Cheap "MSI SDR" (SDRPlay RSP1) clones, anybody have one? - Page 1
Forum section: electronics / rf-microwave

author: cdev
author_rank: Super Contributor
timestamp: July 26, 2020, 08:04:37 pm
content: Showing how out of the loop I am I have only just noticed that there seem to be a bunch of cheap "MSI SDR" dongles out now selling for around $40. They are supposed to be compatible with software that works with the SDRPlay SDRs - basically a 12 bit SDR with range from LF to around 2 GHz. Which is fairly respectable, definitely a huge step up from the RTLSDRs. The price makes it quite attractive from my perspective.Does anybody own one?Unlike the original SDRplays they seem to have a 0.5 ppm TCXO - Software support now seems quite good, all the usual suspects make hooks that speak to it. I am worried abour image rejection and performance in a noisy RF environment without the need for band stop filters.I am pretty sure the original SDRPlay has an issue with FM overload, which isnt surprising given how many strong signals are around.

author: radiolistener
author_rank: Super Contributor
timestamp: July 26, 2020, 10:16:54 pm
content: reception quality of MSi receiver is much worse than RTLSDR, but MSi receiver has 9 MHz bandwidth mode.Regarding to Chinese MSi.SDR, it has no filters on the input. Also it has a lot of spurs and annoying crackle sounds on some frequencies. It may be due to fake or defective MSi chips or bad PCB layout. For 145 MHz it has much worse reception sensitivity than RTLSDRv3. Also MSi.SDR has a lot of frequency gaps.In short, if you want better reception quality, less spurs and less frequency gaps and less bugs, then RTLSDRv3 is much better choice.The only MSi.SDR interesting feature is 9 MHz bandwidth mode. For all other things RTLSDRv3 is absolute winner in comparison with MSi.SDR.

author: cdev
author_rank: Super Contributor
timestamp: July 26, 2020, 10:25:02 pm
content: The SDR chip from MSI has multiple internal (digital) filters but the receiver attempts to cover such a wide bandwidth that even if they were traditional analog filters they would have a hard time preventing spurii..But your criticism seems likely to be true. So, compared to the SDRplay, its crap? Or are these problems inherent to SDRPlay also?I have milked the most performace out of my 8 bit RTLSDR that it is possible to get. Its impossible to do much better without more bits.145 MHz (lower part of two meters) is particularly problematic on the RTLSDR for me too. 144 MHz is even worse.

author: radiolistener
author_rank: Super Contributor
timestamp: July 26, 2020, 10:46:11 pm
content: Quote from: cdev on July 26, 2020, 10:25:02 pmI don't have SDRPlay, so I cannot say if these problems are present in SDRPlay or not. According to other users SDRPlay don't have some spur issues, which is present in MSi.SDR. So some difference between MSi.SDR and SDRPlay is definitely present.Quote from: cdev on July 26, 2020, 10:25:02 pmRTLSDR ADC works as expected, but MSi.SDR works a little different and strange, it can handle a little higher signal level on the input with no overload, but with higher noise floor. MSi.SDR has the same SNR or even worse. I suspect that MSi.SDR may use 8 bit ADC with dynamic attenuator which is enabled when input level is too high.Quote from: cdev on July 26, 2020, 10:25:02 pmNo. I'm talking about problems with 145 MHz on MSi.SDR.I cannot hear weak stations on 145 MHz with MSi.SDR.RTLSDRv3 can hear it with no problem...On short wave both have the same sensitivity and works almost the same. MSi.SDR don't have some mirror channels across 14 MHz which is present on RTLSDR. But MSi.SDR has a lot of huge spurs near 30 MHz.I also forgot to say that MSi.SDR has a bit problem with DC offset between I/Q channels. It is so bad, that you cannot remove it even by using wideband DC filter in HDSDR. This issue is masked in SDRuno, because it has always enabled DC filter which cannot be disabled. But in HDSDR you can disable DC filter and see how it really bad.RTLSDRv3 has smaller DC offset and it can be easily removed with IIR filter with just 1 Hz bandwidth. But for MSi.SDR you cannot remove it even with 25-100 Hz IIR filter.Another issue present in my MSi.SDR is sound crackle pulses across entire bandwidth. It's frequency depends on LO frequency. I'm not sure if this is just defective MSi chips or this problem exists on all MSi.SDR devices. But it is very annoying and prevents comfortable radio listening.And another issue with MSi.SDR (at least my one), it works unstable at 10 MHz bandwidth.When I switch to 10 MHz BW, noise floor jumps like crazy. So, 10 MHz mode is unusable on MSi.SDR.

author: cdev
author_rank: Super Contributor
timestamp: July 26, 2020, 11:03:42 pm
content: They were probably made with chips that failed quality control which were probably supposed to be trashed but werent.

author: radiolistener
author_rank: Super Contributor
timestamp: July 26, 2020, 11:08:02 pm
content: Quote from: cdev on July 26, 2020, 11:03:42 pmI have the same thoughts. It also may be bad quality clones of MSi chipset.

author: A.Z.
author_rank: Super Contributor
timestamp: July 27, 2020, 07:07:17 am
content: Hello, if you are referring to those "blue dongles" with a dolphin, that is the ones like thishttps://www.rtl-sdr.com/photos-of-the-msi-sdr-dongle-a-new-sdrplay-rsp1-clone/then I own one, and two friends of mine another pair (we ordered them together); the unit is just like the one depicted above, although it hasn't that electrolytic capacitor soldered on the boardas for performances and defects, I must admit that I didn't perform any measurement, all I can say is what came out from using the unit for some months nowFirst of all, the chipset is really the mirics one, that is the same used in SDRplay units, but according to some informations floating on the 'net, the board design detaches from the RSP1 one, even if plugging the dongle it's identified as an RSP1 (not "a"); performance has been quite good on all bands where I tried the unit, and never had audio issues or the like as reported by others here, same goes for the other two units, so my guess is that there may be some defective or badly assembled units around; as for issues, yes, even if it should have frontend filters, the unit suffers from overloading, I had a bunch of out-of-band interferences generating ghost signals which I was able to pinpoint to a nearby (about 30Km) FM tower, at that point I went on and bought aNooElec "FlaminGo" FM bandstop filterand that solved the issue, other than that, even if it has a metal box, the unit needs good grounding to avoid noise and also choking at both the coax and the USB cables, as for the latter, the one which comes with the unit is quite crappy and it would be a good idea picking a better USB cable (possibly with chokes); in my case I'm using the unit with a random wire antenna fed using aNooElec 9:1 unun/balun V1(the V1 can be configured either way by cutting a trace on the PCB - seehere) and around 25m of RG-58, it has been serving me pretty well for these months and I believe it's definitely worth its price, just give it a decent antenna (the whip shipped with some units is worth nothing) and I believe it will serve you well

author: radiolistener
author_rank: Super Contributor
timestamp: July 27, 2020, 10:37:48 am
content: A.Z., could you please perform some tests with your one?1) Leave input open2) Start HDSDR (with SDRPlay ExtIO plugin). I'm using HDSDR, because it allows you to configure more parameters manually3) Open ExtIO setup and select the following settings (Zero IF, 8 MHz bandwidth, Sample Rate 8MHz, IF gain=45):4) Set LO = 500'000 Hz and take the picture of spectrum, please share it here. Do you hear some low frequency pulse sound hum (about 50 Hz)? I'm interesting if your device has parasitic spurs the same as my one. See my result in attachment5) Set LO = 6'000'001 Hz and Tune = 6'400'000 Hz, do you hear crackle sound pulses with frequency about 3-5 Hz? This is the same issue with pulses.

author: A.Z.
author_rank: Super Contributor
timestamp: July 27, 2020, 02:35:49 pm
content: Will try, but I've to admit that I'm using the dongle using the SDRuno software and not through the extIO, so I'll probably have to fiddle a bit with my system and install some more stuff... so, well, I'll try but don't hold your breath!Also, those "spurs" (vertical lines evenly spaced) WERE present in my unit, until I didn't connect the unit to a good ground and improved the antenna counterpoise and choking system, after that the "lines" (almost) disappeared; also, and since we're at it, here's the unit I bought (although back then the cost was lower)https://www.amazon.com/KKmoon-Broadband-10KHz-2GHz-Panadapter-Compatible/dp/B07YYFJ94Nnot sure if it does any difference, but the above is working ok for me; I reused the pigtail cable which comes with the unit to connect it to the NooElec FM filter (added chokes to the pigtail !) which in turns goes to the antenna coax feedline (chokes there as well, both on the SDR and the antenna side)

author: A.Z.
author_rank: Super Contributor
timestamp: July 28, 2020, 07:09:22 am
content: Didn't yet find the time to run the requested tests (to tell the truth, hadn't time to play with the SDR at all), but given the interest in those MSi.SDR dongles, I thought that people here may be interested in some more details about those chips and their implementations, so here are some links which will offer some more detailshttps://www.rtl-sdr.com/forum/viewtopic.php?t=31http://blog.palosaari.fi/2013/08/mirics-msi3101-sdr-linux-driver.htmlhttp://blog.palosaari.fi/2013/10/naked-hardware-13-logitec-ldt-1s310uj.htmlI hope that the above infos could be helpful and clear some confusion about the mirics chipsets architecture and design choices

