Category: SDRplay

SDRplay Updates: RSPdx Now Supported by SDR Console V3, RSPdx EXTIO Released

SDRplay have recently released an update regarding third party software support and availability of their latest RSPdx receiver. They write:

Happy new Year from all of us at SDRplay.

Here’s an update on additional software for the RSPdx. SDRplay’s SDRuno fully supports the RSPdx but it takes several weeks for other software to catch up to the capabilities offered on the other RSP models.

Simon Brown has released his latest version of SDR Console V3 which supports the RSPdx (Version 3.0.18 dated January 1st) over on (make sure you download the latest API 3.x from our downloads page first)

We have released an EXTIO plugin for the RSPdx which will enable the RSPdx to work with any EXTIO-based software (e.g. HDSDR) although it doesn’t support HDR mode. HDR mode will not be added and the source code for the plugin can be found on our GitHub repository ( we will not be supporting the plugin source code or extending the plugins capabilities. They are all free to be modified.

It is important to note that the RSPdx ExtIO plugin does NOT, AND WILL NOT, support HDR mode. If you need HDR mode, then SDRuno is the best option. HDR mode requires the end application to work in a certain way and this is not something that can be controlled via the ExtIO protocol.

Work has also begun on supporting RSPdx for SoapySDR based applications such as Cubic SDR (again this won’t include HDR mode). A Gnu Radio source block for the RSPdx will follow.

We are working with Steve Andrew, author of the Software Analyser software programme (see ) to help get compatibility for the RSPdx – this is a slightly longer process so this will take several more weeks.

Regarding stocks of the RSPs, SDRplay and most of our resellers on have plenty of stock of RSP1A and the RSPduo. However there continues to be a shortage of the RSPdx whereby many of the resellers have sold out of their first deliveries. SDRplay is queuing up their replacement orders on a first come, first served basis. We also have our own quantity planned in there to allow us to sell direct from our website. We still hope that by the end of January we will have supplied this second wave of RSPdx demand.

The RSPdx
The RSPdx

Mike from SDRplay Compares the RSPdx Against Other SDRs on MW/LW

Over on the SWLing post blog we've seen a post contributed by Mike Ladd who works with SDRplay. Mike has been comparing the new SDRplay RSPdx on medium wave and long wave reception against the Elad FDM-S2, Airspy HF+ Discovery and the Perseus. The RSPdx is SDRplay's latest product which sits at the top of their line as their highest performance single tuner receiver.

Each test consists of a video where he runs a comparison between the RSPdx and another receiver. All SDRs are run in SDRuno, the official application for SDRplay receivers. It is left for the listener to determine which SDR sounds better. From a listeners perspective, it appears that the RSPdx performs at least identically to the other SDRs.

Comparing the RSPdx Against other SDRs
Comparing the RSPdx Against other SDRs

Testing the SDRplay RSPdx in HDR Mode on NDB and Broadcast AM DX

One of the selling points of the recently released SDRplay RSPdx is it's special High Dynamic Range (HDR) mode which can be used to improve signal performance for frequencies below 2 MHz. This mode should be especially useful in RF environments where there are strong signals that can overload the SDR and desensitize reception on weaker stations.

Over on YouTube Ivan (aka icholakov) has uploaded a video showing comparisons of signals being received with HDR mode turned on and off. He tests it on weak NDB DX signals, and on medium wave broadcast AM. The results do appear to show that using HDR mode results in an improvement in signal strength.

SDRPlay RSPdx HDR mode on and off - testing Non Directional Beacons and Medium Wave

Decoding Differential GPS (DGPS) with an RSPdx and MultiPSK

Over on YouTube the TechMinds channel has uploaded a new video about decoding Differential GPS (DGPS) using an SDRplay RSPdx SDR. DGPS is a terrestrially transmitted long wave signal that is used to help correct and improve GPS position data calculations which may have timing errors due to atmospheric propagation delays. It works by broadcasting correction data calculated by the difference in received GPS location and the known location of the DGPS transmission site. DGPS is typically transmitted on longwave between 285 kHz and 315 kHz, but in Argentina there are two stations at 2570 and 2950 kHz.

