage from 0 to 35MHz
  • Waterfall display that lets you see radio signals
  • Receives AM, USB (Upper Side Band), LSB (Lower Side Band), and Morse code (CW)
  • Modulates USB and LSB signals
  • Variable bandpass filter
The campaign hopes to raise $60,000 USD to aid in the development of the hardware and software and with the manufacturing process. The kickstarter is offering kits at various stages of completion from $250 to $475 and a fully assembled kit at $499. They note that the current PSDR2 that you will receive from the Kickstarter is still a development version, not the final product. The PSDR2 is missing some key features that will be in the final version like filters and output amplifiers.
The PSDR v.1
The PSDR v.1

We now sell RTL-SDR’s with the R820T2 Tuner and 2x Telescopic Antenna + R820T2 Tests

We now sell R820T2 RTL-SDRs on (currently for US customers only sorry!) and are currently running a $2 off promotional sale which will expire January 31, or until the first batch of stock runs out. Compared to the other choices our RTL-SDR Blog branded units come with several improvements which we list below.
  • Use of the R820T2 tuner which has been shown to have slightly better noise performance and give better SNR compared to the standard R820T chip.
  • Use of improved component tolerances which help the circuit to operate at its optimum.
  • Use of a surface mount 28.8 MHz oscillator instead of the “can” type. We believe this will reduce the PPM offsets to below 30 in most dongles, but note we can not guarantee this.
  • Improved “full braid” coax cable on the antenna base which has significantly lower loss compared to the coax used on other brand RTL-SDR stock antennas.
  • Comes with 2 x telescopic antennas. 1 x 9.5 cm to 31.5 cm telescopic antenna and 1 x 20 cm to 1.5 m telescopic antenna. Great for beginners to receive a wider range of frequencies without buying extra antennas.
  • No IR LED. The IR LED is useless for SDR operation and the long legs on the LED may pick up interference.
We currently have two options for sale that are shown below. The dongle only unit is perfect as a replacement dongle or for those who just want to try out the R820T2 chip. The unit with the two telescopic antennas is great for beginners who don’t have any good antennas already. We also have limited quantities of some MCX male to various female adapter sets for sale which work out to be much cheaper than when buying them individually. Buying a set will have you ready for almost any antenna connection you need. The pigtail adapters come with 20cm of RG316 cable and the straight adapters don’t use any cabling. Pigtail Adapters SetMCX -> Various Female Pigtail Adapter Set – $19.99 Straight MCX Adapters SetClick here to buy a MCX -> Various Female Straight Adapter Set - $16.99 Currently because of the way Amazon works, we can only ship to US customers, but we may ship overseas in the future. Shipping from Amazon is fast and free if you spend over $35 or are a Prime member. Returns from faults are also easy and welcome. If you are overseas and can’t buy from us, the alternatives for R820T2’s are the Nooelec R820T2 (US shipper), the Cosycave R820T2 (ships from Channel Islands, UK) and there are also some Chinese R820T2 (Chinese shipper) models available on ebay. We also offer unofficial support over on our forums. If you do buy from us we hope that you will consider leaving a product review on the Amazon page as that will really help us out as small time Amazon sellers. As an added bonus, we will also have our e-book on sale from January 16 to January 23 at $6.99 USD, reduced from $9.99 USD. We also performed some simple performance tests on the R820T2 which we show below.

R820T2 Tests

The first test was a noise floor test. We used rtl_power and ran a noise test with maximum gain and a 50 Ohm terminator connected for 15 minutes over the entire receivable frequency band. We averaged the results over three different R820T dongles and three R820T2 dongles to remove dongle to dongle variances. The results show that noise floor on the R820T2 is around 2-3 dB lower at most frequencies. R820T2_NoiseFloor Next we tested the SNR with the gain set to zero using a HackRF as the signal source. The results show that the R820T2 is about 2-5 dB more sensitive depending on the frequency. Also, compared to the R820T, the sensitivity seems to be significantly better at 1.5 GHz to 1.8 GHz as all tested R820T units could not even detect the test signal above 1.5 GHz without increasing the gain. R820T2_SNR

Oliver Jowett HF Driver Test

The R820T2 should have better performance at HF frequencies when using the experimental Oliver Jowett drivers. We tested an R820T and R820T2 on broadcast AM reception. At broadcast AM frequencies the R820T starts with a very high noise floor after starting it for the first time, but after about 5 minutes seems to settle down to a lower noise floor shown in the right image below. In comparison the R820T2 starts at a low noise floor almost immediately. We are unsure why there is a settling time in the first place. Even after the settling time the R820T2 had better reception and SNR as shown in the comparison image below. Both dongles were set to the second highest gain setting. R820T2vR820T_BAM At 15 MHz international broadcast AM can be clearly heard with Oliver’s drivers. The R820T2 gets clear reception with a very low gain setting, whilst the R820T can obtain similar SNR with a higher gain setting. Though with a higher gain setting used on the R820T more noise seems to appear as can be seen in the comparison image below. R820T2vsR820T_14MHz

Low Loss Coax

We also tested the low loss coax cable used in our RTL-SDR Blog branded antenna bases and found that it had approximately 3 dB less loss compared to the standard cable when used at most frequencies above 100 MHz. The test used a 1M length of each coax, with the HackRF as the signal generator. The direct connection test used a straight MCX->SMA Male adapter to directly connect the HackRF and RTL-SDR together. Low_Loss_Coax