author: radiolistener
author_rank: Super Contributor
timestamp: July 28, 2020, 02:12:26 pm
content: HDSDR:http://www.hdsdr.de/It needs ExtIO driver in order to communicate with MSi.SDR:https://www.sdrplay.com/software/SDRplay_ExtIO_Installer_1.2.exeHere is also both together (I didn't tested this version):https://www.sdrplay.com/software/SDRplay_HDSDR_Installer_2.76a.exeQuote from: A.Z. on July 27, 2020, 02:35:49 pmit is impossible to remove these spurs with any kind of antenna, because the source is inside MSi.SDR device and it always present. You can put strong signal on the input to hide these spurs. But if you want to receive weak radio, these spurs and noises will be an obstacle.This is why I'm prefer to use RTLSDRv3 which is twice cheaper and provide much better reception quality (more clean, less spurs, less noise and less distortions)

author: A.Z.
author_rank: Super Contributor
timestamp: July 28, 2020, 04:00:43 pm
content: Quote from: radiolistener on July 28, 2020, 02:12:26 pmAll I can say (at least util I'll find time to run the test - thanks for the links), is that by connecting the MSi.SDR dongle SMA connector gnd to a good ground those spurs totally disappear from the spectrum, then ok, in general you will also want to choke the USB and possibly run over batteries to remove switching PSU noise, but that's a different issue and has nothing to do with the SDR, then if you prefer the RTL unit, that's fine with me, it's just an SDR not a religion or whatever elseall I can say is that I owned an RTL unit and I liked it, but I like the MSi one more, but again that's just me

author: cdev
author_rank: Super Contributor
timestamp: July 28, 2020, 04:31:59 pm
content: All SDRs have certain issues. They do need a good ground. Just about any unun also will help a lot with a long wire antenna.For HF you should try a different receiver than an RTLSDR if you can. Adding additional bits gives you substantial improvements in dynamic range.Make a unun if you have a lot of spurs. You can use any small toroid or ferrite core. Even a ferrite split bead for noise reduction will do great. If you have two identical split beads that makes a really good unun. Use it like you would any binocular core. . Twist the wires you use together to make a bifilar or trifilar winding. This will take five minutes and give you much less noise.Certain kinds of sound card SDRs based on the "Soft Rock" design are easy to build.

author: radiolistener
author_rank: Super Contributor
timestamp: July 28, 2020, 05:27:07 pm
content: Quote from: A.Z. on July 28, 2020, 04:00:43 pmNo, it don't disappears. It always present. Their source is inside MSi.SDR device, so it doesn't depends on grounding or antenna type. It is present with any type of antenna, with any type of ground and with any type of power supply. This is an issue of device, not environment.Quote from: A.Z. on July 28, 2020, 04:00:43 pmthe source of these noises is not USB and not PSU. The source is MSi.SDR itself.I tried to power MSi.SDR from external very clean ultra-low noise linear PSU. Also I tried to add ferrite filters on USB cable. The result - I don't see any visible difference. These spurs are still present independently. It doesn't matters how good power supply and how low is interference from PC. Because the noise source is receiver istelf.At the same time RTLSDRv3 works good on the same USB port and don't have such spur and noise issues.Also I tried to connect MSi.SDR to RTLSDRv3 and can see a lot of parasitic emission from MSi.SDR on it's input connector.Here is example - RTLSDRv3 SMA connected to MSi.SDR SMA connector. So, on the left side you can see parasite emission of MSi.SDR (it is received by RTLSDRv3). And on the right side you can see parasite emission of RTLSDRv3 (it is received by MSi.SDR).These spurs are not processing issue. These are real parasite RF emission from MSi.SDR on it's SMA connector.Also you can see crackle pulses around entire bandwidth of MSi.SDR (green spikes on the waterfall).Also, MSi.SDR has a noise issue from USB transmission, you can catch it in some modes. See the second screenshot for example.

author: radiolistener
author_rank: Super Contributor
timestamp: July 28, 2020, 06:06:42 pm
content: Quote from: cdev on July 28, 2020, 04:31:59 pmThe bits don't tell you all info. Many bits may works much worse than less bits receiver. You're needs to take into account ADC speed, SNR, IMD and other specification for ADC and RF frontend. This is something like compare 5 megapixel professional camera with high quality optics and large matrix and cheap 10 megapixel camera from smartphone with a small and noisy sensor. It has much more megapixels, but works much worseRTLSDR and MSi.SDR are example.RTLSDR has 8 bit ADC working at 28.8 MHz but it has better performance than MSi.SDR which has 12 bit ADC working at 24 MHz.I have DDC receiver on FPGA with fair 14 bitAD6645ADC. So, I can compare it with RTLSDR. RTLSDRv3 works very good for it's price. Yes, it has some mirror channel issues and some spur, it's SNR is about 80 dB. But I'm very skeptic that you can get better performance for less than 100 USD. For comparison, my FPGA setup cost me a little more than 100 USD. Actually I spent more than 200 USD for experiments.Now it can be possible to build setup with FPGA and fair 12 bit AD9226 ADC for about 55 USD + good power supply. It will be much better than RTLSDR or MSi.SDR. But since I already have AD6645, I'm experimenting with 14 bit.Also there is a very interesting receiver on aliexpress:https://www.aliexpress.com/item/4001186751605.htmlI didn't tried it, but it looks very interesting. It uses noisy oscillator, but it can be replaced with ultra-low noise one from Abracon or other known brand.Quote from: cdev on July 28, 2020, 04:31:59 pmunun or antenna cannot fix self noise of receiver. RF choke, baluns and good antenna allows to reduce noise from your home electronic equipment, but it cannot remove noise which is already present in your receiver. It's already here, so you cannot block it.You can put very strong signal on the input to hide receiver self noise, but it still present and when you try to receive weak station you will catch noise of your receiver.

author: A.Z.
author_rank: Super Contributor
timestamp: July 28, 2020, 07:28:46 pm
content: ok folks, if it is a religion war, then I'm giving up, all I can say is that the dongle is serving well, the remainder is just chatter, all the best.andrew

author: radiolistener
author_rank: Super Contributor
timestamp: July 28, 2020, 07:41:45 pm
content: Quote from: A.Z. on July 28, 2020, 07:28:46 pmSorry, but this is not religion war, there is no even a small piece of religion. Just technical talks. I just tell you what issues I found on MSi.SDR.Regarding to spurs and noises, it doesn't depends on receiver type. This is technical fact that self noise of receiver cannot be removed with some magic ground or magic antenna.The goal of RF choke and balun is to prevent common mode currents on the outer braid of coax cable. The goal is to protect your receiver from noises collected by the cable from home equipment. There is no magic and no religion. This is just technical issue.But if noise source is a receiver itself, then there is no way to protect your receiver from these noises, because they are already inside of receiver... So, RF choke, balun and antenna cannot help to remove it.The reason why they are less noticeable with antenna is because your antenna has some strong signal. Since dynamic range is very limited it leads to higher noise floor. Also there are a lot of noise from air. This is why these spurs is less noticeable on the background of real noise from the air.For example, I taken two screenshots. The first one is open input. And the second one is connected antenna. As you can see these spurs are still here, it just becomes less visible in the background of air noise. But these spurs still here with exactly the same level.

author: A.Z.
author_rank: Super Contributor
timestamp: July 28, 2020, 08:14:51 pm
content: again, you aren't getting the point, but it's ok with me, if your custom SDR is doing well, then it's fine with me; that said, maybe I'm crazy, but I won't sell my MSI.SDR for an RTLSDR one, that said, have a nice day.

author: radiolistener
author_rank: Super Contributor
timestamp: July 28, 2020, 08:31:03 pm
content: Quote from: A.Z. on July 28, 2020, 08:14:51 pmI don't propose to sell itJust talking about issues.I have both of them. Also I have different RTLSDR versions.But most of the time I'm using RTLSDRv3, because it has better sensitivity and less self noises, also it don't have frequency gaps. So, when I want to listen some radio, I'm using RTLSDRv3.On the other hand MSi.SDR is useful when you want to see all 8 MHz bandwidth on the spectrum. Because RTLSDR provides max 3.2 MHz.Also there is difference for 14.4-28.8 MHz band. Since RTLSDRv3 use direct sampling for ADC running at 28.8 MHz, it's bandwidth is just 14.4 MHz. All signals above 14.4 MHz will be folded into 0-14.4 MHz (through aliasing). On RTLSDRv3 it's better to use bandpass filter on the input if you want to listen 14.4-28.8 MHz (in order to cut-off broadcast stations from 0-14.4 MHz band). On MSi.SDR there is no such issue (it uses up-conversion inside). But since most of broadcast stations are below 14.4 MHz, this is not a big deal.

author: A.Z.
author_rank: Super Contributor
timestamp: July 28, 2020, 09:00:17 pm
content: all that is fine with me, I do mainly HF bands and MW/LW plus some 79 and 118 MHz (ok around that) listening, and once I properly set up the whole antenna system (including grounding and feedline) I had no issues, plus the better dynamic range of MSi.SDR allowed me to handle conditions which a bare RTLSDR unit wouldn't gracefully handle, again, I'm not pretending it's the best SDR around (I'd be crazy), but for sure it's serving me better than, say, the. nooelec RTL dongle then ... 70% of whatever station (tx too by the way) is the antenna system, but then that's a different topicbest

author: radiolistener
author_rank: Super Contributor
timestamp: July 28, 2020, 10:01:44 pm
content: Quote from: A.Z. on July 28, 2020, 09:00:17 pmHere is comparison for dynamic range left is RTLSDRv3, right is MSi.SDR.RTLSDRv3 is connected through 30 dB attenuator (because RTLSDRv3 has better sensitivity).MSi.SDR is connected directly (with no attenuator).

