Category: News

Low Power RTL-SDR ‘Stratux’ Dongles Now Available in our Store

Over on our store we now have a limited amount of “Low Power V2” RTL-SDR dongles available for sale for $16.95 USD incl. free international shipping. These are dongles that were produced for the Stratux project which aims to provide a very low cost ADS-B and UAT receiver for small airplane pilots. These Stratux kits typically consist of a Raspberry Pi, two nano RTL-SDR dongles, a GPS dongle and a Android or iOS tablet. The two RTL-SDR dongles receive both 1090 MHz ADS-B and 978 MHz UAT which are decoded on the Raspberry Pi. The Raspberry Pi then sends the decoded aircraft position and weather data to the tablet via WiFi which is running commercial navigation software.

A full Stratix setup including, Raspberry Pi, two RTL-SDR nano dongles, GPS module, fan, and 1090 + 978 MHz antennas.
A full Stratux setup including: Raspberry Pi, two RTL-SDR nano dongles, GPS module, fan, and 1090 + 978 MHz antennas.

One issue that Stratux users continually run into, is that the Raspberry Pi is sometimes unable to power two or more RTL-SDR dongles. When running a Pi with two RTL-SDR dongles, a GPS dongle, and cooling fan the total power draw is above 1A which can cause power supply problems and glitching. By using a low power RTL-SDR these problems can be avoided by keeping the total current draw under 1A.

The Low Power V2 Stratux RTL-SDR’s draw about 160-170 mA, whereas standard dongles draw about 260 mA, so that’s a saving of almost 100 mA. On battery power this current saving can mean a few hours more of operation. The Low Power RTL-SDR dongle achieves its lower current consumption by using a switch mode power supply instead of a linear regulator which is commonly used on most other RTL-SDR dongles. The trade off is that switch mode supplies are inherently RF noisy, so increased noise can be seen on the spectrum. Despite the increased noise, most applications like ADS-B are not significantly degraded. We have seen switch mode supplies used on some other RTL2832U dongles sold in the HDTV market as well. For example all the R828D based DVB-T2 dongles that we have seen use switch mode supplies as well, and also draw about 170 mA.

We think that these low power RTL-SDRs could be useful in other non-stratux related applications too. For example, they could be used on mobile Android devices. One of the key problems with Android usage is that RTL-SDR dongles tend to drain the battery quickly. They could also be used on solar and battery powered installations to help achieve longer run times. Or like with Stratux they could be used on a Raspberry Pi running other applications, to ensure that multiple dongles can be attached.

Currently we are selling these dongles for $16.95 USD with free international shipping included. Note that these dongles do not come with an enclosure (just a bare PCB), and they do not have a TCXO. Below is more information about these dongles.

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The Stratux Low Power V2 Dongle.
The Stratux Low Power V2 Dongle

Back in November 2016 we posted a review on the Low Power V1 dongles. Since then Chris (the man behind producing these dongles) has brought out the Low Power V2 models which improves upon V1 significantly. By switching to a 4-layer PCB the dongle is now much quieter in terms of RF noise produced from the switch mode power supply, and it also now runs significantly cooler. The dongle also now uses even less power and is more sensitive compared with V1.

Over on his Reddit post Chris compared his Low Power V2 dongle against the Low Power V1, a generic nano dongle and a NESDR Nano 2. In terms of noise plots, the generic nano dongle was the quietest, with the low power V2 dongle coming in second. Interestingly the NESDR Nano 2 was almost as noisy as the low power V1 dongle. The improvements on the low power V2 dongle make it usable on VHF now.

Noise Floor Comparisons between four Nano styled dongles.
Noise Floor Comparisons between four Nano styled dongles. NESDR Nano 2 (Blue), Generic Nano (Orange), Low Power V1 (Gray), Low Power V2 (Yellow).

In terms of heat produced and power used, the NESDR Nano 2 is the hottest and most power hungry, followed by the Generic Nano, the Low Power V1 and then the Low Power V2. For comparison the NESDR Nano 2 draws 1.362W of power, the generic nano 1.318W, the Low Power V1 1.003W, and the new Low Power V2 draws only 0.933W.

Thermal Camera Photos of  four Nano Dongles.
Thermal Camera Photos of four Nano Dongles.

Chris summarizes his results as follows:

  1. The NESDR Nano 2 loses in pretty much every aspect except for noise floor on VHF frequencies compared against the Low Power v1.
  2. You can see the effects of heat on the R820T2 above 1.4 GHz.
  3. The “Generic Nano” was always a great performer in terms of sensitivity.
  4. For ~0.8W (in a dual-band build) less power, the cost is 0.41 dB @ 1090 MHz and 0.64 dB @ 978 MHz (compared to the Generic Nano).

