Contemplating SDR

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ve3opc

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I am currently thinking about getting into the SDR scene as a good desktop receiver is pretty expensive by times ..my question more specific is how well do these units receive providing of course you have a half descent antenna ...is the sensitivity, selectivity on par with desktop radios. ?.
 

n9mxq

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My RTL-SDR V3 Receives as good as, if not a smidge better than my Icom IC-756PRO3 on the same antenna..
 

ka3jjz

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As this is a HF and below forum, let's stick to the topic generally - ve3opc, you might want to check out the various reviews we have linked in our wiki, and I'm sure there are more we don't have. One of the big things with the low-cost SDRs is that their front end filtering is often very poor or non-existant. You may need to invest in better filtering if you live in a metro area with lots of MW and FM BC around you. Those filters can be had at a modest cost, and no one can really 'recommend' one over another since everyone's RF environment is different.

Yes a decent antenna is a must - but not too long, for the reasons I just mentioned. Again this is going to be very RF area dependent.

Here's our wiki page with LOTS of reviews and manufacturers...

SDRs with HF Coverage - The RadioReference Wiki

Which are popular? Apart from the SDRPlay models, the Elads are also very popular. And if you really want to go for the gusto, the Perseus is the widely acknowledged king of the under USD1000 category.

You want to play before you buy? Fair enough - check out the list of online SDRs...

Live Tunable Receivers - The RadioReference Wiki

Mike
 

Token

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I am currently thinking about getting into the SDR scene as a good desktop receiver is pretty expensive by times ..my question more specific is how well do these units receive providing of course you have a half descent antenna ...is the sensitivity, selectivity on par with desktop radios. ?.

HF focused receive only SDRs run the gamut from under $50 to well over $5000, with performance differences to match the price spread.

I will only talk about HF SDRs I have or have used, and only models still sold today. Generally ascending cost point order below. Cost point roughly equates to performance, but of course that is not 100%.

The RTL SDR based receivers are tremendous bang for the buck, however they have issues. Only some RTL SDRs support HF, either with or without an upconverter, and there are dozens of models, so this is a general assessment without picking a specific model. In raw sensitivity they are normally plenty good on HF, but then sensitivity is seldom a problem for any radio on HF. And since selectivity is normally related to filter performance and the filtering of an SDR is in software and PC power, the filtering in a benign environment is generally quite good. Where these low cost SDRs typically fall on their face is image rejection, close blocking, dynamic range, and frequency stability / accuracy.

The Airspy HF+ appears to be quite good, however my time with it was very limited so I am not sure I am really qualified to say much about it.

The AFEDRI SDR is capable and not expensive. I use the dual channel version of it and when combined with SdrDX and two antennas it allows me to null / peak stations or interference.

The Kiwi SDR is a good value, but it is really meant to be remoted. The technical performance is decent and the ease of building a remote node with this is simply fantastic. Although other SDRs near the same price point may be technically a little bit better (generally not a big delta there), none are this easy to build a complete remote around. Some people don't like the browser based interface but it works for me.

The Elad FDM-S2 is a very good radio. I don't particularly like the software with it, but that is personal opinion. The software is very capable, and has many features, but for some reason I have not grown to like it. Without a doubt though, if you like the software this is a very good radio and competitive with some well known big name desktops.

The Microtelecom Perseus will compete with higher end hobby desktops. This SDR is getting a bit long in the tooth now, but is still a very good receiver.

The WinRadio G31DDC is a very good radio that will compete with past higher end hobby radios. This is my third most used radio and is very, very, good. Some people don't like the software interface, and it is not well supported by third party software developers, but I find the supplied software pretty good.

The RFSpace NetSDR with selected options is my most used radio. While possibly not quite as good a raw receiver as the G31 or G33, the tools the NetSDR brings to the table for my kind of listening make this my go-to radio for most of my efforts. The software options for these radios is about the widest out there.

The WinRadio G33DDC is simply World Class. It is my favorite receiver, although as I said the NetSDR is my most used. When combined with a decent computer with a good soundcard and good speakers / external amplifier it compares to the best of the hobby level receivers I have ever used. NRD-5X5, Drake R8B, Collins, etc. I compare it, as a receiver, favorably with most top end, contest, ham rigs I have used. It has the same software caveat as the G31DDC, but as I said, the software works for me.