author: fourfathom
author_rank: Super Contributor
timestamp: July 28, 2020, 10:19:22 pm
content: The SDR-Play has a full set of switchable analog (L/C) filters ahead of the digital sampling stuff. You can find the filter design on the SDR-Play website (https://www.sdrplay.com/wp-content/uploads/2018/01/RSP1A-Technical-Information-R1P1.pdf). The RTLSDR and similar SDRs have much simpler and lower-performance filters so I suspect that the spur performance will be worse.I used the "RTL-SDR Blog V3" in direct-sampling mode for 10 MHz and 7 MHz ham band receivers, and ended up putting an external low/bandpass filter and preamp on it. It worked well enough for my needs, but wasn't nearly as bulletproof as a good ham receiver.

author: cdev
author_rank: Super Contributor
timestamp: July 28, 2020, 10:37:14 pm
content: Quote from: fourfathom on July 28, 2020, 10:19:22 pmThe direct sampling mode on the RTLSDR works particularly well with a tuned magnetic loop antenna. (the kind that is just a loop of wire and a variable capacitor, with a pickup loop)The selectivity of the loop makes up for the lack of selectivity of the RTLSDR. I found that that using that combination was when I got the best performance out of my RTLSDR.Direct sampling it also makes a very good probe for tracking down RFI.

author: radiolistener
author_rank: Super Contributor
timestamp: July 28, 2020, 10:41:39 pm
content: Quote from: fourfathom on July 28, 2020, 10:19:22 pmNo, spur performance don't depends on input filters. It depends on internal circuit LO purity and processing. I think that worse spurious performance of MSi.SDR is due to worse purity of LO NCO. As I mention before, these spurs depends on LO frequency, so I think these problems is due to bad spurious performance of NCO. Probably it uses smaller phase accumulator or something like that.And probably these sound pulses is also due to spurs of NCO. But it also may be caused by mixing of some frequencies used inside of MSi.SDR.I'm interesting if these issues with pulses are present on genuine MSi2500 chip. Because it is possible that MSi.SDR use Chinese clone chips which can have some issues, for example with NCO, which may be missing in genuine chipset.Quote from: fourfathom on July 28, 2020, 10:19:22 pmI suspect that SdrPlay use a lot of filters on the input just because MSi chipset has a big issues with dynamic range or intermod distortions. Because good SDR don't needs a lot of filters. Just proper antialias filter before ADC is good enough.Also I hear that msi001 tuner has just 85dB dynamic range, so this is the reason why MSi.SDR cannot have better dynamic range than RTLSDR. Just because dynamic range of analog frontend of MSi.SDR is limited to 85 dB. So, 12 bit cannot help here, and spurious LO makes things even worse...For example:RTLSDR:8 bit ADC = 6.02 * 8 + 1.76 = 49.92 dBProcessing gain: 28.8 MHz => 3 kHz = 10*log(28800/(3*2)) = 36.8 dBSNR = 49.92 + 36.8 = 86.72 dBMSi.SDR12 bit ADC = 6.02 * 12 + 1.76 = 74 dBProcessing gain: 24 MHz => 3 kHz = 10*log(24000/(3*2)) = 36 dBSNR = 74+36 = 110 dBBut it is limited with msi001 tuner to 85 dB, so the total SNR = 85 dBAlmost the same as RTLSDR...

author: fourfathom
author_rank: Super Contributor
timestamp: July 29, 2020, 12:13:07 am
content: Quote from: radiolistener on July 28, 2020, 10:41:39 pmInput anti-aliasing and preselector filters do indeed affect IMD-related and aliasing spurious responses. But of course so do the A/D and NCO and datapath.

author: radiolistener
author_rank: Super Contributor
timestamp: July 29, 2020, 12:17:50 am
content: Quote from: fourfathom on July 29, 2020, 12:13:07 amI'm talking about self spurs, when there is no signal on the input (open input). They are depends on LO frequency.Regarding to IMD distortion, I tried to measure it, but MSi chipset works very strange. At a glance IMD of MSi chipset is much worse than RTLSDR, but it very depends on the gain, so it's hard to measure it's exact value, because it changes significantly on different gain, signal level and frequency. RTLSDR works more predictable. May be this is because I was used two-tone mix obtained from two square waves, so there is possible mirror channel and aliasing influence.

author: cdev
author_rank: Super Contributor
timestamp: July 29, 2020, 01:31:11 am
content: Quote from: radiolistener on July 28, 2020, 10:41:39 pmNeither the RTLSDR or hackrf has dynamic range much above 60db. Which isnt very good at all. 85 db even would be a huge improvement. 110 db is decent, what I would expect from a decent SDR. A good sound card based SDR can often get that. Its a world of difference.

author: A.Z.
author_rank: Super Contributor
timestamp: July 29, 2020, 07:40:48 am
content: Quote from: radiolistener on July 28, 2020, 10:01:44 pmThank you for the test, as I wrote I didn't run real tests, all I can say is what I experienced; months ago I still had the RTL dongle (the MSi just got delivered), I was listening on the 20m band when a local ham started transmitting there (on a different frequency on the same band), the RTL dongle became totally deaf when that happened; being curious, I switched to the MSi unit and that one was able to deal with the local transmission and allowed me to keep listening the other signals, now I believe this does make a difference, doesn't it ?As for comparing the units, I thought we were discussing about cheap commercial SDR units, and I believe that comparing those with highly priced ones would be like comparing apples and oranges, otherwise we may just compare an RTL or MSi unit with an ETTUS USRP and conclude that the RTL/MSi are crap

author: radiolistener
author_rank: Super Contributor
timestamp: July 29, 2020, 08:25:47 am
content: Quote from: cdev on July 29, 2020, 01:31:11 amI don't have hackrf, so I cannot compare it. But RTLSDR has dynamic range about 80 dB. You can see it on the screenshot.Left is RTLSDR, right is MSi.SDR. There is 40 MHz signal which is shown with -5 dBFS level on both. And both shows noise floor about -85...95 dB.RTLSDR shows SNR = 80 dBMSi.SDR shows SNR = 80-85 dBSome small difference in dynamic rage is really present, it's about 5 dB. But this is almost nothing.Because you can lose these 5 dB on bandpass filter for exampleBut again LO beat and noise which is present on MSi.SDR ruins all advantage.I think it's better to use silent RTLSDR with fair 80 dB, than noisy MSi.SDR with 85 dB and these annoying pulses and buzzing with about 20 dB above noise floor and which you cannot remove.

author: radiolistener
author_rank: Super Contributor
timestamp: July 29, 2020, 08:54:53 am
content: Quote from: A.Z. on July 29, 2020, 07:40:48 amyes, we're talking about cheap SDR with price < 50 USD.Quote from: A.Z. on July 29, 2020, 07:40:48 amMSi.SDR cost about 40-45 USD. This is a lot. By spending just a little more money (about 70 USD) you can build fair 12 bit SDR setup with much better performance.For example:https://www.aliexpress.com/item/4000796488236.html

author: A.Z.
author_rank: Super Contributor
timestamp: July 29, 2020, 10:17:49 am
content: Quote from: radiolistener on July 29, 2020, 08:54:53 amWell, I paid mine around 40 euros, so I believe it's still in the "cheap units" range; as for building ... yes, one can go for that, but then it won't be a "commercial" unit anymoreand then one may decide to look elsewhere and, for example follow this designhttps://circuitsalad.com/2020/01/06/compact-si5351-based-sdr/which also uses a Spin Semiconductors FV-1 chiphttp://www.spinsemi.com/products.html

author: A.Z.
author_rank: Super Contributor
timestamp: July 29, 2020, 12:51:39 pm
content: Just in case, here's mine with the FM bandstop filter and the chokes

author: cdev
author_rank: Super Contributor
timestamp: July 30, 2020, 12:35:05 am
content: With the caveat that it was designed for TV with radio as an afterthought, I am petty sure that the MSI sdr is a 12 bit SDR.The RTLSDR is definitely nothing like a high bit depth SDR. Weak signals cant be heard. This is obvious on the ham bands - any frequency really.That said, the idea of using it for the US digital TV system as well as an SDR is interesting. Can it demodulate TV, say off of the air in an area with broadcast HDTV, either European, Asian ormulti TV systems with an MSI dongle, I wonder?That was what the original literature on it that I have holds out the promise of. (as well as using it as a radio receiver)Also, MSI has a web site. This is all likely explained there.I wonder if one can clock the MSI SDR externally? It would be great if you could clock all your gear using the same GPSDO-derived oscillator signal(s)

author: fourfathom
author_rank: Super Contributor
timestamp: July 30, 2020, 01:17:09 am
content: Quote from: cdev on July 30, 2020, 12:35:05 amI agree that the RTLSDR isn't as good as a higher bit depth one, but in my testing of the RTLSDR-V3 I saw a noise floor of about 0.005 uV. My input was a 10.001 MHz CW signal and I was using the "csdr" program as a SSB demodulator. I set it to 10 MHz, giving a 1 KHz SSB beat-note, and a 5 KHz audio low-pass filter. This was all running on a Raspberry Pi. I used a 10 MHz bandpass filter and a 30 dB preamp at the filter (total gain about 24 dB). With a 1 uV input signal I measured about 55dB SNR. This was using the direct-sampling mode of the RTLSDR.This is pretty decent sensitivity at HF. In fact I may have too much preamp gain, since there will be a tradeoff when it comes to overload. I was more worried about the aliasing though, given the 28.8 MHz sampling clock.If you're curious, here's a ham club presentation I gave on that project (http://wb6cxc.com/wp-content/uploads/2019/04/Presentation-1-0.pdf). Since then I've made a small combo filter/preamp board that I can stuff for any frequency (well into the VHF bands).