The Low Power V2 dongles appear to be a good improvement over the V1 models. They are useful for applications that need low power draw, for example powering multiple dongles on a Raspberry Pi and for use on battery and solar power. The trade off for low power consumption is increased RF noise, but with the Low Power V2 dongles the noise is not significant and interestingly even outperforms the NESDR Nano 2.

LimeNET SDR Based Wireless Networks Crowdfunding Campaign

Following the success of the LimeSDR, the Lime team have started work on their next SDR project called ‘LimeNET’ which will eventually be released for crowdfunding on CrowdSupply. To be notified when the campaign is released you can sign up here.

The LimeNET SDR is essentially a high-end computer combined together with a LimeSDR board, and all placed in a small box. The goal is to create self contained base stations for cellular and IoT applications. LimeNET devices come in two flavors, the LimeNET Mini and the standard LimeNET.

LimeNET Mini

A software defined radio (SDR) small cell network in a box for mobile and IoT applications, based on an Intel i7 processor and the open source LimeSDR board. This combination makes it an ideal implementation for high data rate communication applications such as to 2-5G radio access to IoT nodes and much more.

  • Processor: Intel Core i7-7500U CPU 2-core 2.7/3.5 GHz
  • Memory: 32 GB DDR4 2133 MHz
  • Storage: 512 GB SSD
  • Connectivity: 1 x USB 3.1 type C, 1 x USB 3.1, 2x USB 3.0, 1 x Gigabit Ethernet
  • Radio: LimeSDR USB Type-A


A software defined radio (SDR) high capacity network in a box for mobile and IoT applications, based on an Intel i7 processor and the open source LimeSDR PCIe card. It covers the same applications as the mini version for wide area networks.

  • Processor: Intel Core i7-6950X CPU 10-core 2011-3 140 W 3.0 GHz 25 MB Cache
  • Memory: 64 GB DDR4 2133 MHz
  • Storage: 1 TB SSD
  • Connectivity: 2 x USB 3.1, 4 x USB 3.0, 1 x Gigabit Ethernet
  • Radio: LimeSDR PCIe
The LimeNET Mini.
The LimeNET Mini.

The LimeNET press release reads:

Confronted with flat revenues, spiralling infrastructure costs and massively escalating data demands, the telco industry is facing a crisis point. It needs exponentially more cost-effective solutions, as well as new revenue streams, and needs to find them quickly. Operators face a simple choice; either revise their business models, or lose market share to new incumbents.

Lime Micro and Canonical are looking to turn the mobile telephony business model on its head. Telco hardware is expensive, slow to develop, and has proven a ‘break’ to innovation in the industry. By ‘open sourcing’ Lime Microsystems’ 5G and IoT capable SDR base station design, Lime and Canonical are looking to effectively ‘commoditise’ network hardware and shift the value centre towards software.

LimeSDR-based base stations can not only run cellular standards from 2G or 5G, as well as IoT protocols like LoRa, Sigfox, NB-IoT, LTE-M, Weightless and others but any type of wireless protocol. Open source base stations allow R&D departments to try out new ideas around industrial IoT, content broadcasting and many more. Commoditised base stations allow any enterprise to run their own base station and get spectrum from their operators as a service. Base stations can have new form factors as well, like being embedded into vending machines or attached to drones.

“It’s clear that existing telco business models are quickly running out of steam,” commented Maarten Ectors, VP IoT, Next-Gen Networks & Edge Cloud, Canonical, “and that operators need to find new revenue streams. Together with Lime Microsystems, we’re looking to initiate a ‘herding’ behaviour that will usher in the age of the largely software-enabled telco network. Through its open sourced SDR design Lime will encourage a wide range of manufacturers to produce more cost-effective base stations. And, following enormous interest in our first crowdfunding initiative, we already have the critical mass of developers required to deliver the significant software innovation the industry requires.”

“This kind of model is, without a doubt, where the industry needs to go,” commented Ebrahim Bushehri, CEO, Lime Microsystems. “There are several reasons why Canonical’s heavy commitment in this project over the past couple of years has been so important. For one, Canonical shares our vision of an entirely software-enabled future for telco and IoT networks. Secondly, Canonical’s efficient, hyper-secure IoT OS Ubuntu Core is the perfect platform to enable this vision. Thirdly, this collaboration has helped us to gather the critical mass of developers required to kick-start the programme.”

Over 3,600 developers are currently involved in efforts to create apps, called Snaps, for LimeSDR, with several free and paid-for apps having already appeared on the open community LimeSDR App Store, as well as Lime’s invite-only app store, LimeNET.