The WinRadio G35DDC is everything the G33DDC is, plus the ability to record to hard drive the entire HF spectrum at one time (the G33 will only record 4 MHz of spectrum at a time, the G31 only 2 MHz of spectrum). The cost point of the G35 places it outside what most hobbyist would be willing to pay, and honestly I can't recommend it to most hobbyist. Not that it is not a good radio, it is simply outstanding. But the $5000 price point, more if you add options like 10 MHz ref, is hard to handle when the G33 is every bit as good without the 32 MHz record width capability and at a fraction of the cost. Unless you need to record 32 MHz of spectrum the G33 is the better selection for most listeners. Still, being able to press a button and record every signal from 0 to 32 MHz, for as long as you have hard drive space, is pretty nice. It has the same software caveat as the G31 and G33.

The WinRadio G39DDC compares to the G33DDC well, but at the price point of the G35DDC. It is focused at operations above HF, so most shortwave / HF listeners would never consider this radio. And although it is a good radio I really can't recommend it to an HF focused listener.

T!
 
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prcguy

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I didn't see the SRDPlay RSP2 series mentioned in Tokens post so I will give a recommendation for that. Its under $200 new and I can't think of any table top or portable SW receiver that can even come close in features and performance for that price. I doubt if you can find a good used analog SW receiver for the same price that will approach its performance.

I use a lot of high performance amateur HF rigs and have owned many premium HF receivers and my SDRPlay RSP2pro impresses me every time I turn it on. Its nowhere near the performance of an Icom PROIII as mentioned earlier in this thread but its better than a lot of HF receivers and transceivers that cost north of $1k or more new.

The newer breed of SDRs with 16 bit and greater ADCs is giving us performance and features we could never dream of for the price even 10ys ago. The little RSP2pro does more and appears to have better performance than a Hughes Aircraft SDR I worked with in the early 90s, which at the time cost about as much as a fine home in Beverly Hills.

I say you can't go wrong buying into one of the better SDRs mentioned in this thread and you will have a really good time playing with it. Even if you happen into a high end premium HF receiver in the future, there is still room for the SDR to do other tasks like becoming a spectral display for another receiver, or working bands and frequencies not covered by a stand alone desktop HF receiver.

Just get one. Do it!
prcguy
 

prcguy

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In most cases it should be possible to connect an SDR to the IF of an older analog AM/FM receiver to display what it is seeing. If you connect it after the first mixer ahead of the IF chain before any filtering you could get a little BW to look at before hitting any image frequencies or LO blow by.

The center frequency of the IF you would tune the SDR to would be different on an AM vs FM radio and you would want to know a little about receivers and proper way to make the connections. Common IF frequencies for broadcast AM receives is 455KHz and for FM broadcast 10.7MHz. You would also want to very lightly couple the receivers IF to the SDR via coax using a small value of capacitor, maybe just a few pf so you don't de-tune any circuits.

One of many problems I've seen doing this is the AGC action of the receiver taking over, running down the gain of the receiver when its tuned to a strong station and making the spectral display go up and down as you tune across stations. You will see a strong station off to the side on the spectral display and when you finally tune it in its amplitude can shrink to almost nothing on the spectral display. Very annoying.

An oscilloscope would usually connect somewhere in the audio chain of the receiver after the detector, much different and easier than tapping the receivers IF stage.
prcguy

Hey prcguy, Is it possible to connect a single SDR to a combined AM/FM stereo receiver or to separate AM and FM tuners to display their band spreads? What type of SDR could display a 2 MHz chunk of AM (540 khz to 1.7 Mhz) about a 1.7 MHz spread and a 20 MHz chunk of FM (88 MHz to 108 MHz) Would I need one or two SDR's to accomplish this? I've searched everywhere for the answer to no avail. What would I attach the SDR(S) to on the tuners? What SDR(S) would I need? Also I see some CB radios and AM/FM stereos with some time of external oscilloscope wired to them to show speech patterns. Thanks and enjoy your weekend.
 

ai8o

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The problem here is NOT the SDR.
The CRITICAL limiting factor is your computer.

I was using an ACER Aspire 7540-1284 under Win7.

I had an SDRPlay Rsp1.

The radio did fine RCVing SWBC in AM once I learned to turn off several constantly running default background services like MS automatic web upadate, and HP printer backgound service.

Also I had to narrow the waterfall bandwidth.