author: radiolistener
author_rank: Super Contributor
timestamp: July 30, 2020, 09:37:05 am
content: Quote from: cdev on July 30, 2020, 12:35:05 amNo, they both have the same performance, both use the same technology. And both have SNR about 80 dB. But MSi.SDR has more noise issue, more unstable and has more bugs.As I said before, "bits" is just marketing here. MSi.SDR has performance of usual 8 bit ADC. It may use 12 bit inside, but dynamic range of analog frontend (tuner chip MSi001) is about 70-90 dB (the same as RTLSDR), so you cannot get advantage of 12 bit. At some conditions with MSi.SDR you will get even worse dynamic range than 8 bit ADC.But resolution bits is not the full story. There are a lot of other important things. ADC speed, DC offset, spurious performance, phase noise, LO purity, SNR of RF tuner and many other things. The resolution bits don't play important role in cheap SDR dongle.Quote from: cdev on July 30, 2020, 12:35:05 amThis is false information. RTLSDR has better sensitivity than MSi.SDR.For example, with RTLSDRv3 I can hear very weak signals on 145 MHz. But with MSi.SDR the same weak signals are not detectable at all, I even don't see any indication of carrier presence on the waterfall.In addition, MSi.SDR have much worse dynamic range when you select high gain.Quote from: cdev on July 30, 2020, 12:35:05 amNo. MSi.SDR is Chinese clone. SdrPlay said that MSi.SDR is not their product and they don't support it. They even deleted all messages about problems with MSi.SDR from their forum.Quote from: cdev on July 30, 2020, 12:35:05 amThis is completely useless, both RTLSDRv3 and MSi.SDR use TCXO and frequency error is about 1-2 Hz on 10 MHz. This is almost nothing. There is no frequency drift, just a little frequency error at factory calibration.

author: radiolistener
author_rank: Super Contributor
timestamp: July 30, 2020, 12:01:06 pm
content: Here is my test setup - both RTLSDR and MSi.SDR connected through T connector to antenna. I performed S-level calibration to keep the same signal level on both devices, so you can compare sensitivity level. And the third screenshot with disconnected antenna.It shows receivers in realtime simultaneously.Left part of screen is RTLSDRv3.Right part of screen is MSi.SDR.The first screenshot with connected antenna.The second screenshot with disconnected antenna.Both screenshots taken with the same settings. So, you can compare sensitivity and noise floor.As you can see RTLSDR has a little better noise floor and a little better sensitivity than MSi.SDR.

author: A.Z.
author_rank: Super Contributor
timestamp: July 30, 2020, 12:32:37 pm
content: Since my MSi unit is serving me better (at least in my experience, till now) than the RTL one I had, and since I'm just marginally interested (if it works, I'm just going to try squeezing out as much performance as I can, instead of debating), I'll try to stay away from this, that said, it would be interesting to see what happens to the noise level (at bottom of spectrum display) when you connect the MSi SMA antenna connector ground to agoodground, I'm writing this since in some cases it made a LOT of difference

author: radiolistener
author_rank: Super Contributor
timestamp: July 30, 2020, 12:38:00 pm
content: Quote from: A.Z. on July 30, 2020, 12:32:37 pmI think it's better to understand the root of cause why it serving you better. And I think the root of cause is because when you put very strong signal on the input RTLSDR it is overloaded much earlier than MSi.SDR. Just because RTLSDR has better sensitivity.You can fix it just by adding some attenuator on the input of RTLSDR and you will get the same result.

author: radiolistener
author_rank: Super Contributor
timestamp: July 30, 2020, 12:44:30 pm
content: Quote from: A.Z. on July 30, 2020, 12:32:37 pmIt won't affect result. Both receiver will show you exactly the same result.Because such connections don't affect receiver performance. It affects antenna performance.And I don't recommend you to connect "good ground" it will leads to bad antenna noise performance. The proper way is to use RF chokes on your coax cable and put your antenna and it's counter poise as far as possible from your home and any electric equipment.

author: A.Z.
author_rank: Super Contributor
timestamp: July 30, 2020, 12:48:22 pm
content: Quote from: radiolistener on July 30, 2020, 12:38:00 pmDid that (the attenuator) when I still had the RTL unit, but that didn't solve the issue and in any case didn't help with DX signals (you usually don't want to attenuate them), again, I decided to buy the MSi.SDR dongle time ago, compared it with the RTL I had (same setup), and decided to give away the RTL and keep the MSi, and till now I'm a happy camper, then if it doesn't work for you and you prefer the RTL units, it's fine with me, but I don't think I'll go back to an RTL dongle and then maybe I'll go forward to some better SDR unit (I'm considering the AirSpy HF+ and the RSPduo), but then, it's still just a maybe

author: A.Z.
author_rank: Super Contributor
timestamp: July 30, 2020, 12:49:26 pm
content: Quote from: radiolistener on July 30, 2020, 12:44:30 pmAnd trying that would be easy, so... why not ?

author: radiolistener
author_rank: Super Contributor
timestamp: July 30, 2020, 12:56:05 pm
content: Quote from: A.Z. on July 30, 2020, 12:48:22 pmI believe you, this is not so easy to properly setup and configure all things, it requires to understand a lot of things. This is a common problem when equipment with better performance gives worse results with incorrect settings. I compared both devices very deep and can say that this is almost impossible to get better performance with MSi.SDR instead of RTLSDRv3. With proper setting of course.Of course RTLSDR has it's own cons and pros. For example it suffers from aliasing issue (between 0-14.4 MHz and 14.4-28.8 MHz), you can find these issues on the screenshot that I posted above. But you can fix it with proper LPF/HPF. But overall performance of RTLSDR is much better.

author: radiolistener
author_rank: Super Contributor
timestamp: July 30, 2020, 01:01:06 pm
content: Quote from: A.Z. on July 30, 2020, 12:49:26 pmI prefer to understand what is going on under the hood instead of random trying. I understand what happens and why, when you connect "good ground". Antenna don't needs "good ground", it needs good counterpoise.This is like Ohms law, when you know it, there is no magic why current depends on resistance and voltage. You can predict it and your calculation will be exactly the same when you try to measure it. There is no magic. The same thing is here.When you trying to connect ground, your're change your antenna. Your receiver performance don't depends on the ground, it remains exactly the same. But the ground affects the signal source on the input of your receiver. By connecting and disconnecting ground, you're trying to compare different antennas. Not different receivers.

author: cdev
author_rank: Super Contributor
timestamp: July 30, 2020, 01:10:56 pm
content: You need to use some means of isolating the two receivers from one another. The way you have connected them is not going to be representative of either of them because you will get spurs from one SDR being presented at the input of the other. I would simply use an A/B antenna switch. Thats much better than a splitter because a splitter will give you the same problem, plus attenuation of the signals. Even a cheap CATV antenna switch will work. I would also turn off the SDR you are not using and anything like a upconverter you may be using. Turn off anything that produces LO signals.You do need to use a good ground. Ideally a good RF ground. That is a whole subject in itself. But it is very important. Otherwise your receiver will use its power source and all wires connected to itself. That could bring in a lot of crap. I use a 12 volt battery to power my HF receiver. Doing that right off the bat cleans up a lot of junk. The USB connection brings in its own problems with dirty power. I have always added multiple additional capacitors to the power rails on my RTLSDRs.Also the picture you show, is not showing any way of differentiating the two by dynamic range. You need images that contain more strong signals, next to weak ones. You'll notice that the dynamic range is less than 50 db. Also, the performance of the RTLSDR (the only one of the two I am familiar with) varies a great deal as you move around the bands. Especially on direct sampling. As you mention, the performance at certain bands is very bad, I also find my RTLSDR is almost useless for 10 and 6 meters and VHF low band. Also the bottom of 2 meters which I am very interested in receiving, is horrible.Quote from: radiolistener on July 30, 2020, 12:01:06 pm

author: radiolistener
author_rank: Super Contributor
timestamp: July 30, 2020, 01:13:23 pm
content: Quote from: cdev on July 30, 2020, 01:10:56 pmyes, but I didn't compared spur performance on that screen. I compared sensitivity and noise floor.Such setup is good enough for that goal, because it provides exactly the same signal level for both receiversSignal amplitude is exactly the same on both receiver's input and this is exactly what I wanted for the test.Quote from: cdev on July 30, 2020, 01:10:56 pmYes, this is not dynamic range test. This is sensitivity and noise floor test.Dynamic range of both receivers almost the same. It's about 80 dB.For MSi.SDR if may vary from 45 to 92 dB depends on the gain and frequency.

author: cdev
author_rank: Super Contributor
timestamp: July 30, 2020, 01:21:52 pm
content: I have been unable to receive a bunch of weak shortwave stations using anything on my RTLSDR setup that come in clearly on other more-bit SDRs.That said, for the price, which is very low, they cant be beat.With a good upconverter they compete well with tabletop consumer radios with shortwave capabilities. On direct sampling they can work really well with a mag loop. Which adds preselection.I would be surprised if the SDRplay had only 42 bits of dynamic range. If that was the case I think I would have heard people bitching about it!But it seems to me like you are either accessing some capabilities which I have never seen before or maybe mistaken as far as RTLSDRs having that much dynamic range.Unless they have new drivers that unlock more bits. Which I think is very unlikely. And as I said, HackRF is around the same. What people like about HackRF is the very wide frequency range they support. Not as a high quality solution, as a quick and dirty way of scanning a very wide range of frequencies.Like the RTLSDR, they get you involved by forcing you to spend a lot of time thinking of workarounds so you can get the most performace out of them despite their many shortcomings..After all they were made to sell, as a mass market item, to workers so they could catch a lottle TV on their laptops.Sell profitably for $10.And so, being so cheap, for learning they are ideal.

