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Technical Topics => SDR - Software Defined Radio => Topic started by: Matt285 on February 27, 2018, 2026 UTC

Title: SDR receiver basic questions
Post by: Matt285 on February 27, 2018, 2026 UTC
I have done a little bit of SDR research, but have a few questions. Does all SDR software show you what you are listening to? example if i'm on a frequency on the 49m band, it will list Radio Havana? does it tell you all of the Utility/Volmet/Numbers stations etc with fair accuracy? Last question is -What is a reasonably priced set up including dongles,misc cords etc? Thanks!

P.S I know its hard to answer the question with so many on the market.
Title: Re: SDR receiver basic questions
Post by: fpeconsultant on February 27, 2018, 2128 UTC
If Matt doesn't mind my jumping into his questions, I have a few:
What type of computer horsepower is needed for a "mid $ range" SDR?  And is the connection between the SDR unit and the computer made thru where I'd plug in an Internet cable (looks like an old school telephone jack but wider)?
Thx for any help & thx Matt for starting this topic.
Title: Re: SDR receiver basic questions
Post by: ChrisSmolinski on February 27, 2018, 2150 UTC
I am able to run SdrDx on an older (about a decade old) MacBookPro. I am also able to run SDR Console on a fairly old and not powerful i3 Windows laptop.  You don't need a state of the art computer.

Most SDRs use a USB interface. Some (like the AFEDRI and netSDR) use an ethernet cable. I prefer the latter (no need for drivers, although AirSpyHF+ managed to make it work without any driverrs), although I understand the desire for the former, as the USB cable provides the power.

There's a nearly infinite number of SDR programs out there, with different features. SdrDx, for example, plays nicely with my DX ToolBox program, and uses its database of SW transmissions to list what station(s) you're tuned to.

IMHO your best bang for the buck right now is the AirSpy HF+ at $199.  Next I'd say the AFEDRI units. Lots of folks have the SdrPlay and seem happy with them, I have no experience. They cost less than the AirSpyHF+, from direct comparisons I have seen, they do not perform quite as well.  Then you your top tier SDRs, like the netSDR, Perseus, etc. which are in the $1500 and up range. I have a netSDR, it is my main radio. I also have a NRD 545, it's gathering dust. That's how good the netSDR is  ;D

Please stay away from the RTL dongle/upconverter combos for HF work. For VHF/UHF work, the RTL dongle is a very good value. But not for HF. Once you get the dongle and converter, and that whatever filters you need to make it sorta kinda work (if you don't look too hard), you're a significant percentage of the way towards something much more functional and useful.
Title: Re: SDR receiver basic questions
Post by: fpeconsultant on February 28, 2018, 1902 UTC
Chris - thx thx.
So the Air Spy HF+ connects to the computer via a USB port?  And the antenna is connected to the AirSpy unit via a regular old coax connector?  And once one has the black box, all that is needed is to download software from the Airspy website?
Dumb questions I'm sure - sorry for that!
FPE
Title: Re: SDR receiver basic questions
Post by: ChrisSmolinski on February 28, 2018, 1906 UTC
Yes, regular USB cable. And it works with several SDR programs out of the box, like SDR Sharp and SDR Console. Also SdrDx on the Mac with my AirSpy Server app.

The AirSpyHF+ has SMA connectors, so you need an adapter. SMA to F adapters are cheap and easy to find, and I use F connectors on my coax here, so that worked perfectly. I think you can buy SMA to UHF adapters as well, if you use PL-259s.
Title: Re: SDR receiver basic questions
Post by: Josh on February 28, 2018, 1916 UTC
I run a RSP2 via a Intel Q6600 quad core (ie old and slow) pc on 32bit win7.
The sdr apps I use most are HDSDR and Console V3.

HDSDR has the lowest cpu usage of all the sdr apps I've tried and it works very well. With the eibi csv files you have a quick and built in means to see what is goin on in and around the freq you're tuned to in HDSDR as far as mode, user, etc.
If HDSDR had multiple vrx capability I'd use it full time, but it doesn't.

So I use Console V3 for multiple vrx work. I love the audio of SDRuno, and it does vrx too, but it takes a good deal more cpu time in vrx as well as single receiver mode.