If I didn't, within a couple minutes the computer would overload, and all I would get was a Max Headroom like audio.

I was using HDSDR and UNO.

Both were bandwidth hogs.

I never did get any digital modes working.
Trying to get HDSDR, Virtual Audio Cable, and DM-780 , turned on in the correct order, AND running at the same time was a major PITA.
My laptop was just overwhelmed.

Again, the SDR is not your critical Limiting Factor!!!!!
The computer is!

Too much CPU speed and bandwidth is not enough.
 

Token

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Hey prcguy, Is it possible to connect a single SDR to a combined AM/FM stereo receiver or to separate AM and FM tuners to display their band spreads? What type of SDR could display a 2 MHz chunk of AM (540 khz to 1.7 Mhz) about a 1.7 MHz spread and a 20 MHz chunk of FM (88 MHz to 108 MHz) Would I need one or two SDR's to accomplish this? I've searched everywhere for the answer to no avail. What would I attach the SDR(S) to on the tuners? What SDR(S) would I need? Also I see some CB radios and AM/FM stereos with some time of external oscilloscope wired to them to show speech patterns. Thanks and enjoy your weekend.

Many SDRs will do the entire AM BCB natively (that is only 1.2 MHz width), no tuner needed in front of them. Of the ones I mentioned in my post, and keep in mind I am listing the maximum widths, you can zoom in for greater detail:

The low cost RTL SDRs will do up too about 2.8 MHz of bandwidth. However with the extreme variations in amplitude you have in the AM BCB the limited dynamic range of most of many of the RTLs may really bite you in the butt.

The AFEDRI SDR will display up to 1.6 MHz of bandwidth.

The Elad FDM-S2 will display up to 4.95 MHz of bandwidth.

The Perseus will display up to 1.6 MHz of bandwidth.

The RFSpace NetSDR will display with demodulation up to 1.6 MHz of bandwidth, and will display without demodulation up to 35 MHz of bandwidth.

The WinRadio G3XDDC radios are a bit unique, they have DDC windows that display spectrum, and you can demodulate anything in that window, and they have wideband windows that is for display purposes only. You move the DDC window around inside the wideband display if you want to record or demodulate. Picture here:
138333479.Ipbv6f16.all_three_basic.jpg


The WinRadio G31DDC has up to 2 MHz displayed in the DDC window (and this is the recordable spectrum), and up to 50 MHz displayed in the wideband window. You can dynamically zoom in on both windows without overwriting data.

The WinRadio G33DDC has up to 4 MHz displayed in the DDC window (and this is the recordable spectrum), and up to 50 MHz displayed in the wideband window. You can dynamically zoom in on both windows without overwriting data.

The WinRadio G35DDC has up to 32 MHz displayed in the DDC window (and this is the recordable spectrum), and up to 50 MHz displayed in the wideband window. You can dynamically zoom in on both windows without overwriting data.

Doing the entire FM band is a bit more challenging. Even if you tap the IF of an FM radio it (the IF) typically will not have 20 MHz of bandwidth. But if you could find something with that kind of IF bandwidth the NetSDR in 35 Mhz Real Time mode would show the entire FM band, and all 3 of the WinRadio G3X series would display up to 50 MHz on the wideband display, so you could get the entire band displayed with any one of them.

The Elad FDM-S2 will natively tune up to something like 170 MHz, so you can tune the FM BCB with it, but only display about 4.95 MHz of the band at a time.

The NetSDR+ has a built in VHF converter, that means it can tune up to above 1 GHz natively. But from 35 MHz up it limits the maximum displayed bandwidth in real time mode to 10 MHz, so you could only view half the FM BCB at a time that way.

Using the WinRadio G3X series on the IF of another tuner can display for you most of the FM BCB. And since the software has converter offsets you can make the displays show the correct information.

The following picture is the G33DDC on the IF of the Icom R8600. The 8600 is tuned to 98.0 MHz. You can see that the IF of the R8600 does not allow the full 88 to 108 MHzz range to make it to the G33. It starts to roll of about 92 MHz on the low side and about 106 MHz on the high side. Sure, you can see signals outside those points, but the levels are low as the response falls off. You could do the same thing with the RFSpace NetSDR in the Real Time mode, however the G3X series has the advantage of being able to demodulate audio while doing this, the NetSDR cannot demod in Real Time mode.