author: radiolistener
author_rank: Super Contributor
timestamp: July 30, 2020, 01:37:35 pm
content: Quote from: cdev on July 30, 2020, 01:21:52 pmDon't confuse ADC resolution bits, dynamic range and sensitivity. These are different things.If your RTLSDR cannot hear some weak signal while other receiver can do it, it doesn't related with ADC resolution bits. This is just because your other receiver has better sensitivity. Your other receiver may use 5 bit ADC or even 1 bit ADC. It doesn't matter. This is sensitivity issue, not ADC resolution bits.You can use Low Noise Amplifier (LNA) with proper filters in order to listen weak signals on RTLSDR.But regarding to MSi.SDR, it has even worse sensitivity than RTLSDR.Regarding to the bits, you can consider it in complex with ADC speed and analog frontend dynamic range. Because total dynamic range depends on all these things.For example you can get 100 dB dynamic range on 6 bit ADC and 40 dB dynamic range on 12 bit ADC. Just because 6 bit ADC has processing gain and 12 bit ADC has analog frontend and clock phase noise limitations.This is why when you're talking "12 bit ADC" this don't means that it is better than "8 bit ADC". You're needs to consider many other factors.Quote from: cdev on July 30, 2020, 01:21:52 pmI don't agree. Direct sampling on RTLSDRv3 works good enough. And in my opinion it works better than upconverters.The only thing that you can take care is just proper bandpass filter and LNA on the input.But in order to get best performance you're needs to understand how to configure it properly and how to tune it to avoid problems. This is not so easy, especially if you don't know all details how it works under the hood.For example, I never use AGC (automatic gain control) on RTLSDR.For me it's better to setup gain manually, it gives much better result and more control.

author: cdev
author_rank: Super Contributor
timestamp: July 30, 2020, 01:51:49 pm
content: I never use AGC either, and I also have a couple of e4000 RTLSDRs which are much better for UHF than the R820T/T2 SDRs.By all accounts, what the RTLSDRs do, all the many tricks they use to make the most of the bits they have istruly phenomenal.Additionally, on top of that I have done a great many things, to try to stretch their performance even makde a bunch of different LNAs with their front ends optimized (as far as choice of components) for different frequency bands.Still, there are a lot of signals which my RTLSDRs cannot receive, even when put on a good antenna. I would say that as far as the things i want to listen to, most of them are not accessible to an RTLSDR. In the past I didnt have any really good antennas and I had no way of evaluating the ones I made myself, but now I do.Some of it is living in a very noisy RF environment, some of it is also (now) the summer heat. Which raises the noise level substantially in the daytime.But some of it is the radio. I do have a substantially better SDR which I use for HF. And its dramatic. I really do see that on HF.

author: radiolistener
author_rank: Super Contributor
timestamp: July 30, 2020, 01:59:10 pm
content: Quote from: cdev on July 30, 2020, 01:21:52 pmDon't confuse ADC resolution bits and dynamic range. These are different things.And resolution bits is not equals to dynamic range of receiver.SdrPlay use MSi2500 chip it uses 12 bit ADC but it doesn't means that it provide you the better dynamic range, because you're needs to take into account process gain, phase noise, and other things.And the things going even worse, because SdrPlay also use MSi001 tuner chip (the same as MSi.SDR) which dynamic range is limited to about 45-92 dB, depends on the gain settings. It means that you will get just about 80-90 dB dynamic range for receiver. Almost the same as RTLSDR (80 dB).

author: radiolistener
author_rank: Super Contributor
timestamp: July 30, 2020, 02:14:37 pm
content: Quote from: cdev on July 30, 2020, 01:51:49 pmA long time ago I also had the same thoughts that sensitivity and reception quality depends on ADC bits. But when I tried better ADC with higher resolution and higher clock, I found that it don't provide you better sensitivity. It just provide you more dynamic range (it depends on clock speed and resolution bits).Dynamic range just allows you to keep low noise floor with very strong signals on the input. It can be an issue when you have broadcast transmitters near your home. But also you can fix it with bandbass filter.If you want to get better sensitivity, you're needs to work on LNA, bandpass filters. With proper LNA and bandpass filter you can get almost the same result as very expensive top receiver.Better dynamic range just allows you to not use bandpass filters on the input.With RTLSDR and proper filter and LNA you can receive any weak station, if it even possible at allBut if you're want to add LNA, first make sure it has low noise figure. Because noisy amplifier cannot amplify weak signals, it will flood the singal in self noise of amplifier. So, noise figure of amplifier is a critical parameter.

author: A.Z.
author_rank: Super Contributor
timestamp: July 30, 2020, 02:16:00 pm
content: Quote from: radiolistener on July 30, 2020, 01:59:10 pmOk, I'm off from this; someone please, buy one oftheseso that they could be compared to the RTLSDR, I suspect they'll come out just a bit better, but the RTLSDR will still be the winner; oh well

author: radiolistener
author_rank: Super Contributor
timestamp: July 30, 2020, 02:26:58 pm
content: Quote from: A.Z. on July 30, 2020, 02:16:00 pmWhat you're want to achieve from receiver? What is your goal?With RTLSDR and proper LNA and bandpass filter you can get almost the same result as with ETTUS or any other top receiver...It doesn't means that RTLSDR is better. This is very like smartphone photo camera with "just press the button" functionality vs professional photo camera. Professional photo camera allows to do much more quality photo. But it also requires much more knowledge to control it.ADC bits here is the same as megapixels. You can have 10-20 megapixels with cheap optics on smartphone and 5 megapixels on professional photo camera with high-end optics and large matrix. And your 20 megapixels cannot beat 5 megapixels of professional camera with good optics...

author: cdev
author_rank: Super Contributor
timestamp: July 30, 2020, 02:41:36 pm
content: I've been doing that. (building filters and LNAs and various antennas)And its true, for many applications the RTLSDR is "good enough". A few years ago, it would have taken a rack full of hardware to receive 24-1700 MHz in any fashion. Also, the direct sampling, although a bit of work to get going, is an amazing extension of the functionality to lower frequencies the hardware was never supposed to be able to receive.The RTL's low price makes it very compelling. And like perhapseven millions of other people, all around the world, (and that was definitely because they were so affordable) I've learned a lot using them.I'm not challenging their usefulness. I'm just saying that they have their limitations.The analogy you draw between a small image sensor and a larger one is a very good one, and there is no way around it, when you have a 3.1 megapizel camera's most high resolution image, it wont enlarge to be printable over a certain size. If you want to print out a large image and have it not be blurry, you need to invest in better cameras and better lenses.Also, even if you have a great lens, the sensor matters a lot.Similarly with the RTL, They have a lot of birdies (which vary from unit to unit quite a bit) and they can't receive really weak signals. They do inspire a lot of experimentation - to work around all these problems.Which is probably my goal, learning. So in that respect they have been great.

author: radiolistener
author_rank: Super Contributor
timestamp: July 30, 2020, 02:55:34 pm
content: The difference between top end receivers, such as ETTUS and cheap one such as RTLSDR is not ability to listen weak stations. The difference is reception quality - signal distortions, spurious performance. And if we compare MSi.SDR and RTLSDR from this point of view, we will found that MSi.SDR is more cheaper receiver than RTLSDR. But actually MSi.SDR cost twice more than RTLSDR.The only interesting feature of MSi.SDR is just wideband spectrum view, with almost 8 MHz at once on the screen. This is really interesting feature. But this is not receiver feature. This is spectrum view feature. For double price you will get wideband spectrum view, but worse reception quality and a lot of issues. It's up to you to decide whether to double pay for it or not.By the way MSi.SDR has text "Panadapter" instead of receiver. So, Chinese guys don't lie and said truth. MSi.SDR is really good and cool as a panadapter with 8 MHz bandwidth on the screen, but not as receiver.I really like to see all 8 MHz of spectrum on the screen in real time. This is really amazing!But when I want to listen for the radio, I prefer to use my RTLSDRv3

author: radiolistener
author_rank: Super Contributor
timestamp: July 30, 2020, 03:38:02 pm
content: With FPGA and ADC module you can build your own setup and get even better features, for example see attachment for screenshot with entire 24 MHz bandwidth at once in realtime on the screen. This is really amazingI can see almost full short wave bandwidth from 0 Hz till 24 MHz in realtime...On the second screenshot you can see spurious performance of my setup from 0 Hz to 24 MHz. The scale is dBFS (0 dB is the maximum allowed level with no overload = 1.697 Vrms). There is some little DC offset on the ADC input, so it shows about -28 dB on DC.As you can see, noise floor is about -150 dB/Hz or -75 dB for 24 MHz bandwidth.This is correspond with ADC datasheet specification SNR=75 dB.For CW (500 Hz) it means dynamic range SNR = 123 dB.With take into account reference voltage 1.697 Vrms, it correspond to CW MDS sensitivity about -105 dBm or 1.2 uV.As you can see, sensitivity is not so good, but good dynamic rangeBut RTLSDRv3 is a small and don't eat much CPU, so this is where RTLSDR shine. It is very small cheap and allows you to listen almost any frequency. Also RTLSDR has a lot of different software. This is why use of RTLSDR is a piece of cake.