In the video TechMinds explains how DGPS works, and some location around the world from where it is transmitted from. Later in the video he shows a DGPS signal being received by a SDRplay RSPdx SDR, and then show a demo of how it can be decoded with MultiPSK.

We note that there also various other DGPS decoders available including decoders for Android and iOS. A list of decoders can be found on the DGPS sigidwiki page.

DGPS Differential GPS Decoding With RSPdx And MultiPSK

The SWLing Post Reviews the SDRplay RSPdx

Thomas from the SWLing blog has been playing around with the recently announced SDRplay RSPdx and has come out with a comprehensive review of the unit. In the review he also provides some comparison videos on real signals between the RSPdx and other SDRs like the WinRadio Excalibur, and Airspy HF+ Discovery.

In the review Thomas notes that while having the advantage of being a wideband receiver, the predecessor to the SDRplay RSPdx (the SDRplay RSP2) was never able to compete with the similarly priced Airspy HF+ and Airspy HF+ Discovery units when it came to HF, MW and LW receiving performance.

But now with it's 0 to 2 MHz enhanced HDR mode activated, Thomas notes that the new RSPdx is majorly improved over the RSP2 in terms of sensitivity and selectivity on the medium wave bands. Thomas' tests also show substantial improvements in the shortwave bands.

The SDRplay RSPdx
The SDRplay RSPdx

Comparing Four Wideband Magnetic Loop Antennas on HF with an SDRplay RSPduo

Over on YouTube the Scanner and Sdr Radio channel has uploaded a video comparing four different brands of HF wideband loop antennas using an SDRplay RSPduo. The loops he tested include the cheap Chinese MLA-30 (~$40), the Cross Country Wireless (CCW) loop ($70), Bonito ML200 (~$442) and the Wellbrook 1530LN (~$305).

The MLA-30 was slightly modified with the cheap coax removed and a BNC connector added. Each of the antennas used a wire loop with diameter of approximately 1.6m, except for the Wellbrook which has a fixed size solid loop of 1m.

The tests compare each loop against the Wellbrook which is used as the reference antenna. In each test he checks each HF band with real signals on the RSPduo and compares SNR between the two antennas.

The results show that the two expensive antennas, the Bonito and Wellbrook, do generally perform the best with the lowest noise floors, but surprisingly the MLA-30 actually performs very well for it's price point, even outperforming the Wellbrook reference on SNR in some bands. We note that some of the improvement may be due to the larger 1.6m loop size used on the MLA-30, compared to the 1m loop on the Wellbrook.

Also we note that it can be hard to compare antennas in single tests, because the differences in antenna radiation patterns could be favorable for some signals, and less so for others, depending on the location.

Comparing 4 magnetic loops for hf

First YouTube Reviews of the SDRplay RSPdx

SDRplay recently released news about their upcoming RSPdx software defined radio, which replaces the RSP2 as the top of the line unit in the SDRplay lineup. The RSPdx is not yet on sale, but a few YouTube reviewers have already received their units. The first review comes from Mile Kokotov who is known to have reviewed several SDRs in the past. Mile's impressions are that the receiver works very well. He writes on his video blurb:

Today i have received the new SDR receiver from SDRplay, the RSPdx and was eager to turn it on and do some tests receiving on HF and VLF. Although at the moment my mini-whip antenna is not operational, I have connected some 20 meters wire as an antenna and start listening on VLF, LW, MW and HF...

I have to say that SDRplay team did a good job with this SDR-receiver, putting better filters and redesigning front-end to improve dynamic range and enhance overall performance in relation to its predecessors RSP2 and RSP2pro. The new RSPdx is very good indeed. Especially on HF and below.

The RSPdx has new features like HDR (High Dynamic range) mode for reception within selected bands below 2 MHz. HDR mode delivers improved intermodulation performance and less spurious responses for those challenging bands.

The New SDRplay RSPdx receiver - First Impression: Excellent!

The second review is by SevenFortyOne who runs through the various features of the SDRplay and also tests it on various HF signals.

SDRplay RSPdx Overview and SDRuno V1.33 Demo

The third video isn't exactly a review, but here TechMinds shows us how to run the RSPdx as a panadapter on his FTDX-3000.