167018684.T3PBDH06.jpg


And here are some large images of the Elad S2, NetSDR, and G33DDC, each covering the AM BCB. I will make these links instead of embedding them though.

Elad S2 https://a4.pbase.com/o10/50/78250/1/167019062.9kBgXqvo.AMBCB_Elad_S2_18022018_0348z.jpg

NetSDR https://a4.pbase.com/o10/50/78250/1/167019063.BvV5NGie.AMBCB_NetSDR_18022018_0342z.jpg

G33DDC https://a4.pbase.com/o10/50/78250/1/167019061.zuiuXpT0.AMBCB_G33_18022018_0338z.jpg

T!
 
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Token

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The problem here is NOT the SDR.
The CRITICAL limiting factor is your computer.

I was using an ACER Aspire 7540-1284 under Win7.

I had an SDRPlay Rsp1.

The radio did fine RCVing SWBC in AM once I learned to turn off several constantly running default background services like MS automatic web upadate, and HP printer backgound service.

Also I had to narrow the waterfall bandwidth.

If I didn't, within a couple minutes the computer would overload, and all I would get was a Max Headroom like audio.

For most people it is a combination of things. As a general rule the computer can make a good SDR perform poorly, but even a great computer still cannot make a poor SDR good.

Here I have several computers running SDRs, as I type this at my listening desk 6 computers are turned on, 5 are running multiple SDRs. OS's range from XP Pro to Win 10. CPUs range from an old P4 HT to multiple CPU Xeons and i7s. The computers range from a 14 year old Compaq Presario Pentium 4 HT machine running XP Pro with 3 GB RAM, to a dual i7 8 core running Win 7 Pro with 64 GB ram. One of the computers is a Gateway SX2803-25e computer, Win 7 Pro and 6 GB of RAM (wiped, clean install of the OS and the features I wanted, not the Gateway bloat-ware), it cost $130 refurbed, and that one always has 2 SDRs running, 24 hours a day.

Ideally you do need some RAM, and you need some CPU speed, but really it does not have to be expensive. As is shown with my old Presario even a 14 year old machine can do the work, if you clean up the system and bump up the RAM.

T!
 
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spongella

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Here an RTL-SDR.com dongle and a Nooelec HamItUp converter works for me. A good outside antenna is a must as with all radios. I pick up all the shortwave, utilities, ham bands and VHF/UHF with no problem. Even decode RTTY, FAX, NAVTEX, etc., with it using MultiPSK.

I do find that this combo works well down to the AM BCB but the sensitivity on longwave is poor, even with a 43 foot vertical antenna attached. Not a deal breaker though. For the price there is really no downside.

Only thing with using this setup is learning to use a computer in conjunction with the receiver. It's not a plug and play situation but if you are reasonably computer literate it should be an easy lift.

Hope you find what you are looking for.
 

bob550

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My current HF setup is an SDRplay RSP2 and Icom R71A, both into a 70 end-fed long wire. One issue I have to deal with using the RSP2, and not with the Icom, is overloading of strong MW AM broadcast signals. However, the RSP2 has built-in filtration to attenuate MW signals and helps reduce the overloading. I'm also using a high-pass filter that provides further attenuation of these MW broadcast signals. Overloading aside, I find the SDR a joy to use, and I can receive everything my R71A can. But unlike the R71A, I can simultaneously "see" a wide range of frequencies, with the spectrum scope and waterfall display, that the Icom can't.

The software you choose will make a huge difference in your enjoyment. I have currently settled on SDR Console, but have also used SDRSharp, SDRuno, and HDSDR for HF. Console has the ability to create your own bandwidth filters. That is if you're unsatisfied with the several choices already configured. The digital noise reduction is fantastic! You can also create up to 6 independently selctable "receivers" or VFO's that memorize frequency, mode, and bandwidth settings.

I began my SDR "career" with the Nooelec NESDR Mini for VHF/UHF, moved up to the RTL-SDR Blog V3 that included HF coverage, and ended up (for now) with the SDRplay RSP2 covering 1kHz to 2GHz. The RSP2 has separate software-selectable antenna inputs for both VHF/UHF and HF.
 

dave524

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My current HF setup is an SDRplay RSP2 and Icom R71A, both into a 70 end-fed long wire. One issue I have to deal with using the RSP2, and not with the Icom, is overloading of strong MW AM broadcast signals. However, the RSP2 has built-in filtration to attenuate MW signals and helps reduce the overloading. I'm also using a high-pass filter that provides further attenuation of these MW broadcast signals. Overloading aside, I find the SDR a joy to use, and I can receive everything my R71A can. But unlike the R71A, I can simultaneously "see" a wide range of frequencies, with the spectrum scope and waterfall display, that the Icom can't.