author: radiolistener
author_rank: Super Contributor
timestamp: July 30, 2020, 05:01:14 pm
content: Quote from: cdev on July 30, 2020, 01:10:56 pmHere we areRTLSDRv3 connected to NWT with 10 MHz 0 dBm output through 30 dB attenuator.There is -30 dBm on the RTLSDRv3 input. Vertical scale is reset (0 dB equals to max ADC input).CW bandwidth is 500 Hz. RTLSDR shows noise floor about -89.5 dB within 500 Hz bandwidth on the background of -4 dB carrier.So, the dynamic range for CW mode with 500 Hz bandwidth isSNR = 89.5 - 4 = 85.5 dBAlso we can calculate sensitivity for CW mode 500 Hz:noise floor = -85.5 - 30 = -115.5 dBm = 0.375 uVNow we know, that RTLSDRv3 in CW mode at 10 MHz has:- sensitivity about MDS = -115.5 dBm = 0.37 uV- dynamic range about SNR = 85.5 dB

author: fourfathom
author_rank: Super Contributor
timestamp: July 30, 2020, 05:17:53 pm
content: With the RTLSDR-V3 I saw 70dB SNR (1 KHz demodulated CW tone, 25uV input to preamp, 5KHz audio bandwidth). I hadn't quite hit the SNR limit, so I can easily believe you can get 80db+ with a 500Hz bandwidth.

author: radiolistener
author_rank: Super Contributor
timestamp: July 30, 2020, 05:43:49 pm
content: Quote from: fourfathom on July 30, 2020, 05:17:53 pmThis is very predictable. RTLSDR has 8 bit ADC working at 28.8 MHz.ADC SNR = 8 * 6.02 + 1.76 = 49.92 dB (for 14.4 MHz bandwidth)Processing gain for 14.4 MHz to 500 Hz is 10*log(14400/0.5) = 44.59 dBSo, the theoretical maximum of dynamic range for ideal ADC is:SNR = 49.92 + 44.59 = 94.51 dBSince ADC is not ideal, the dynamic range is a little smaller. I think it's about 89.5 dB, the same as measured noise floor. I cannot put more powerful signal on the input, because my NWT output is a little noisy, so there is needs a little margin to avoid ADC overflow.SNR = 89.5 dB means that the effective ADC resolution of RTLSDR is:ENOB = (89.5 - 44.59 - 1.76)/6.02 = 7.17 bit

author: cdev
author_rank: Super Contributor
timestamp: July 30, 2020, 06:01:03 pm
content: If the rtl-sdr mailing list still exists, this would be a question to ask them. A very long time ago there was a big debate about dynamic range there. In theory I think the maximum dynamic range possible with an 8-bit SDR is around 50 db. That said, its my understanding that some people, notably Leif, SM5BSZ, an expert in such things, managed to eke out a substantial bit more dynamic rangeusing custom modifications of the librtlsdr library (with several different possible modes) which he published.However I dont think his suggestions were ever incorporated into the librtlsdr trunk.I think this debate basically died without ever having been resolved. Similarly, there were other modificatiojns that improved the selectivity which never seemed to be incorportated into the librtlsdr.Please fill in the blanks here with some facts if anybody knoews them. I'll be honest, I lost interest in the issue when it became obvious to me that with the exception I think of the GPIO for antenna power the various interesting mods people were making were not going to get adopted and nobody set up an alternative center for librtlsdr development I could trust. the convenience of using a package manager and easier upgrades and my resistance to running sftware whose origins I was not so certain of unless it was vetted by somebody I trust won out for me.Most poeople seemed to move on to other hardware. Given that so much more of it became available. Can you blame them?That said, I would love to see somebody squeeze out more dynamic range from of an 8 bit SDR..With regard to Mirics, this looks interesting..http://www.sm5bsz.com/linuxdsp/hware/mirisdr/mirisdr.htmThe plot thickens..Also seehttp://www.sm5bsz.com/linuxdsp/hware/rtlsdr/rtlsdr.htmPerhaps this is what you mean?"The data delivered from the rtlsdr is only 8 bit. An ideal 8-bit A/D converter should have a SNR of 50 dB The bandwidth delivered by the rtlsdr is 2 MHz while we measure MDS in a bandwidth of 500 Hz. The bandwidth factor is 4000 and that provides a gain of 36 dB. Note that the dongle reaches the theoritical limit in sensitivity mode at gain settings of 0 to -15 dB. Measurements have to be made with a third signal present because otherwise the A/D converter might give the same value most of the time. With a GAAS FET LNA having the gain required to lift the noise floor by 3 dB in sensitivity mode with 0 dB gain setting and with adequate filtering one can get very good performance with the E4000 dongle. With a 1 MHz wide filter at i.e. 432 MHz one can get a dynamic range near 86 dB with a sensitivity only about 3 dB worse than optimum. By increasing the gain to 15 dB one would then have a sensitivity very close to the theoretical limit at a dynamic range of about 68 dB. Note that LO spurs and reciprocal mixing can be the limiting factors. "Note that both of these web pages are around 8 years old a very long time in technology)What I am saying is that additional tricks may be possible,but hooks would have to be provided and agreed upon to utilize them.

author: fourfathom
author_rank: Super Contributor
timestamp: July 30, 2020, 06:04:49 pm
content: Quote from: radiolistener on July 30, 2020, 05:43:49 pmYes. I'm just saying that my measurements, your measurements, and the theory all support each other.As for sensitivity, unless you have a very low-gain (lossy) antenna, at HF frequencies the atmospheric and other noise is going to be the limiting factor. My measured 0.005 uV noise floor (using a preamp) is far below the atmospheric noise. I am far more concerned about IMD, overload, and aliasing.

author: cdev
author_rank: Super Contributor
timestamp: July 30, 2020, 07:15:23 pm
content: The noise level increases a lot in the summer it seems.Quote from: fourfathom on July 30, 2020, 06:04:49 pmIf one can live with their other various quirks, (more spurs than the Rafael Micro ones) the elonicse4000 dongles have better UHF sensitivity than the others.

author: radiolistener
author_rank: Super Contributor
timestamp: July 30, 2020, 09:45:24 pm
content: Quote from: cdev on July 30, 2020, 06:01:03 pmYes, 8 bit ADC has dynamic range:SNR = 8 * 6.02 + 1.76 = 49.92 dBBut this is for entire bandwidth. RTLSDR ADC running at 28.8 MHz, it means that it has 14.4 MHz bandwidth. So, these 50 dB is for 14.4 MHz bandwidth.But there is no need 14.4 MHz bandwidth to listen CW, AM or SSB. For example SSB needs just 2.7 kHz bandwidth. Due to processing from 14.4 MHz to 2.7 kHz we get additional 10*log(14400/2.7) = 37.2 dB of dynamic range.It means that for SSB mode RTLSDR 8 bit ADC has theoretical maximum of dynamic range:SNR = 49.92 + 37.2 = 87.12 dB

author: fourfathom
author_rank: Super Contributor
timestamp: July 30, 2020, 10:24:22 pm
content: Quote from: radiolistener on July 30, 2020, 09:45:24 pmYes. [To some extent] You can see this effect in the one-bit delta-sigma D/A and A/D devices used in audio work. [But since this uses feedback it isn't quite the same thing.]And since the SDR sample rate is not coherent to the signal being detected we get an effective wideband dither which improves the narrow-band SNR. This dither is probably assumed in the bandwidth-effect calculations, I'm not brushed-up on the math. But I have designed quantization logic (in ASICs) that used high-frequency dither to good effect, greatly increasing the effective narrow-band resolution -- so I know it works.

author: radiolistener
author_rank: Super Contributor
timestamp: July 30, 2020, 11:12:05 pm
content: Quote from: fourfathom on July 30, 2020, 10:24:22 pmIt works like average. When you average several samples you will get sample with more bit resolution. The same thing happens in the filter which is applied in order to reduce bandwidth. Before do decimation, there is needs to apply filter to remove high frequency components (to prevent aliasing). So, after low pass filter the result samples will have more bits resolution.Reduce bandwidth for 4 times equals to add 1 bit to the sample resolution. This is why 1 bit = 10*log(4) = 6.02 dB

author: fourfathom
author_rank: Super Contributor
timestamp: July 30, 2020, 11:43:49 pm
content: Quote from: radiolistener on July 30, 2020, 11:12:05 pmYes, but you still need dither (noise or deliberate) or equivalent to make this work. Example: with a 1-bit A/D (a fixed-threshold comparator) digitizing a DC input you will only get one-bit resolution no matter how fast you oversample or how much you post-filter. Add the proper noise or dither to that DC input and then you can obtain *much* better quantization resolution after filtering.The asynchronous sub-Nyquist-rate sampling (or bandwidth-limited undersampling) also acts as a sort of dithering in the time-domain. I assume that this means that with input signals at or very close to integer fractions of the sample clock where the effective resolution is closer to that raw 49dB resolution of the 8-bit converter. I will try to play with this when I get a chance.

author: radiolistener
author_rank: Super Contributor
timestamp: July 31, 2020, 12:02:48 am
content: Quote from: fourfathom on July 30, 2020, 11:43:49 pmThere is no need dither for receiver, because there is atmospheric noise from antenna. Dither is needed when you measure some signal from device with no noise. But when you connect antenna, it already have enough noise for dithering

author: fourfathom
author_rank: Super Contributor
timestamp: July 31, 2020, 12:18:01 am
content: Quote from: radiolistener on July 31, 2020, 12:02:48 amYes, as I said. Just pointing out that something else is required for increased resolution. In this case, atmospheric or thermal noise is that thing.

