Friday, May 31, 2019

SDRs - Does the Enclosure Matter?

Traditional receivers, and most SDRs, have been encased in aluminium. Conventional wisdom says this is because they need to be protected from RFI. In later years though, some of the SDRPlay SDRs have had plastic enclosures, and the new Airspy HF+ Discovery is also said to be encased in plastic. It's been said that the RSP1A enclosure has an inner metal paint. That could be, but it looks like plastic, and it feels like plastic.

Anyway - aluminium enclosures are offered as a third-party solution to those who prefer metal, and I ordered one. When it arrived, I naturally had to remove the plastic enclosure, so I thought why not test the device with real signals, and without signals, in its original enclosure, the new metal enclosure, and bare? Just to find out how efficient they would be.

So I ran tests on FM and SW with 8 MHz bandwidths and compared spectra and waterfalls in SDR Console.

The results were...interesting. As a matter of fact, there was no difference whatsoever, even when the RSP1A board lay bare on the floor.

So, is conventional wisdom wrong? Not necessarily, my test is circumstantial evidence only. That said, my radio room has four PCs running, 5-6 SDRs and even a couple of rather dirty switching PSUs. So, lots of potential RFI. But the RSP1A was as immune bare as it was enclosed.

I'll keep the metal enclosure though, it's a bit smaller than the original plastic one, and looks much better. And there are other hazards to electrical equipment than RFI. Especially when they're on the floor!

Saturday, May 11, 2019

Some Candidates for the MW SDR DX-er

I’ve been a MW DX-er since my teens. Any other part of the radio spectrum is mostly tuned casually. Hence, I tend to evaluate my SDRs only by their MW performance.

A dedicated MW DX-er has some prerequisites for his or her receivers:
  • Sensitive enough to pull in signals in a low signal level environment.
  •  Robust enough to not overload easily when signal levels are high.
  • Access to software which can record and play back the entire MW band as efficiently as possible.

With the SDR being a “software defined radio”, it is true that software does define the radio experience. Software for the MW DX-er is worth a study of its own. However, at this stage, I thought it might be interesting to have a look at hardware that I have either tested myself, or that I think I know enough about to evaluate for MW DX-ing.

I even thought out a rather complex system for ranking the SDRs since they come in a large variety of price and performance levels. But the system relied on too many subjective factors, so for the time I settled for making an “Editor’s Choice” at the end of this article.

Software supplied with the hardware are listed in bold. Only Windows software versions are listed. Links to the SDR's home page and review pages where available.

RFSpace CloudIQ

9 kHz-56 MHz. Ethernet. External 5V, 0.5A. Max sampling rate: 1807 kHz (1500 kHz tuning range), good for MW. Sensitivity -111 dBm. Good front end. Two antenna ports, software switchable. USD 630. Out of stock – discontinued? Available as used but scarce. Software: Spectravue, SDR Console. Receiver link. Eham review.
RFSpace NetSDR

0-32 MHz. Ethernet. External 5V, 1.3A. Max sampling rate: 2 MHz (1600 kHz tuning range), good for MW. Sensitivity -102 dBm. VHF/UHF add-on board optional. USD 1450 in 2011. Discontinued, available as used but scarce.  Quite large footprint. Software: Spectravue, SDR Console. Receiver link.
Expert Electronics ColibriNANO

0-55 MHz. USB. USB power (USB 2.0 is ok). Max sampling rate: 3 MHz, 1536 kHz (1230 kHz tuning range) is good for MW. Sensitivity -90 dBm, noise floor is on the high side. EUR 300. Available. Smallest SDR. Software: ExpertSDR2 (no IQ file playback!), HDSDR. Receiver link.
Microtelecom Perseus

0-40 MHz, USB. External 5V, 0.75A. Max sampling rate 2 MHz (1600 kHz tuning range) is good for MW. Sensitivity -103dBm. Good front end. EUR 800 in 2019, few available. Discontinued? Available as used but scarce. Software: Perseus, HDSDR, SDR Console, Jaguar Pro/Jaguar Lite. Receiver link. Eham review.
Elad FDM-S2

9 kHz-52 MHz + FM and 135-160 MHz. USB. External 5V, 750 mA. Max sampling rate 6144 kHz, 1536 kHz-option (1230 kHz tuning range) is good for MW. Sensitivity -106dBm. EUR 525, available. Software: FDM-SW2, SDR Console. HDSDR. Receiver link. Eham review.
Winradio G31DDC

9 kHz-50 MHz. USB. External 12V power. Max sampling rate 2000 kHz, 1600 kHz tuning range is good for MW. Sensitivity -106dBm. Robust front end. GBP 700, available. Software: Winradio (IQ recordings will not store/display date and time! No IQ recording scheduler!), HDSDR (current dll only supports bandwidth up to 1000 kHz, 800 kHz tuning range). Receiver link. Eham review.
Winradio G33DDC

9 kHz-50 MHz. USB. External 12V power. Max sampling rate 6000 kHz, 1666.7 kHz sample rate gives a 1250 kHz tuning range which is good for MW, but 32-bit sampling gives double-sized IQ files compared to other SDRs. Sensitivity -110dBm. Very robust front end. GBP 1600, available. Software: Winradio, more options than the G31DDC software, HDSDR. Receiver link.