SpyServer 2.0 Released: More Efficient Streaming for Airspy and RTL-SDR

Back in March the team behind the Airspy SDR and SDRSharp software released the SpyServer, a piece of software that allows you to stream radio data from a remote Airspy receiver over a network. Then later in April they added full support for the RTL-SDR dongle as well.

This Easter the Airspy team have released SpyServer 2.0, which improves the streaming efficiency significantly (changelog). Now the full 8 MHz bandwidth of the Airspy should be easily streamable over an internet connection. With SpyServer 1.0 it was difficult to make use of the full bandwidth of the Airspy because the network data usage was very high, since it was streaming the full raw IQ data for the sampling rate/bandwidth selected. In SpyServer 2.0 the server does not stream the full raw data, and instead only streams the wideband FFT data (for displaying the waterfall and FFT graph), and the raw data from the currently selected IF bandwidth. Of course the full IQ data can still be streamed if desired by selecting the ‘Use full IQ’ checkbox.

This new efficiency means that WFM uses only about 1.3 MB/s, and narrow band modes like NFM/AM/SSB only use about 120 kB/s of network data which is easily achievable over a local network and internet. This data usage is almost independent of the sampling rate/bandwidth selected so you can stream the full 8 MHz offered by the Airspy without trouble. Normally streaming the full raw data for 8 MHz would use about 40 MB/s, which is difficult to achieve over a local network, and impossible over the internet.

We tested the new SpyServer over our local network and were able to stream the full 8 MHz of the Airspy with no problems. With the RTL-SDR we were also able to stream 2.4 MHz without issue. WFM and NFM modes worked clearly and no skips or significant lag was noticed over a local WiFi N connection. Hopefully in the future SpyServer will be developed further to enable compressed audio streaming as well for even lower network data usage.

SpyServer WFM Reception. About 1.3 MB/s network usage.
SpyServer WFM Reception. About 1.3 MB/s network usage.
SpyServer NFM Reception. About 120 kB/s network usage.
SpyServer NFM Reception. About 120 kB/s network usage.

Some Operational Notes:

  • To run SpyServer on Windows simply double click on spyserver.exe. On Linux extract “spyserver_linux_x86” and the config file, and then run “sudo chmod +x spyserver_linux_x86”. Then run it with “./spyserver_linux_x86”.
  • Connect to it on the remote PC in SDR# using the servers IP address which can be found by typing “ipconfig /all” in Windows command prompt, or “ifconfig” on Linux.
  • To select between using the Airspy and RTL-SDR for the SpyServer you will need to edit the spyserver.config file with a text editor and edit the “device_type” string.
  • SpyServer runs on Windows/Linux as well as small embedded computers such as Raspberry Pi’s and Odroids. Download the Raspberry Pi and Odroid servers separately from SDR# at
  • SpyServer is NOT compatible with software that expects an rtl_tcp server such as SDRTouch.

We have also seen Lucas Teske of the OpenSatellite project use the SpyServer for streaming a GOES16 downlink over a network connection with an Odroid C2. He writes that soon the OpenSatellite project software will directly support SpyServer.

Titus II SDR Updates

Over on the blog we’ve seen news of an update regarding the PantronX Titus II SDR. The last update we had was in January. contributor Richard Langley writes:

There was a segment on the latest episode of AWR’s Wavescan (9 April 2017) about the Titus II DRM receiver recorded during the recent HFCC meeting in Jordan. In it, it was stated that the shipment of the first 1500 units was expected at the end of March or by the first half of April. Included some discussion of added shielding to prevent digital noise and the high-sensitivity of the receiver compared to other DRM units. 

Head over to the post to listen to the Wavescan podcast announcement,

The Titus II is an Android Tablet + SDR combination that is due to be released in the near future. Its main purpose is for reception of Digital Radio Mondiale (DRM) which is a digital broadcasting medium used on the HF frequencies, which somewhat replaces standard short wave AM radio. The Titus II hopes to be one of the first low cost receiver solutions for this market and as a wideband SDR it should work for many other applications too. From the advertised frequency range of 100 kHz – 2 GHz we speculate that it will be using the Mirics SDR chipset, which is the same chipset as used in the SDRplay. The target price is under $100 USD.

The Titus II Portable SDR
The Titus II Portable SDR

A Warning for R820T2 RTL-SDR Purchases on eBay/Aliexpress etc

Just a brief warning for those purchasing the generic dongles on eBay and Aliexpress. We’ve recently heard of a number of customers having ordered generic dongles advertised as having R820T or R820T2 chips, but receiving dongles with FC0012 chips inside instead.

The R820T2 is capable of tuning from around 24 MHz to 1766 MHz, whereas the FC0012 can only tune between 22 – 948 MHz. Compared, the R820T2 is definitely the better chip.

