Sunday, 17 December 2017

Ode to SDRplay RSP2

Unadulterated and highly personal review follows of a product I love. Been writing this post for many months, in fact, over a year, adding and subtracting, cracking an RSP2 is not possible, like an onion, deep into the rabbit hole, then some.
Conclusion: get Visa or Mastercard out, be happy. RSP2 is the beginning, the end, the ultimate Software Defined Radio.

Got my RSP2 before 2016 Christmas as a review sample, been using since as often as I could.
Normally, I do reviews with lots of images as a rule, but rules are to be broken, and this is not a review. Do a review of your wife when cooking, who cares when the end result is a nice dinner?
SDRplay introduced their first receiver, now called RSP1, nearly two years ago. Good receive performance, combined with all-in-one form factor, and integration with one of the best front-end software made it a popular choice.
Two years is a long time for a software defined radio (SDR), therefore a facelift was in order.
Price had to remain below 200 dollars and the new product, unsurprisingly called RSP2, had to work with existing software, so the core remained the same 12-bit tuner. Pretty much everything else has changed: most of the shortcomings I mentioned in my previous review has been improved, then SDRplay added more features. Then more.
Then head of finance showed up, inquiring how SDRplay will make a profit on the RSP2, was tied to a chair and made to listen to "All I Want for Christmas" whilst engineers went back to work:
- Improved case with RF screening,
- Three antenna ports, one with bias-T, one dedicated for sub-30 MHz,
- FM and MW filters,
- software-adjustable low noise amplifier,
- clock synchronisation,
- and so on, read the official Data Sheet here.
If you don't know what any or all of the above means, be rest assured that the RSP2 is one of the latest, most technologically advanced, and most practical Software Defined Radio receiver.
SDRplay sent a production unit RSP2 for testing shortly after the official announcement - thank you. As always, what you read here is my honest opinion.
I'd like to make one thing crystal clear before we start: this is not a lab review. I don't live in a lab. has already done one and featured the RSP2 several times, therefore I listened to the RSP1 and the RSP2, alongside the best the RTL-SDR scene and traditional solutions has to offer, in two countries at multiple locations, at sea and on land, with various antennas for over a year.
Written down what I heard at the field and at home, then interspersed notes with comparative technical details and personal observations.
Again, do not read what follows if you value your time, if thinking of buying one and need justification, stop thinking, buy one if you can afford it

Pricing and availability

Less than, or close to 200 dollars' equivalent local currency, depending on where you live. To Ireland, an RSP2 delivered costs a few bobs below 200 euros. That's birthday and Christmas put together money range.
200 dollars seems a large wad of cash for a small plastic box if you're unfamiliar with radio equipment prices: a handheld communications receiver, or a top portable world-band radio costs about the same.

Who is it for

- people thinking of upgrading from RTL-SDR based dongles,
- existing RSP1 users,
- newbies with a gold credit card wanting a one-time purchase,
- amateur radio ops looking into SDRs and yearning for a good solution.


Plastic box with printed instructions inside envelope, protective red caps on SMA ports. Slightly larger than a pack of cigarettes, small and light enough to put into a pocket, won't pull your pants down.

New case material and texture, RSP1's coffee stirrer plastic quality is gone, replaced by a textured matte black finish. Feels in the hand like an industrial handheld transceiver, better than a Baofeng, equals an Icom, still not Motorola level, but a huge improvement over the RSP1.
Minor changes on the case, antenna ports moved up, so reassembly is easier, two new MCX female ports for clock in and out - these are NOT antenna ports.
Indentation on top, slightly heavier, external changes help distinguishing it from RSP1 in the dark by feel alone.


Comes with own and free native software, called SDRuno, offical link here, which also works with RTL-SDR dongles, so you can familiarize yourself if you got an ordinary dongle, or read my guide by clicking on this link.
A lot of visual real estate will be required to enjoy a maximum of 10 MHz visible span on screen. 10,000 kHz worth of instantaneous spectrum monitoring is cool, but you'll need more than a small laptop screen to actually identify a transmission. Multiple screens, as large, with as much resolution as financially possible is required to fully enjoy 10.66 MSPS.
SDRuno (officially) supports multiple 4K displays and rescaling is click-and-pull, so if you've just robbed a bank, or won the lottery, you can enjoy breathtaking resolution on three 4K LCD TVs.
I only got an old laptop which costs around $400 new, and it managed to spread 10 MSPS across two car boot sale monitors, but with a lot of fan noise. Peace and quiet returned at 5 MSPS, which is more than enough for my purposes.