1 kHz-2 GHz. USB. USB power, 180 mA. Max sampling rate 10 MHz, 1536 kHz option (1230 kHz tuning range) is good for MW. Sensitivity -101dBm but drops off on LW. 2 MHz lowpass filter gives reasonable front end. DAB notch filter. USD 109, available. Software: SDRUno, HDSDR, SDR Console. Receiver link. Eham review.
(NEW! NOV-1-2019)

1 kHz-2 GHz. USB. USB power, 190 mA. Max sampling rate 10 MHz, 1536 kHz option (1230 kHz tuning range) is good for MW, also 600, 300 and 200 kHz spans useful for LW. Sensitivity similar to the RSP1A on MW, far better on LW. Three antenna ports, BNC port for DC to 200 MHz. 2 MHz and 500 kHz lowpass filters give good front end. DAB notch filter. USD 200. Available. Software: SDRUno, HDSDR, SDR Console (coming). Receiver info
Afedri SDR-Net

100 kHz-35 MHz. Ethernet (USB possible but too narrow IQ bandwidth). External 5V power, 370 mA. Max 2500 kHz sampling rate, 1333 kHz tuning range option is good for MW. Sensitivity -104dBm (overloads if gain is set too high), reasonable front end when gain is set low, otherwise poor. USD 260. Available. Software: HDSDR, SDR Console, various others. Receiver link.  Eham review.
SDRs not sampling the full MW band
Airspy HF+/ 
HF+ Discovery
9 kHz-31 MHz + 60-260 MHz. USB. USB power, less than 0.5A (USB 2.0 port is ok). Max tuning range is 660 kHz. Sensitivity -112dBm. Very robust front end. USD 200/170, available. Software: SDR#, HDSDR, SDR Console. Receiver link. Eham review.
Seeed KiwiSDR

10 kHz-30 MHz. Ethernet. External 5V, 1.2A. No IQ sampling. Up to 8 simultaneous channels. Sensitivity -102dBm. Good front end. Can be set up as server. USD 300, less during Massdrop campaigns. Available. Software: None. Runs on any HTML-5 browser, like Chrome, Edge, Firefox, Safari. Receiver link.
SDRs not reviewed
Early Elad and RFSpace SDRs. SDRs with upconverters. SDRPlay SDRs lacking a 2 MHz low pass filter. Any SDR over USD/EUR/GBP 2000. SDRs typically unavailable. SDRs with no, or limited MW coverage.
In the pipeline
Not much, as per May 2019:
Elad FDM-S3 seems to be in its final stage before launch. EUR 950. Two software-selectable antenna ports.
RFSpace CloudSDR – ETA at Q4/18 has been changed to Q4/19. USD 900? Will we see it?

My Picks:

Low price range/entry level: The SDRPlay RSPdx. It is quite sensitive on MW and LW, and may require some attenuation if the signal level is very high. 2 MHz  and 500 kHz low pass filter will help. Several software options. Can double as a sensitive FM and DAB receiver with 6-8 MHz effective bandwidth, depending on PC capacity. All for only USD 200. If your budget is lower, go for the SDRPlay RSP1A (USD 109).

Middle price range: Microtelecom Perseus. It is sensitive on MW and LW, good dynamic range and several third-party options including the bespoke Jaguar Pro/Jaguar Lite software which lifts the Perseus to the top of the sky. EUR 800 but limited stock, occasionally shows up on auction sites. A bit fiddly installation procedure. Others: Elad FDM-S2 (available, EUR 525), RFSpace CloudIQ (out of stock, maybe discontinued, USD 630). The Winradio G31DDC (available, GBP 700) will be a very good alternative if it gets full HDSDR support.

High price range: Winradio G33DDC. Very sensitive, and very good dynamic range. But a hefty price for the performance (GBP 1600), and limited software options which some may like and some will not. Others: RFSpace NetSDR, only available on the used market (USD 1450 new). Good sensitivity and dynamic range, several software options.

If IQ recording of the entire MW band is not important, consider the ethernet based KiwiSDR. No IQ recordings, but up to 8 simultaneous channels (USD 300). Audio recordings are possible from all channels. Or the USB based Airspy HF+ with excellent sensitivity and dynamic range. Several software options, 660 kHz alias-free IQ recording (USD 200).

But you will likely discover that IQ recording of the entire MW band is important.

Updated October 30, 2019.

Friday, May 10, 2019

A Second Look at the ColibriNANO SDR

I tested this SDR briefly back in 2017. I never got round to measure its sensitivity back then, and I also hoped that the manufacturer had addressed the many software issues I had. So almost two years after, I did another test. The original write-up (see links to the right) has been updated.

Spoiler: No, it's not worth €300.

Friday, May 03, 2019

A New Look at the Winradio G31DDC

I bought the G31DDC when it was brand new, thinking that this would be an excellent competitor to the Perseus SDR. Actually, it was an excellent receiver, installation goes in a breeze and it uses 12VDC external power, which is a lot easier to find in no-noise versions than 5VDC PSUs. Sensitivity is around -105 dBm, a tad better than the Perseus. But there were "issues"...

First, the Winradio GUI. It is, at least in my opinion, by no means optimised for efficient MW DX. And at the time there were no software alternatives. Second, and by far more important, the IQ files it recorded were not date- and timestamped! Absolutely disastrous, if you record a lot. And to top it all, no scheduler was available. What on earth were they thinking? Later, the G33DDC came along, with the recording issues solved, but still the old inefficient interface. And with the price doubled.

So, after a short while, my Winradio adventure ended.

I did notice later on that dynamic link libraries (dlls) were developed for use with HDSDR, but at that time I had parted with my G31 and G33.

Recently, related to a project I'm working on, I decided to take a new look at the G31DDC. So, I borrowed a unit (thanks TJ!) downloaded the HDSDR dll and tested the unit. Lo and behold, it is a good receiver!  The only downside is that the current dll only supports 1000 kHz sampling (800 kHz alias-free). So, the requirements for a good MW performer are still not met. But I believe that the dll could be revised to allow 1600 kHz alias-free sampling.

Because, with HDSDR, time- and datestamped files and scheduling is no problem at all.