SDRplay Release the RSPdx: Replaces the RSP2/pro, Filtering & Intermod Improvements, 1kHz to 2 MHz HDR Mode

The RSPdx
The RSPdx

SDRplay have just released their new SDR that they're calling the RSPdx. This is their new top end product which replaces the older RSP2/pro line. The RSPdx is designed for high performance DX reception and they write that it achieves this with additional filtering, improved intermodulation performance, a DAB notch filter, additional attenuation steps, and a new high dynamic range for frequencies under 2 MHz.

Pricing is £159 GBP or $199 USD (excluding taxes). It doesn't yet appear to be for purchase, but they note that it will be fully released within the next few weeks.

The RSPdx is a replacement for the highly successful RSP2 and RSP2pro SDR receivers, which have been extensively redesigned to provide enhanced performance with additional and improved pre-selection filters, improved intermodulation performance, the addition of a user selectable DAB notch filter and more software selectable attenuation steps .

The RSPdx , when used in conjunction with SDRplay’s own SDRuno software, introduces a special HDR (High Dynamic Range) mode for reception within selected bands below 2MHz. HDR mode delivers improved intermodulation performance and fewer spurious responses for those challenging bands.

The SDRplay RSPdx is a single-tuner wideband full featured 14-bit SDR which covers the entire RF spectrum from 1kHz to 2GHz giving up to 10MHz of spectrum visibility. It contains three antenna ports, two of which use SMA connectors and operate across the full 1 kHz to 2 GHz range and the third uses a BNC connector which operates up to 200MHz.

The RSPdx also features a 24 MHz ‘plug and play’ reference clock input which allows the unit to be synchronised to an external reference clock such as a GPS disciplined oscillator (GPSDO)

This is one of many video guides from SDRplay - makers of the RSP family of SDR radios. See the full list of SDRplay videos and applications documents on:

SDRplay is a UK company. The RSP SDR receivers are made in the UK and can be purchased for worldwide delivery directly from (click on purchase and select your country to view shipping costs) or you can buy from any of our worldwide resellers listed here: Many of the resellers offer local free shipping and/or local language technical support.

SDRplay Product Comparisons
SDRplay Product Comparisons

Mike Ladd (KD2KOG) who works for SDRplay Technical services has provided the following demonstration video.

Major Announcement... The RSPdx from SDRplay.

Independent reviewer TechMinds has also uploaded a new hardware and software overview and unboxing video as well.

NEW: SDRPlay RSPdx 1Khz - 2GHz HDR SDR Receiver


  1. Jim West

    While the SDRPlay RSPdx replaces the SDRPlay RSP2 Pro, I can not find a web site with ahead to head comparison of the performance differences between the RSPdx and the RSP2 Pro. The marketing release for the RSPdx is the typical how great the new product is. I currently own two SDRP RSP2 PRo. Before I buy the RSPdx, I would like to undersetand the performance difference, so I can decide to make the purchase or not. I do not want to buy the RSPdx and then find out later that the performance difference between the RSPdx and RSP2 Pro was not enough to justify buying the RSPdx. Please point me to a good objective discussion of the performance difference between the RSPdx and the RSP2 Pro. I would like to find an objective critical performance comparison not written by SDRPlay or someone being paid by SDRPlay..

  2. ssssssssssdeer

    “the RSPdx will only work with SDRuno running on Windows initially”

    How come this wasn’t mentioned at all? No Linux, no p25, how is this even useful?

    • DH

      Its useful because most of the computing world uses Windows. And note that they said “initially”, which implies that Linux compatibility is in the works……

  3. Lee

    I certainly appreciate the review and most certainly appreciate the discussion and points made in the comments above. I am new to SDR and am (was?) about to buy the RSPdx, but after reading all of the comments and trying to understand the references (remember, I’m new to this), I may widen my search. Thanks to all for your input and frank opinions- they do help.

  4. ksshin

    Just want to mention: the “receiver sensitivity” and the “noise figure” of the boards, published by the manufacturers, assumes the ‘best condition’ (input signals are not strong enough to overload the LNA, and so on ..), and does not necessarily apply to real-world scenarios.