author: cdev
author_rank: Super Contributor
timestamp: August 09, 2020, 06:50:44 pm
content: So, it seems that this dongle comes with the generic USB vendor and product IDs from Mirics which make it very similar to the previous Mirics dongles. (except that more of its antenna inputs are connected)http://blog.palosaari.fi/2013/10/naked-hardware-13-logitec-ldt-1s310uj.htmlIf it works with the free drivers it may be a lot like the sigrok situation.Does anybody know?

author: cdev
author_rank: Super Contributor
timestamp: August 25, 2020, 11:41:57 pm
content: If you are willing to use a translator or speak Chinese there is a bit of stuff about efforts to make DIY MSI SDRs on a chinese BBS, kehuang.org. Aparently the two main chips that are used to make an SDR cost so little its inspired a lot of people to try to make their own.Here are two examples:kechuang.org/t/83757kechuang.org/t/85213?page=0Nobody seemed so overjoyed with the results. however its kind of interesting.I donnt know if whomever made the blue dongle is a user there or not or where it stands in comparison to the other efforts.A German ham, recently put a lot of work into reviewing it, using the sdrplay software, not the free libraries."Measurements on an MSI SDR stick from Gerd DC6HL"https://saure.org/cq-nrw/2020/06/10/messungen-an-einem-msi-sdr-stick-von-gerd-dc6hl/

author: Gods69
author_rank: Newbie
timestamp: December 01, 2020, 02:42:58 pm
content: Quote from: A.Z. on July 27, 2020, 07:07:17 amHi,I also bought this receiver and it also does not have this electrolytic capacitor mounted on the PCB. I think he was soldered after.Worth it to put this decoupling capacitor? Thank you.

author: cdev
author_rank: Super Contributor
timestamp: December 04, 2020, 03:06:09 am
content: What kind of software supports the AD DAC as an SDR under Linux?I am not a windows user. Windows makes me ill, the stuff it does. I cant handle it and remain sane.So better not even try..However, I'd love to try building this into an SDR (assuming all thats needed is filters being it direct samples.. right?)it if it plays well with Linux.Quote from: radiolistener on July 29, 2020, 08:54:53 am

author: charliedelta
author_rank: Regular Contributor
timestamp: December 22, 2020, 08:30:30 pm
content: Stop playing with toys. Just buy a Perseus which gives you a great receiver, spectrum analyzer and measuring receiver all for the one price.

author: cdev
author_rank: Super Contributor
timestamp: December 22, 2020, 08:38:49 pm
content: Too expensive for me, last time I looked.Also, I still enjoy playing with toys.That said, there are fewer high dynamic range SDRs now that I would wish. Since then Ive looked into the actual commercial SDRplay and it doesnt look as good on closer inspection than I would hope either.If I had more in the way of programming skills, I'd definitely be interested in building a receiver or more likely, a ham transceiver kit.A big thing is software. Finding something that meets all of the various requirements isn't easy.

author: vinlove
author_rank: Frequent Contributor
timestamp: December 24, 2020, 10:40:13 am
content: I have a SDRPlay RSP1A, and the overload problem is not serious issue. When it overloads, you just scroll down the RF Gain to the level under the overloading, and all is fine. I find RSP1A a great SDR coverage from 1 kHz -2000 MHz all modes. I run it under the old Windows 10 loaded ACE laptop, kindly donated by my daughter.

author: A.Z.
author_rank: Super Contributor
timestamp: December 24, 2020, 11:01:32 am
content: Quote from: cdev on December 22, 2020, 08:38:49 pmSDRplay units aren't bad at all, same goes for AirSpy ones; sure, they aren't "ettus" or the like, but they offer quite a lot of bangs for the buck, plus there's quite a bunch of sw around (check github) to get one started, and then (but that will work for most/any SDR) there's the redhawk sdr framework which allows to use (or write) logical blocks and play quite a lot of cool experiments

author: HB9EVI
author_rank: Frequent Contributor
timestamp: December 24, 2020, 01:14:51 pm
content: indeed the RTL-SDR v3 are much better than their reputation; for that price it's tricky or nearly impossible to find something performing on the same levelI also have an RSP1 and a RSPduo, which perform well; under certain circumstances you can profit from the higher adc resolution/higher dynamic range, but not always. I think they are too high priced and in the end closed source, what I consider the biggest minus of it.

author: cdev
author_rank: Super Contributor
timestamp: December 24, 2020, 01:26:02 pm
content: Have you tried the rx-888? I don't know much about it.Seems like it could both receive and heat at the same time.Useful in the winter.Of course in Italy, probably not needed?The way I see it, If I am going to spend that much money, I should buy an HF ham transceiver kit with a general coverage receive capability. There are several options starting under $200.As far as bitness, it is hugely important. I have a softrock which uses my desktop's sound card, so it has the ADC resolution of the soundcard its used with. There is a really really huge difference between it and any RTLSDR on HF, with either an upconverter or direct sampling. I only hear the strongest signals on the RTLSDRs. Most are just invisible/down in the noise.When the softrock is properly calibrated (to cancel out the center spike) its much much more sensitive. All decent HF receivers are much more sensitive than any RTLSDR. The RTLSDR is however quite comparable to consumer electronics shortwave receivers.I hadn't really considered airspy recently, I forget why some reason I was not interested in them as a receiver. I forget what it is. Its been a long time since I compared all the cheap SDRs.

author: vinlove
author_rank: Frequent Contributor
timestamp: December 24, 2020, 02:27:24 pm
content: I had been interested in the original AirSpy in metal enclosure, but the latest version AirSpy Discovery+ was in plastic casing. It looked and felt cheap, and prone to suffer from RFI easily. And talking about high priced SDR, AirSpy was highest priced among all on sale.I looked elsewhere, and bagged a used RSP1A for the price of 2x new RTL dongles. I could't be happier than that. Although I am still not sure if AirSpy would be 4x times better performing than this used RSP1A. I bet they are more or less the same or similar performance, and really depend on what antenna they are fed with.

author: HB9EVI
author_rank: Frequent Contributor
timestamp: December 24, 2020, 02:29:37 pm
content: a QSD is still a way to go for SDR reception; both Elecraft KX2 and KX3 work like that; it's also a possible solution for IF-tapped ham transceivers.I'm running an OpenWebRX with 3 RTL-SDR v3 which work really well; digimode reception shows signals from all around the world; antenna is a simple active loop; additionally there are about 20m RG174 and 1:4 rf splitter in between antenna and every of the sdr sticks.a classis heterodyne ham transceiver is not all the time better than a SDR; also you don't have the feature of e spectrum scope without IF-tapping.

author: cdev
author_rank: Super Contributor
timestamp: December 24, 2020, 02:34:51 pm
content: They are both hugely important, and you're right in that its basically impossible to make the most of either one (antenna or receiver) if the other element is woefully inadequate. Are all of the upgrade from rtlsdr dongles fairly comparable?Only somebody like Leif Asbrink could tell us that. (expert on SDR receive parameters) They are probably within an order of magnitude of one another-One big issue with USB receivers is USB noise. I have a lot of ferrite CM chokes on my USBs and antennas and could probably benefit from even more. They should be fed in a way that decouples them from the indoor house ground. A unun at the antenna end thats grounded there will do it.Quote from: vinlove on December 24, 2020, 02:27:24 pmIs there anybody who has used the MSI.sdr receiver with the FOSS libraries who has had good luck with that?In other words, without sdrplay anything. Under linux.HB9EVI, or AZ, I am totally with you HB9EVI in wanting an open source SDR. Curious, have either of you ever compared the open source library (Libmirisdr or libmirisdr4 from github) with the closed source sdrplay libs running under Linux receiving HF??I should probably just keep my eyes peeled for a used SDRplay. If I could find one for the cost of the new MSI.sdr that would be much less of a gamble.Not using Windows, my options are significantly different on receivers.

author: cdev
author_rank: Super Contributor
timestamp: December 24, 2020, 03:10:32 pm
content: An active loop or magloop will pick up digimodes and I can receive signals from all around the world with my RTLSDRs and an upconverter or direct sampling.Just a lot fewer of them.One of my upconverters has a built in LNA and it does very well compared to the one I have that does not have receive amplification. (but requires a variable attenuator)To get better results I really need to get my antenna up a lot higher. I have two tall trees that since last year and a really big storm have been empty of antennas. Now they are bare and I should grab the opportunity to get a wire much higher up into them.The Softrock is a very simple Tayloe detector design, and according to Dan Tayloe his receiving detector can be "operated in reverse" which is kind of intriguing.. This has made me wonder if there might be an inexpensive mod to turn it into a transceiver that uses my existing hardware more efficiently.Need to get a ham license first, then start thinking about a rig.Quote from: HB9EVI on December 24, 2020, 02:29:37 pmIs your OpenWebRX online?