No antennas nor accessories

Great as a doorstop, albeit a quite expensive one.
Please, send at least a rudimentary coax and any kind of antenna, the general public needs a solution right out from the box to hear signals.


A.k.a sending power down the coax cable to power an antenna-mounted preamp. As explained earlier, LNAs are good for you, not only to overcome coax loss, but to lower overall system noise figure.
RSP2 worked with LNA4ALL, novakx5 LNA, and Outernet's preamp straight away.

Built-in adjustable gain Low Noise Amplifier

Software-selectable, as in there's a button you click in SDRuno, and LNA turns on for selected antenna port.

Three antenna ports

Finally. By my estimate, 100% of enthusiasts use more than one antenna, and screwing on a frequency-specific antenna was a chore with the RSP1. Not anymore: I can keep the discone on Antenna port A for "let's browse around", power a mast-mounted LNA for airband (substitute with 2m / 70cm / whatever you fancy), and use a random wire for shortwave.
A step in the right direction, but not enough. Instead of, or in addition to clock in and out ports, I'd love to see two or three more antenna ports. 

Intermittent personal observation

RSP2 is demanding for an enthusiast. I ride motorbikes, and know my goaround moped gets me there, but by now, I realised the RSP2 is a purebred superbike. Antennas matter a lot, just like throttle control, for weak signals, the difference between a random wire and band-specific dipole was huge in an electrically quiet environment.
In a city, a T2FD is hard to beat, and the RSP shined with it. A 200-horsepower machine needs warm weather, slick tyres and a good rider for fast lap times, just like the RSP2 needs middle of nowhere, a frequency-specific antenna and familiarity with SDRuno.
Make no mistake, RSP2 does the job with a makeshift antenna, riding straight on a highway is easy. SMA connector takes center conductor from coax, so I could get really good performance during a recent plane-spotting session when I left the mag mount at home.
Turn left for the twisty bits and depths of last-degree performance is there to explore.

HF port

Green yoke supplied with RSP2, officially called I have no clue, neither my electrician trade shop when I showed them what I want, couldn't get a replacement. This plugs into the side of RSP2, meant for sub-30 MHz signals.

Update 22/12/2017: search for "5.08mm 3 Way PCB Mount Screw Terminal Block", 10 dollars plus shipping:

Indebted to commenter Ross Bennett, that's what community is all about :-) Many thanks again.

TCXO: Entered frequency will be tuned frequency, hasn't been an issue with RSP1, but SDRplay added the feature anyway.


That means how well a receiver can receive signals. The RSP2 is very sensitive.
Very sensitive. I write this down again, because if you're used to lesser equipment, you will just stare, shaking your head in disbelief. Feel free to read eHam reviews (4.7 out of 5 stars) or Ham Radio Science's post.
Writing about comparative performance versus this or that is moot, as reception is down to 1) antenna, then 2) location, and those two variables will not be the same between readers. Whenever I need to listen to a signal I just reach for the RSP2.

An enjoyable personal journey

I soldered my first receiver with my Dad when I was 6. Three decades later, the RSP2 gives a push. A push to perfect antennas, a shove in the right direction to optimise noise reduction in my home, a mental kick to drive bumpy roads to a hilltop with less man-made noise to catch a signal. Or just for the fun of it, and that, my dear reader, is the biggest feature of this black box.
SDRplay RSP2 is the devil on your shoulder. Whispering in your ear, take me out of a city, give me a good antenna, travel with me to the end of the world, and I will golden the very moment when you and me be at the right place at the right time.

At sea

Took the RSP2 for a spin on the West coast of Ireland during a recent mobilisation, had no issues. X-band and S-band radar didn't seem to affect performance, telescopic antenna with SMA worked well, shortwave was easy with a piece of wire. Couldn't do more due to 6 on 6 off watches, RSP2 worked without a hiccup, wasn't affected by violent vessel movement, unlike I was.

FM filtering

Works nicely. Push a button, FM band wiped out, interference gone.
Easy, as it should be.

Shortwave listening

The RSP2 with SDRuno is a shortwave listener's wishlist coming true.
I had a Tecsun PL-680 along (please refrain from indulging in the portable vs SDR debate for a moment), which is highly recommended by and costs the same.
Audio quality was nowhere near what I could get with the RSP2, the two receivers are not even on the same page.

Living with it

Only had the RSP2 for a while, went to remote locations, without electronic noise to assess HF performance, to the top of nearby mountains to see how far I can hear, and the impression remained the same.
Practicality rules. Magnetic mount on top of the car, with airband antenna, wires leading out from back window for HF. I had a v.3 and a SMArt, plus a Ham It Up representing RTL-SDRs, a Tecsun PL-680 demonstrating what a same-price portable worldband radio can do, and me old Icom IC-R5 as backup.
SDRplay RSP2 never left me wanting.