This scam is probably happening because the price of the FC0012 is less than the R820T/2. So these sellers may be trying to cut costs and simply hoping that no one will notice the chip change since both chips are RTL-SDR compatible in the drivers. You can check what tuner chip you have either with rtl_test, or simply by reading the markings on the chip itself.

In addition we have also recently seen several scammer bots on eBay pop up who are selling our own RTL-SDR Blog V3 dongles at very low prices. These sellers are typically automated bots that mass copy popular listings, and undercut their price hoping to grab a few fake sales before disappearing. They usually have zero feedback, or a small amount of feedback from purchases made from the account, and they price the product extremely low, typically even below the manufacturing cost. Most likely you will never see a product from them and they will simply disappear from eBay after a few days. This has already happened to one scam seller that we have been tracking, although before they disappeared they had already made 80+ fake sales.

FlightAware Prostick Plus Now Available in our Store

The FlightAware ProStick Plus is an modified RTL-SDR designed specifically for ADS-B reception. Its main defining feature is that it has a built in low noise figure LNA, and a 1090 MHz SAW filter. The LNA reduces the noise figure of the RTL-SDR, improving ADS-B reception and thus increasing the number of messages received and the receivable range of aircraft. The SAW filter helps remove out of band signals which can cause the RTL-SDR to overload if they are particularly strong. The Prostick Plus also comes with a TCXO, and SMA connector.

If you are mainly interested in ADS-B reception, or are looking to set up an ADS-B station then the Prostick Plus is one of the best choices you can make. See our previous review here.

We are now reselling some of FlightAware’s Prostick Plus dongles in our store now. They cost $24.95 USD including free shipping worldwide. We intend to sell them mainly to customers outside of the USA, as FlightAware already sell them officially on Amazon, but we offer free shipping anywhere in the world.

Click here to visit our store

The Pro Stick Plus RTL-SDR based ADS-B Receiver from FlightAware.
The Pro Stick Plus RTL-SDR based ADS-B Receiver from FlightAware.

The FreeSRP SDR is now Seeking Crowd Funding on CrowdSupply

Back in August of 2016 we posted about Lukas Lao Beyer’s work in creating a software defined radio from scratch. His goal was to design something that fit somewhere in between the $300 HackRF and the higher end and more pricey USRP radios. Back then he had completed the design and had a working prototype.

Now the Lukas has put the FreeSRP up on CrowdSupply, a crowd funding website. The FreeSRP is priced at $420 each and the goal is to raise $75,000 in order to begin a manufacturing run of the SDR.  At the time of writing this post, the campaign has been running for a day at is already 8% funded.

The FreeSRP has a tuning range from 70 MHz to 6 GHz, uses a 12-bit ADC with a sampling rate of up to 61.44 MSPS, and has a maximum analog filter bandwidth of 56 MHz. It is a full-duplex radio (can transmit & receive at the same time). The main chip in the unit is the fairly expensive (~$150 USD) AD9364 integrated RF transceiver chip and it also comes with a Xilinx Artix 7 FPGA. Furthermore the hardware and code is entirely open source.

The specs seem somewhat similar to the cheaper LimeSDR, although the main chipset is different as the FreeSRP uses the AD9364 chip and the LimeSDR uses their own LimeMicro LMS7002M chip. The AD9364 is the same chip used in the USRP B200 units. Below is an in-class comparison given on the FreeSRP CrowdSupply page.

FreeSRP Comparisons and PCB Image
FreeSRP Comparisons and PCB Image

Below is the FreeSRP promotional video.

KiwiSDR Massdrop: $50 Saving on the Retail Price

The KiwiSDR is a wideband HF software defined radio that is designed to receive the entire 10 kHz – 30 MHz spectrum all at once. It works together with a BeagleBone single board computer and uploads it’s wideband radio data to the internet via the OpenWebRX SDR web interface and control software. Examples of KiwiSDRs shared publicly on the web with OpenWebRX can be found at

Back in April of last year the KiwiSDR was successfully crowd funded on Kickstarter, and was later released for general ordering in October from SeeedStudio. Normally the KiwiSDR kit including KiwiSDR, BeagleBone, enclsoure, GPS antenna and SD card costs $299 USD.

Currently a Massdrop is underway for KiwiSDR (it seems that the link only works for logged in users). If you didn’t already know, a Massdrop is an organized group buy effort. Buy grouping several individual orders together and making a bulk order, the manufacturer is likely to give a discount. Currently the price for the KiwiSDR kit on the Massdrop is $249.99 USD ($50 saving on the regular price), with only 2 days remaining to join in. Once finished, the estimated shipping date is April 24, 2017.

The KiwiSDR
The KiwiSDR