    If you want to know the actual performance of the radios, you will have to actually get them and test them out.

    I don’t know much about the specs of Airspy units and SDRPlay units, but Bill is correct in that knowing the noise figure of the unit is equivalent to knowing the sensitivity of the unit. It just takes a bit of conversion. The question is whether the units actually achieve the claimed performance in real-world scenarios.

  5. Ladislav OK1UNL

    Me checked known schematic diagram of one older RSP receiver. I suppose again one low pass filter for HF and newly any filter for frequency 500kHz and down. it is not too much. Airspy Discovery has a limited frequnecy range, but better filtered.

    • Alan

      The only published schematic that I am aware of was for the original RSP1. Since then SDRPlay has stated that the filtering has changed in all subsequent products, so I do not think that you can claim that this device has inferior filtering to the Airspy Discovery. I don’t think anyone knows at this stage. I have a RSP1, a RSP1a and an Airspy HF+ and the RSP1a was a big step up in performance from the RSP1. I find the HF+ the best performer in the MW AM band, but the difference with the RSP1a is small. That said, I generally use the RSP1a at VHF, UHF and L-Band and the HF+ below 30 MHz. I am interested to hear how this new device compares.

      • Ladislav OK1UNL

        Alan, we do not know total price for RSPdx , but all these “low cost” SDR using Low pass filter for HF only .For example Kiwi project.
        Better filtering requires toroidal ferrite cores, winding and measuring. These operations are “hand made” work.
        of course price rising up. see on Elad, Perseus etc…
        Do not forget another point is a Q parameter of really toroidal inductors versus SMD inductors.
        You have a true, initial RSP1 model was published complete with schematic diagram.
        On another side RSPdx can be good panoramatic adapter for ham radio transceivers.

  6. Robert

    Hi Bill .
    I disagree with you on that and so does Airspy and the military . Airspy posted the receiver sensitivity numbers .
    The military always gives the receiver sensitivity on their radios .

    • Bill

      Well Robert, if by sensitivity you mean Minimum Detectable Signal (which is what Airspy quote), then you can work it out from the NF as you are so smart. Here’s a clue:
      Sensitivity = NF + KTB

      Funny isn’t it, Whenever there is news about Sdrplay, you always get someone jumping in shouting “Airspy, Airspy, AIRSPY!!”


      • Car Seller !

        And ? What is the problem to know wich SDR is the best to receive low signal ? If i use “perseus” you will not make the remark ?
        When you buy a car the manufacturer give u all details … about !
        Either if some manufacturer lies about !
        If i want to buy a new product i expect this new product is better then old one … because in your side if you buy new product worst then older one … this is pretty strange for me !

  7. Robert

    Sorry I am old school noise numbers is just noise to me . Example I am using HDSDR software and Airspy discovery . The noise floor I have is -120 and the RF attenuation -24 db at 20 meters . now if I use Sdrsharp I get a noise floor of – 90 db at -24 db attenuation . So what does the mean , it.s all noise to me . Now if they put out receiver sensitivity numbers that is something I can understand . Airspy put receiver sensitivity out for everybody to see . This way it’s apples to apples , not fruit salad .

    • Bill

      Conducted sensitivity is pretty meaningless at HF and below because the atmospheric noise is almost always a lot higher than the self generated noise of the receiver. So in that regard quoted sensitivity numbers rarely mean anything at all when you are using a real antenna.

    • Anon

      They quote the noise figures, so you can easily work out the MDS as that is simply another representation of receiver noise floor. Noise figure is the more scientifically correct way to represent this as it takes variables such as bandwidth out of the equation.

      • Timmy

        I used the formula here ( ) to convert from Noise Figure (given in the four datasheets) to obtain the MDS so that I could compare them to each other and more importantly to hardware from other vendors.
        But what I see is that either the RSP2/RSP2pro was an amazing piece of hardware or the numbers in the the datasheet smell strongly of bovine faecal matter.