author: A.Z.
author_rank: Super Contributor
timestamp: December 24, 2020, 03:13:54 pm
content: ANY antenna will pick up "digimodes"

author: fourfathom
author_rank: Super Contributor
timestamp: December 24, 2020, 03:39:41 pm
content: Quote from: cdev on December 24, 2020, 01:26:02 pmFor what it's worth I've measured the direct-sampling HF sensitivity of the RTL-SDR Blog V3, with it powering a 20dB preamp, and I see a SSB noise floor around 0.005 uV (10 MHz single-tone SNR is 6dB with an input of 0.01 uV, using a 5 kHz audio bandwidth). This is possibly better than my Icom IC-7200 transceiver, which has a spec'd sensitivity of "less than 0.13 uV".For some tests I've used a resistive splitter to connect an antenna to both my IC-7300 and the RTL-SDR-V3, with the IC-7300 connected to a PC running WSJTX (WSPR) and the RTL connected to a RPi also running WSJTX. Running both rigs for 24 hours there was no significant difference in the number of signals decoded. I'm in a fairly quiet radio environment, so the results might have been different had there been strong interfering signals. I did put a narrow 10MHz bandpass filter in front of the preamp/SDR.Of course sensitivity is only one parameter, and the RTL certainly has its shortcomings. But it's good enough to be quite useful in some situations. I've linked this before, but this shows more about my system:http://wb6cxc.com/wp-content/uploads/2019/04/Presentation-1-0.pdf(The Finland station has since shut down due to RPi problems, and I haven't been back to fix things. I have also added 40-meter receive gateways at my two USA locations)

author: HB9EVI
author_rank: Frequent Contributor
timestamp: December 24, 2020, 04:24:49 pm
content: I tried running the RSP1 with libmirisdr; it's 'somehow' working, but far away from being satisfying; but that was a while ago already; maybe the lib got better in the meantime; maybe I'm going to try it once again

author: radiolistener
author_rank: Super Contributor
timestamp: December 24, 2020, 04:56:55 pm
content: Quote from: fourfathom on December 24, 2020, 03:39:41 pmHere is my measurement. RTLSDRv3 with -50 dBm 10 MHz sine on the input.S level is calibrated, so you can see actual dBm level on the grid.Noise floor for CW bandwidth 500 Hz = -120 dBm.It means MDS sensitivity for 500 Hz is -120 dBm = 0.224 uV.10dB S/N sensitivity is -110 dBm = 0.707 uV.Icom IC-7200 according to thespecificationat 10 MHz band and CW:10dB S/N sensitivity is -122 dBm = 0.16 µVAs you can see, Icom IC-7200 has 12 dB better sensitivity at 10 MHz band than RTLSDRv3 in direct sampling mode.

author: radiolistener
author_rank: Super Contributor
timestamp: December 24, 2020, 05:10:30 pm
content: Quote from: fourfathom on December 24, 2020, 03:39:41 pminteresting, can you show your mods for bias-tee from RTLSDRv3 on that LNA (page 17)?

author: fourfathom
author_rank: Super Contributor
timestamp: December 24, 2020, 05:35:11 pm
content: Quote from: radiolistener on December 24, 2020, 04:56:55 pmThis lines up fairly well with my measurements, where I have about 20dB preamplification (amp gain minus filter loss). Of course we have to consider the atmospheric noise floor and antenna gain before we know if any of this makes a difference in real-world sensitivity. My WSPR tests showed no significant difference.Have you made or seen any IMD / overload measurements for the RTLSDRv3? We can calculate using the A/D resolution, but I would like to see actual measurements. I still haven't done IMD tests, but have looked at the aliasing in the direct mode, which can be a big issue in noisy environments (and even the atmospheric noise gets aliased and added to the effective noise floor).

author: A.Z.
author_rank: Super Contributor
timestamp: December 24, 2020, 06:12:05 pm
content: regarding noise figures and IMD, the datasheet carries some infoshttps://rtl-sdr.com/wp-content/uploads/2013/04/R820T_datasheet-Non_R-20111130_unlocked.pdfthen, for sure, measuring "the real thing" gives the effective values

author: radiolistener
author_rank: Super Contributor
timestamp: December 24, 2020, 06:48:40 pm
content: Quote from: fourfathom on December 24, 2020, 05:35:11 pmYes, I tested it some years ago, it's about -49.6 dBc.Here is two tone IMD test with 2250 Hz between carriers.Also you can see dynamic range about 90 dB, because ADC input level is tuned to be about -1 dBFS.This is extreme measurementThe signal source is si5351 with two channel outputs connected together through SMA-T adapter.Each channel is configured for dedicated PLL: CH0=PLLA and CH1=PLLB.Carriers: 10000 kHz + 10002.250 kHz.Level is tuned with SMA attenuators, don't remember exactly, something like 6 dB at each channel then SMA-T and then some attenuator to fit full ADC range.

author: radiolistener
author_rank: Super Contributor
timestamp: December 24, 2020, 06:51:11 pm
content: Quote from: A.Z. on December 24, 2020, 06:12:05 pmR820T is not used in direct sampling mode

author: cdev
author_rank: Super Contributor
timestamp: December 24, 2020, 08:38:54 pm
content: Wonder how feasible it would be to take the data coming out of the tuner and sample it using another method, leveraging the tuner, but replacing the ADC ?Since the tuner chip is used in other similar devices, and the RTL is there to control it, simply bypass that part of the chain ?At the same time, replace the DC-DC converter also?I am not saying that would necessarily be better, although it might. I guess the USB data pipeline incolving the RTL could not be used because too much data. So it would be a real Frankenstein device.--- How does the HackRF One compare to the RTLSDR as far as SN and overload performance?Lets not forget that at its core the RTL was made to be sold profitably for just a few dollars.. It does remarkably well considering that. The RTLSDR blog version improves the things that it can improve and sells it for a slightly higher price but still the BOM cost must be fairly low.HackRF One components room is a bit higher.

author: cdev
author_rank: Super Contributor
timestamp: December 24, 2020, 10:19:55 pm
content: That would be great, you likely know how it should be fairly well owning the sdrplay hardware and knowing how it performs using that.The open version on github, libmirisdr4 incorporated several peoples work. I think it has not been developed past that version.Quote from: HB9EVI on December 24, 2020, 04:24:49 pmI'd like to build some kind of VLF MW receiver with more bits, maybe I will investigate whats needed to build a simple SDR using a Tayloe mixer, homemade filters and my Feeltech siggen (its a DDS siggen) and my computers sound card line input. That might be educational.

author: cdev
author_rank: Super Contributor
timestamp: March 05, 2021, 04:25:53 pm
content: I was wondering if you had done this, Ive been thinking about getting a "malachite" which uses an msi front end, and was wondering what its weak signal performance looked like to somebody with a lot of HF experience. (with external antenna of course)Thank you!Quote from: HB9EVI on December 24, 2020, 04:24:49 pm

author: hampolar
author_rank: Newbie
timestamp: November 02, 2023, 04:14:32 am
content: Imagine that hundreds of people are using cheap MSI SDR USB radio scanner and no one had problems like you describe. Anyway from what I see in your images you have a perturbation source nearby your house or in your region. If you want to be sure just scan the band with other scanner or ask someone to do it, you could have some band jamming from a power supply or other industrial equipment in your area or you just had some bad luck and get a broken sdr radio.

author: radiolistener
author_rank: Super Contributor
timestamp: November 02, 2023, 09:38:47 am
content: Quote from: hampolar on November 02, 2023, 04:14:32 amIf you read it carefully, the source of these spurs is MSi.SDR itself and it was tested with open input (nothing connected to it). There is no such interference in the house, you can see that RTLSDRv3 receiver don't show it. The same there is no such spurs on other receivers. I have no idea where you see "perturbation source nearby your house", because these spurs and beats are present on MSi.SDR only and it's frequency depends on LO setting.Quote from: hampolar on November 02, 2023, 04:14:32 amthis is possible, but I was seen screenshots and videos from other MSi.SDR owners and it shows the same issues. And their owners don't notice it, just because don't know how it should works or just don't have other radios to compare with...So, at least half of issues that I know are present on other MSi.SDR instances and some issues was confirmed on genuine RSP1It's more likely that you're just had good lack and get instance that works well, not like others. But I suspect that you're not very demanding and are not used to high quality sdr radio, so you're simply do not notice all these issuesIf you have MSi.SDR, we can test it, just let me know if you're ready to do test, I will prepare for you settings, you will record wav file with IF from your MSi.SDR instance and share it here, I will check if your device has these issues or not. So, we can check if you have the same "perturbation source"As a start point you can do this test:https://www.eevblog.com/forum/rf-microwave/cheap-msi-sdr-(sdrplay-rsp1)-clones-anybody-have-one/msg3158922/#msg3158922Quote from: cdev on March 05, 2021, 04:25:53 pmMalachite uses MSi tuner chip only and capture it's output with audio ADC, it don't uses MSi receiver chip. So, this is not correct to compare it with MSi.SDR or RSP1, they using different SDR stack. But it is well known that Malachite has frequency gaps and worse sensitivity than other portable sdr radio.You can find sensitivity and dynamic range comparison of Belka with Malachite on youtube.

author: p.larner
author_rank: Frequent Contributor
timestamp: November 03, 2023, 04:07:45 pm
content: are these the same talked of on this thread?https://www.aliexpress.com/item/1005003954483936.html?spm=a2g0o.productlist.main.5.1e9c290aRwpve4&algo_pvid=a04813b5-2429-4483-845f-d565500210f0&algo_exp_id=a04813b5-2429-4483-845f-d565500210f0-2&pdp_npi=4%40dis%21GBP%2115.09%2115.09%21%21%2117.87%21%21%40210387a116990270547681667e90bc%2112000034890967339%21sea%21UK%212308464272%21&curPageLogUid=R6qAhBzFB77u