Personal lifersaver

This is the part you won't care about.
Walked down the slope, to the top of a nearby mountain, set up shop with antennas out the car window, laptop and RSP2 on the back seat as I wanted to get spine-shaking rush to the head of hearing a signal, a small joy, something I was looking forward to after 10 years of a progressively deteriorating relationship, loneliness, depression, "I feel so alone", into the sea, crawled out because I had something to look forward to.

 What to do with an old RSP1?

Give it to someone who needs it, like local schools, ham club, or anyone who could use it. SDRplay sent me an RSP1 for testing aeons ago, and Jon agreed to my proposal, so I have an RSP1 for education purposes. Get in touch with SDRPlay if you live in Ireland, but please only do so if you'll use it for the common good.
This approach is one more reason to choose SDRplay. Kudos to Jon.

Nice company to deal with

Questions to support got answered quickly (, and SDRplay is working with other front-end software such as SDRConsole. And remember, these are the people who made a previously expensive software available for free to RTL-SDR users, then added full 2.4 MSPS support.

Versus RTL-SDRs

To assemble something similar, you'd need:
- dongle with TCXO for $25, 
- one more dongles to get two more antenna ports, add $25 each,
- upconverter for $50,
- preamp for $25,
- adapters to connect all above together, $10,
- FM filter for $15,
- and so on.
More money at the end of the day, just like any consumer product in parts costs an arm and both kidneys at the till if you want to go cheapskate and save money.
Regular readers know that I love RTL-SDRs, but had to grudgingly admit that the RSP1 was a hyperspace jump, and the RSP2 with added features is, despite the seemingly high price, is a realistic alternative if you want and can use its features.
For strong local signals, an RTL-SDR dongle will get the job done for significantly less.
For weak signals, the RSP2 is better than any RTL-SDR based setup.
Mindset matters, like when I was 17, in a testosterone-induced stupor spent my savings on an air filter, bigger rims and the customary ironing board on the back. Piece by piece, and yes, cleaning and detailed polishing will make any car faster.
Fact is, I must admit with a diminishingly balder head, that extra oomph comes from displacement, and this is the point when I have mention the 12-bit nature of any SDRPlay, if you still follow.
Common RTL-SDR dongles are 8-bit, and 12-bit is more, just like a Corvette is more than a Camry.

Versus AirSpy platform

I don't know. I don't have an AirSpy, because I didn't invest in one, despite reviews praising excellent performance, for the following reasons:
1. Software.
2. Two boxes.
3. Costs more.
SDRplays are just one box, which does it all on an old laptop. With HF port on the RSP2, I need an USB cable, a telescopic antenna and a length of wire to get signals locally and from around the globe. Anywhere.
The AirSpy vs SDRplay war raging online is akin to tea or coffee, or whether you should mix chocolate into porridge or just sprinkle on top argument.
Pathetic, really, as both are great receivers, both are excellent value for money - come on guys, let the other camp flourish.
Be merry that we got choices.

Before you buy one

I'd strongly suggest to order a premium dongle (Nooelec SMArt or v.3 or SMArTee XTR bundle) kit for the supplied antennas, and think of dongle as a bonus. Connectors and antennas are compatible and well worth the price alone, receivers are great.
An USB to USB-B cable will be also necessary, try to get one with ferrites on both ends.


The SDRplay RSP2 is the best affordable all-in-one software defined radio receiver.
I can't think of a better solution if you have $200.
RTL-SDR dongles are near, traditional portables have no chance. When you add factors together, the RSP2 always comes out a winner. If you had to pay a thousand dollars, the RSP2 would still win.
More antenna ports: at least four for VHF and UHF and four for HF. I'd love to select frequency-specific antennas for a job with one click. Speaking of, I want editable names for ports in SDRuno, so I can know which port is the discone and which one is the airband.
I want to order green adapters, so I could set up band-specific antennas for mobile operation, a ferrited data cable should be compulsory, and if a company can make a receiver, why I can't order antennas to go with it?
Nothing beats the RSP2 for value for money. Or personal growth. Or what's out there. This little small box offers so much more than words can convey, therefore I can only come to one conclusion after more than a year's use: buy as many as you can afford.


  1. Those little green adapters are "5.08mm 3 Way PCB Mount Screw Terminal Blocks." The 5.08mm bit is significant as it differentiates from another size, but the different sizes are color coded mostly. I just bought twenty pair for $10 for two-day shipping on Amazon. Could have had them for about $4.50 if I'd wanted to wait two weeks for mail order from China.