FTDX-3000 Panadapter Setup With SDRPlay RSPdx

Running an RTL-SDR On up to 100 Meters of USB Ethernet Extension Cable

Over on Aliexpress and eBay there are now multiple USB2.0 extenders that work using Ethernet cable. These extenders advertise that is is possible to use up to 100m of Ethernet cable. Extending the USB connection rather than using coax cable is desirable as coax cable introduces signal losses the longer it is. Extending the digital side of the SDR (the USB cable) results in no signal being lost.

However, the USB2.0 specification notes that the maximum limit of the length of an extension cable is only 5 meters. We can go beyond 5 meters by using active repeater cables, but even this has limits of up to 30 meters maximum only.

So how can these USB2.0 Ethernet extenders advertise a length of up to 100m? These devices essentially convert the USB signal into an Ethernet network signal. Ethernet cable for network connections has a limit of 100 meters. Using this Ethernet extender is quite similar to using a Raspberry Pi and running the RTL_TCP software over an Ethernet cable, except that the network connection is handled entirely by the hardware.

We purchased a $45 USB2.0 extender from Aliexpress to test (there is also a cheaper $32 unit that we saw recently that should work too). The extender comes with a 1.5m USB Male to Male cable, a transmit box, a receive box and a 5V plug pack. The transmit side plugs into the PC via the USB Male to Male cable. The receiver end is placed up to 100m away, and this side must be powered by the 5V plug pack. In between you can run up to 100m of Ethernet CAT cabling.

USB2.0 Ethernet Extender from Aliexpress
USB2.0 Ethernet Extender from Aliexpress

In our testing we purchased a 50m CAT6 cable and tested to see if the extender would work with an RTL-SDR Blog V3, Airspy and SDRplay. Initially we had trouble getting SDR# to connect to the RTL-SDR. Eventually we found out that the provided USB Male to Male cable provided was of poor quality. After replacing it with a higher quality cable the extender began working properly. We also found that some USB ports on our PC wouldn't run the unit. The USB3.0 ports on the back of the PC connected directly to the motherboard worked best.

USB2.0 Ethernet Extender
USB2.0 Ethernet Extender Test

Using SDR# the RTL-SDR Blog V3 worked exactly like it was connected directly to the PC. There was no lag noticed at all, with tuning being instant. Sample rates up to 3.2 MSPS worked fine, although of course 2.56 MSPS was the limit without drops. As the receiver box is powered by a 5V plug pack, there was plenty of power available to power a 100 mA LNA via the V3's bias tee as well.

Reliability was a bit of an issue. Sometimes we'd need to replug the USB port several times before it would connect to the RTL-SDR. But once running everything appeared to be stable, and we left it running overnight at 2.56 MSPS without any problems.

Unfortunately the lower bit rate and sample rate of the RTL-SDR appears to be the limit of what the extender can handle. The Airspy with it's higher data transfer requirements due to it's 12-bit ADC didn't work properly, with audio stuttering from dropped packets (even at the lower 3 MSPS sample rate with packing enabled). The SDRplay also wouldn't work, with the SDRUno software being unable to detect the RSP1A. Even using a shorter 2M Ethernet cable did not help for these SDRs. In theory it should work since Ethernet can support a much higher data rate, but perhaps the converter chipset used in the cheap extender unit that we have isn't fast enough.

If you want to try this out, be very careful of what you purchase on Aliexpress/eBay/Amazon. There are some very very cheap USB to Ethernet extenders out there that are advertised as USB2.0, but not all of them are truly USB2.0. The very cheap ones under $5 won't work. Those cheap units actually degrade USB2.0 down to USB1.1 which will not work for an RTL-SDR or any other common SDR. The extender units that will probably work properly are all priced over $30.

It's also possible that some of the more expensive units available on Amazon (e.g. [1][2][3]) may be implemented better and might work with the Airspy and SDRplay. If you've tried one of the pricier units please let us know in the comments if it works. In particular this $156 KVM unit which claims a high data rate and also supports PoE may work (although PoE may cause switching noise). For extreme extensions of up to 250m, USB2.0 fiber optic extenders such as this $359 unit, or this $459 fiber optic unit which can go up to 5km (3.1 miles) might also work. If you've tried any of these please let us know in the comments.