        The info would be mangled if I posted directly here so I put them where they would not be mangled

          • Andrew

            Hi Gary
            Microtelecom specify a MDS of -131 dBm for the Perseus SDR with the internal preamp on as a conducted measurement. Most people recognize the Perseus to be the benchmark when it comes to sub $1k SDRs and I have never heard anyone suggest that it might need an external preamp. The HF+ MDS is specified as -140 dBm, but I really doubt that it is actually 9 dB better than the Perseus for weak signal reception at HF. The key for any HF receiver when it comes to sensitivity is to ensure that the self generated noise of the receiver is comfortably below the atmospheric noise coming from the antenna. To check this, simply disconnect the antenna and if the noise floor actually falls by 6 dB or more, then the self generated noise of the receiver is having negligible impact on the overall sensitivity.
            I don’t have a Perseus or an SDRPLAY, but I do have an HF+ and the one thing that I learned is that HF MDS specs are meaningless without a clear statement of the frequency at which they are measured. Without the infamous R3 modification, my HF+ was as deaf as a post at LF, so it came absolutely nowhere near the claimed -140 dBm MDS.
            Ultimately, I am interested to see how any device (including this new one) actually works in the real world with a real antenna.

            • Gary

              “I really doubt that it is actually 9 dB better than the Perseus for weak signal reception at HF”

              In AMDX, every decibel of sensitivity counts. That’s the main reason why we still use expensive pre-amps and filters with the Perseus. The closest competition so far in the amateur market is the Discovery and I want to believe there is something new in the scene.

              Now there are other considerations like the dynamic range, but I’m not going to beat a dead horse. A third party assessment by SM5BSZ shows a stunning difference of 30 dB between the Perseus and the RSP. SDRPlay do not publish any BDR figures, and I can understand why. More filtering will definitely help with signals far away from the signal of interest, but it can’t make any difference if you are chasing a signal with a co-channel blowtorch. Again, this is the reason why the Perseus is maintaining its pricing after so many years, not because of its NF.

              That said, if you are living in a noisy area or use an inefficient antenna, even the Perseus with an external pre-amp won’t make any difference and no amount of filtering will help you. In such conditions, a mid-range radio will be perfectly fine. My understanding is that the RSPdx is targeting this niche.

              “Ultimately, I am interested to see how any device (including this new one) actually works in the real world with a real antenna.”

              Agreed. I want to see how the 2MHz LPF affects the reception, but I am very skeptical. The total RF power in the MW band is much stronger than what is being filtered out. Is there any break-thru in the mixer, IF or ADC designs that is not documented? Unless I am missing something, I only see extra filters added to the RSP2/pro.

              Back to the sensitivity. To make things in perspective, here’s a list of receivers with their respective sensitivities as compiled by the AMDX community:


              • Bill

                The only RSP that SM5BZ uses for comparative purposes is the original RSP1. This is a 5 year old ($100) design that has been out of production for several years and the later devices have come on a very long way, so whilst his observations are relevant for RSP1 owners, they are meaningless for owners of the later products.

                “That said, if you are living in a noisy area or use an inefficient antenna, even the Perseus with an external pre-amp won’t make any difference and no amount of filtering will help you. In such conditions, a mid-range radio will be perfectly fine. My understanding is that the RSPdx is targeting this niche.”

                This is not how I read this product at all. Sdrplay have clearly stated that this device is a replacement for the RSP2 – which was a general purpose SDR operating up to 2 GHz, with substantially improved performance below 2 MHz. The RSP2 was not specified for operation below 1.5 MHz on the 50 ohm ports, so you really had to use the Hi-Z port, which had NO pre-selection. So in that regard, this device is really more of a competitor to the Airspy R2.

                I had a RSP1 and now have a RSPduo and the comparative performance at MW is like night and day. The RSPduo is actually very good, so I am very keen to see how this new device compares.

                    • radiolistener

                      I suspect RSPdx is yet another receiver on MSi2500, so it’s parameters is limited. Just a new filters/LNA was added, but it won’t help much. You can get the same (or even better) performance with cheap RTLSDRv3 and external filter 🙂

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