HFU HF Underground
Technical Topics => SDR - Software Defined Radio => Topic started by: jon5500 on February 01, 2021, 1842 UTC
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Hello,
First time posting here and I am considering obtaining an SDR. I am no stranger to SDR's as I owned Softrock Ensemble II receivers (both LF and HF) as well as an RFspace SDR-14. The Softrocks did ok and I still have them, but not hooked up (was trying to get one working in the latest Ubuntu but a definite no go :)). My prize was the SDR-14 and I used it for listening to Jupiter back around 2010 or so. Being able to see and record full HF spectrum helped determine whether a emission was from Jupiter or not. Unfortunately, that SDR had to be sold due to much needed funding! I sort of regret that now as it was a wonderful performer.
So, sort of getting back into the swing of things. Over the last three years, I came across something that at least on the surface appears much like the SDR-14 and that's KiwiSDR. I don't know if it has direct sampling or not, but tuning into the many web based stations definitely shows full HF coverage simultaneously. The price appears to be significantly less than the SDR-14, although I do see one big drawback and it seems to need a web interface to work? It looks like for at least the board and that little computer it plugs into would run around $250 US or so.
Well, I'd still like to do better than that price and have the features of the Kiwi, assuming that it is, in fact, much like the SDR-14 was. I have read some threads at other sites suggesting sales sometimes of the boards, but I don't see that coming up very often. So, what about any Kiwi clones? Any comparable to the original or no go? Options other than Kiwi/ SDR-14 offering same features and quality (and less price)?
Thank you in advance,
Jon
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The KiwiSDR is direct sampling, with a 14 bit A/D. The CPU is built in, which is why you access it via a browser. One update is no software/driver issues. Plus you can share it online for others to use. And there's 4 independent receivers. A downside is no way to record I/Q for entire bands. I have several KiwiSDRs online, there's a list here: https://www.blackcatsystems.com/kiwi.html
You could consider the AirSpyHF+ Discovery, which is a fraction of the original price of the SDR-14, and more capable (I happen to have both).
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Thanks, the only issue I see with the Airspy is that it doesn't seem to cover the same bandwidth (768 Khz from what I read) as the Kiwi or SDR-14. Looking for something covering the entire HF.
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Thanks, the only issue I see with the Airspy is that it doesn't seem to cover the same bandwidth (768 Khz from what I read) as the Kiwi or SDR-14. Looking for something covering the entire HF.
The airspy covers all of HF (0-30 MHz) plus some of VHF. 768 kHz is the sampling bandwidth, you can view that much of the spectrum at one time. By comparison the SDR-14 was around 150 kHz.
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I have been using an SDRplay RSPduo for over 2 years now and am very pleased with it. Frequency range is 1 kHz to 2 GHz. The RSPdx would be a good choice. I use the RSPduo all the way down to 20 kHz with the loop antenna. The SDR puts my Collins, Harris, Racal and Watkins-Johnson receivers to shame. I would have a hard time going back to an analogue, rack mounted, receiver. As much as I am not a big fan of the Kiwi user interface I will eventually add one to my collection as a "remote receiver". --- Richard
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The airspy covers all of HF (0-30 MHz) plus some of VHF. 768 kHz is the sampling bandwidth, you can view that much of the spectrum at one time. By comparison the SDR-14 was around 150 kHz.
I'm not sure we're talking about the same figure. I'm referring to the maximum amount of bandwidth that can be viewed at once. With my SDR-14, this was the entire HF spectrum. Perhaps I should have said maximum display bandwidth as mentioned here: https://www.scannermaster.com/SDR_14_Receiver_p/43-501311.htm?Click=20907 which is 30 Mhz. Can the Airspy do this also? All I've found so far is the 768 Khz figure you mentioned.
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The airspy covers all of HF (0-30 MHz) plus some of VHF. 768 kHz is the sampling bandwidth, you can view that much of the spectrum at one time. By comparison the SDR-14 was around 150 kHz.
I'm not sure we're talking about the same figure. I'm referring to the maximum amount of bandwidth that can be viewed at once. With my SDR-14, this was the entire HF spectrum. Perhaps I should have said maximum display bandwidth as mentioned here: https://www.scannermaster.com/SDR_14_Receiver_p/43-501311.htm?Click=20907 which is 30 Mhz. Can the Airspy do this also? All I've found so far is the 768 Khz figure you mentioned.
We're not ;D That is a special sampling mode the SDR-14/IQ have, captures of raw A/D samples, so you can generate a waterfall of the entire HF band at once (though you cannot demodulate). Most SDRs don't have that capability, so if it is important to you, your options are limited.
The Chinese RX-888 & related SDRs always send raw A/D samples to the PC for processing, so that would be one option. They run around $200. I have one, they're not bad for the price.
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Unfortunately, I have had trouble with Chinese electronics almost every time I've made a purchase, so won't be going with those.