.

Same SDRplay RSP2pro and Icom R71A here, medium wave is a problem on the SDR cause there is 3 Toronto AM stations that saw fit to put their arrays on the south shore of Lake Ontario near Grimsby . But I do like the ability to see a chunk of bandwidth on the waterfall and it ears are pretty much as good as the Icom, plus it gives me more modes than the old RS Pro 2006 on UHF/VHF if you are into that sort of thing too.
 

scoobis

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Overloading is not a problem i have yet to experience any overloading with the AirspyHF+ and i have very close stations to me, 3 BCB stations within a mile.

i still don't like the strong signals hitting the receiver front end so and have permanently installed a -40db BCB filter. the airspyHF+ is so sensitive that it doesn't affect my ability to DX BCB actually. for anyone who cares, I'm using the noelec Distill:AM Barebones - Broadcast AM Bandstop filter. The name is kind of a misnomer, -40db is far from blocking anything.

its a good filter, it doesn't affect anything outside the BCB though the lower and upper ends of the BCB are less attenuated as you might expect. they have a full sweep posted on their site. id highly recommend it if you are getting overloading. I was able to get my strongest signal, which was getting close to -10dbfs, down to -20DBFS which just means the AGC isn't attenuating much. I'm still able to receive the weakest of BCB signals. Though i attribute that to the wide dynamic range of the airspyhf+
 
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RFI-EMI-GUY

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I am looking to tap the IF of my IC-R9000 receiver so that I can use an SDR as a wide panoramic display and digital mode demodulator. The IC-R9000 will do all the heterodyne conversion and front end filtering that a modest priced SDR lacks.

In the price range I am considering $250, the ultimate selectivity of these devices seems to be a couple MHz down to 192 KHz. Good for a panoramic display , but not so good for direct reception of narrowband signals like SSB.

Any recommendations in that price range? How many bits resolution should I seek?
 
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prcguy

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You might find out of the IF out on your R9000 is affected by AGC. My R7100 is and it made the IF output nearly useless with a spectrum analyzer.

If you see a big signal off to the side with a spectrum analyzer (or SDR) and tune towards it, as it gets within the receivers IF filter BW the AGC takes over and knocks it down to almost nothing. As you tune through signals it looks like they are getting sucked into a void in the middle of the spectrum analyzer.

You could probably check this by generating a signal 50 or more KHz away from center of what the R9000 is tuned to, use a separate receiver to receive that at IF +/- 50KHz, note the level then tune the R9000 right to the signal and tune the separate receiver to the IF center and see if its the same level. Did that make sense?
prcguy

I am looking to tap the IF of my IC-R9000 receiver so that I can use an SDR as a wide panoramic display and digital mode demodulator. The IC-R9000 will do all the heterodyne conversion and front end filtering that a modest priced SDR lacks.

In the price range I am considering $250, the ultimate selectivity of these devices seems to be a couple MHz down to 192 KHz. Good for a panoramic display , but not so good for direct reception of narrowband signals like SSB.

Any recommendations in that price range? How many bits resolution should I seek?
 

RFI-EMI-GUY

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You might find out of the IF out on your R9000 is affected by AGC. My R7100 is and it made the IF output nearly useless with a spectrum analyzer.

If you see a big signal off to the side with a spectrum analyzer (or SDR) and tune towards it, as it gets within the receivers IF filter BW the AGC takes over and knocks it down to almost nothing. As you tune through signals it looks like they are getting sucked into a void in the middle of the spectrum analyzer.

You could probably check this by generating a signal 50 or more KHz away from center of what the R9000 is tuned to, use a separate receiver to receive that at IF +/- 50KHz, note the level then tune the R9000 right to the signal and tune the separate receiver to the IF center and see if its the same level. Did that make sense?
prcguy
I have heard of that problem. I will have to look and see how the internal spectrum display is tapped.

Sent from my SM-T350 using Tapatalk
 
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