It looks like one of the earlier Airspy's had a special program written for it that would cover the HF spectrum, but the current unit doesn't support it. I should have mentioned early on I guess that I desired seeing the entire HF spectrum for crude spectrum analyzer purposes. I just didn't think the area would still be so specialized/ expensive, especially since the years have passed since the SDR-14 was in production.
Well, under the circumstances, I think I'll wait until I can at least get a Kiwi board on sale and pick up the Beagle somewhere else. Budget really is limited so have to watch funds closely.. I don't see the Kiwi coming up for sale used all that often, so the sale looks like the best bet.
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Well, under the circumstances, I think I'll wait until I can at least get a Kiwi board on sale and pick up the Beagle somewhere else. Budget really is limited so have to watch funds closely.. I don't see the Kiwi coming up for sale used all that often, so the sale looks like the best bet.
They have not had a sale on the KiwiSDR for some time (years). Demand has been far exceeding supply / Seeed manufacturing, so I would not expect a sale any time soon.
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Then I'll have to wait or look for a used SDR-14. I have seen those occasionally show up on the used market. In fact, the one I had I bought used.
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So, a bit of luck came my way, and it looks like I may be able to afford the Kiwi after all. I have a few questions:
1) Since the kit is unavailable, it looks like I will need a Beagle card and a 5V transformer based power supply, is this correct? Is GPS antenna really needed or can I forego that for now?
2) How reliable is the unit and/or card? History of failures, etc, welcome. I still debate whether it or the SDR-14 is the better choice, if I can find the '14 used. I read that at one point, there were Beagle card failures apparently due to manufacturing problems.
Anything else I should know?
Thanks again.
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So, a bit of luck came my way, and it looks like I may be able to afford the Kiwi after all. I have a few questions:
1) Since the kit is unavailable, it looks like I will need a Beagle card and a 5V transformer based power supply, is this correct? Is GPS antenna really needed or can I forego that for now?
The GPS antenna is not required, but highly encouraged, that's how the KiwiSDR corrects for errors in the ADC clock sampling frequency.
2) How reliable is the unit and/or card? History of failures, etc, welcome. I still debate whether it or the SDR-14 is the better choice, if I can find the '14 used. I read that at one point, there were Beagle card failures apparently due to manufacturing problems.
I've found the KiwiSDR to be highly reliable. Just don't apply the power backwards, or a higher voltage. The KiwiSDR online forum does have a few mentions of boards dying, but as there's about 5k of these out there (if serial numbers started at 1 with no gaps) that is not too bad.
While "better" is going to depend on usage, I have both an SDR-14 as well as the KiwiSDR. No comparison in my mind, the KiwiSDR is better overall.
Anything else I should know?
Thanks again.
You'll possibly want an SMA to (whatever) RF adapter for the antenna input, although the SDR-14 is SMA as well, so if you still have your old adapter from that, you're all set. Plus of course an ethernet cable and router/whatever to connect it to, the KiwiSDR does not have WiFi.
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Thanks, Chris. I do believe I still do have the SMA adapter around somewhere. I collected a LOT of adapters over the years. I also have several unused routers and I'll be using one for the unit. Would appreciate recommendations of a cheap GPS antenna and power supply. I assume it is best to not using a 5V switching supply. I probably have several "walwarts", but of course will have to check DC voltage output as they are often far higher than labelled.
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Any of the cheap units on Amazon (designed for 3-5 volts) will probably work fine, what they ship with the KiwiSDR itself is not exactly "top of the line" if you get my drift. Again not strictly mandatory for operation, so you can get up and running without one.
And yes, it is best to avoid any switching power supply. Some are not horrible and may work OK in a pinch, but in general most will cause some form of RFI issues.
There's a KiwiSDR document: http://kiwisdr.com/quickstart/#id-power that spec's what you want for the power supply, at least 2A is probably reasonable.
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Hi Jon - However, for the sake of clarity, the RX888 receives a bandwidth of up to 10MHz in the HF range. My Dell (i5-6300U 2core x64, 2,4GHz, 8GB) at 2MHz reception width locks up after short operation.
I am using Concole V3 which requires a powerful computer.
I also started the HDSDR program control, which is the least processor-intensive, but I do not remember if the PC was stable at the full 10MHz reception bandwidth.
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Mouser has some of the KiwiSDRs in stock, board only, you need to buy the Beagle CPU separately. If anyone is interested in getting a KiwiSDR, better hurry, these things sell out in a day or two, typically.
https://www.mouser.com/ProductDetail/Seeed-Studio/110060489/?qs=5hdTdOtYSo8Dmq6annahPw%3D%3D
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1) ... Is GPS antenna really needed or can I forego that for now?
The GPS antenna is not required, but highly encouraged, that's how the KiwiSDR corrects for errors in the ADC clock sampling frequency.
Does GPS also serve as a frequency/time reference? Can you also manually trim the reference or clock to WWV/CHU/whatever in absence of (or in addition to) that?
I notice that Kiwis can be anywhere from <10 Hz to as much as 60 Hertz (maybe more?) off from a standard. While that's not a life-or-death offset in a hobby listening scenario, it would be nice to be kind of on frequency when listening to SSB, where I notice being >10 Hz offset there.
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1) ... Is GPS antenna really needed or can I forego that for now?
The GPS antenna is not required, but highly encouraged, that's how the KiwiSDR corrects for errors in the ADC clock sampling frequency.
Does GPS also serve as a frequency/time reference? Can you also manually trim the reference or clock to WWV/CHU/whatever in absence of (or in addition to) that?
I notice that Kiwis can be anywhere from <10 Hz to as much as 60 Hertz (maybe more?) off from a standard. While that's not a life-or-death offset in a hobby listening scenario, it would be nice to be kind of on frequency when listening to SSB, where I notice being >10 Hz offset there.
The correction of the ADC sample also corrects the tuning frequency. Of course this depends on actually getting a good GPS signal. The supplied hockey puck GPS antenna is pretty marginal, I gave up on it and went with a NOS GPS antenna meant for the wireless phone industry for their towers.
It's entirely possible the KiwiSDRs you've encountered with large tuning errors have a poor GPS signal, or perhaps even none. Click on "Stats" in the control panel in the lower right corner of the KiwiSDR window. One of the entries is for GPS, it shows the number of tracked satellites. I checked one of mine and got:
GPSacq yes, track 12, good 11, fixes 41.5k
That means it is tracking 12 satellites (the maximum it can track) and has good signals from 11 of them, and 41,500 GPS fixes since the last restart of the software, which was 23 hrs ago (when the last software update was pushed through). The number of satellites is going to fluctuate over time. If you're interested in the nuts and bolts about GPS and the KiwiSDR there's been some good discussions on the forum: http://forum.kiwisdr.com/index.php?p=/discussions
At least 4 good satellites are required for frequency correction. So if you see fewer than that, it's not correcting. And even with 4 you don't know how good the signals are.
I suppose if you're on such a KiwiSDR, you could tune in CHU or WWV, see what the frequency error is, then compute the ppm error and apply that to the frequency of the station you're listening to. Note you need to treat it that way, it's not just a constant frequency offset error.
That said, a KiwiSDR with few or even zero GPS satellites is quite possibly the sign of a poor setup overall, including the antenna and noise/RFI levels. It would probably be easier to just find a better KiwiSDR to log onto. ;D
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I suppose if you're on such a KiwiSDR, you could tune in CHU or WWV, see what the frequency error is, then compute the ppm error and apply that to the frequency of the station you're listening to. Note you need to treat it that way, it's not just a constant frequency offset error.
That's exactly what I have done a few times to confirm my suspicions that some receivers were a bit off frequency.
I also suspected that the offset would increase with frequency and one time I went through the trouble of confirming this at 2.5, 5 and 10 MHz. It was incrementally worse at higher frequencies (by a few Hertz, but still..). (Could not hear 15, 20 or 25 MHz at the time.)
So there is no manual trim on the frequency with the Kiwi? I guess that would have to be some sort of override to the GPS, which, in my limited understanding, seems problematic
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So there is no manual trim on the frequency with the Kiwi? I guess that would have to be some sort of override to the GPS, which, in my limited understanding, seems problematic
The GPS based calibration works, but only if you have enough satellites. My guess is some users throw their GPS antenna on the desk and hope for the best. Often these same users hook up a coat hanger as an antenna and also hope for the best :)
There is a manual option KiwiSDR owners can perform, instructions from the KiwiSDR admin page:
To manually adjust/calibrate the ADC clock (e.g. when there is no GPS signal or GPS correction is disabled) follow these steps:
Open a normal user connection to the SDR
Tune to a time station or other accurate signal and zoom all the way in
Higher frequency shortwave stations are better because they will show more offset than LF/VLF stations
Click exactly on the signal carrier line in the waterfall
On the right-click menu select the cal ADC clock (admin) entry
You may have to give the admin password if not already authenticated
The adjustment is calculated and the carrier on the waterfall should move to the nearest 1 kHz marker
Use the fine-tuning controls on the IQ extension panel if necessary
You can fine-tune after the above steps as follows:
Open IQ display extension
Set the receive frequency to the exact nominal carrier (e.g. 15000 kHz for WWV)
Press the 40 button (i.e. sets mode to AM with 40 Hz passband)
Set menus: Draw = points, Mode = carrier, PLL = off
Adjust the gain until you see a point rotating in a circle
Use the Fcal buttons to slow the rotation as much as possible
The total accumulated Fcal adjustment is shown
A full rotation in less than two seconds is good calibration
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Often these same users hook up a coat hanger as an antenna and also hope for the best :)
Yeah, I've noticed.