Right now I have Console V3 up with 3 vrx, a decoder for Mil 110A mode, and another decoder running ale and HFDL.
The current cpu loading is between 3 and 8 percent. I've run up to 10 vrx in Console V3 and it only used about 30 percent cpu time. A faster system would show even lower loading, but my old pc is just fine for the monitoring I do.

One trick when using a low power pc to play sdr is to make sure nothing else is running that will take cpu time.
Title: Re: SDR receiver basic questions
Post by: Stretchyman on February 28, 2018, 2003 UTC
No, the SDR is just a down converter and not some intelligent computer thingy so you'll get ZERO info on the screen just a load of wiggly lines (signals).

However you can annotate them and there's probably a massive DB building up out there somewhere? (Thanks Chris)

Just buy an SDRPlay, RSP1A/2/pro depending on how much you want to spend.

Yeh there's loads of others but the cheap ones are crap and the expensive ones are, well.. expensive.

You pays ur money....

OK!


Str.


Title: Re: SDR receiver basic questions
Post by: fpeconsultant on February 28, 2018, 2035 UTC
Thx to everyone for their help.  Confusing lingo for an old school dial turner.
Back to the R8, JRC 545, Ten Tec RX 340 and WJ HF 1000 I guess....
Title: Re: SDR receiver basic questions
Post by: MDK2 on March 01, 2018, 0329 UTC
Thx to everyone for their help.  Confusing lingo for an old school dial turner.
Back to the R8, JRC 545, Ten Tec RX 340 and WJ HF 1000 I guess....

Don't be too put off by some of that. "Multi VRX" means that you can use the software to run multiple receivers (or virtual receivers, which is where the 'VRX' shorthand comes from) from one actual SDR unit. It is a pretty cool feature.

I got into this with my only experience being with a Tecsun portable and a Satellit 750, neither of which are a "real rig." It was a steep learning curve but oh so worth it.

SDRplay has probably the best online presence for helping a newbie out. They have groups on Facebook and Yahoo and their people are always involved in all of them, answering questions quickly. If you use their proprietary SDRuno software, there is also a series of very helpful videos on youtube to help you with basic configuration and operation. So although it's not as good for the money as the Afedri or Airspy HF+, that support makes it a good place to start. And take it from someone who knew almost nothing when I got mine, you can learn it.
Title: Re: SDR receiver basic questions
Post by: fpeconsultant on March 01, 2018, 1544 UTC
Thx for the encouragement - I would like to give it a try & probably will - thx everyone for the help & feedback.
FPE
Title: Re: SDR receiver basic questions
Post by: Rob. on March 01, 2018, 1846 UTC
Once you go SDR, you'll never go back :D

The learning curve isn't too bad once you get it up and running. If you are a hands-on type of learner just get one and start playing. I have the Afedri-NET receiver and like it a lot because I can be on any computer in the house and still control it.

Title: Re: SDR receiver basic questions
Post by: ChrisSmolinski on March 01, 2018, 1850 UTC
Once you go SDR, you'll never go back :D

This. Without my SDR I would only hear a fraction of what I do now. Once you start seeing the entire band at once, going back to a radio with a knob and single frequency display is difficult.  May as well go back to a crystal radio.
Title: Re: SDR receiver basic questions
Post by: fpeconsultant on March 01, 2018, 2018 UTC
As Bob Dylan said "the times, they are a-changin' "
Title: Re: SDR receiver basic questions
Post by: Stretchyman on March 01, 2018, 2051 UTC
Recording a spectrum, visually too is kinda wierd but the guvmints being doing it for years, now you can too!

Get one, seriously interesting

Random nonsense, I could go on...!

Str.
Title: Re: SDR receiver basic questions
Post by: Josh on March 01, 2018, 2124 UTC
Lol, if you have a 340 and wj1000 you already have sdr rigs. Stand alone sdr rigs like perseus, afredri, rsp just lack the gui and controls that are in hardware with the 340 and 1000, the pc screen and kb/mouse make up for for the lack of a display and tuning knob. Isn't there a IF output on both the 340 and 1000? All you'd have to do is feed that IF signal to a cheap rtl dongle and use most any sdr app to see (as well as hear via vrx) what is in the IF stream of those fine rigs. Also you'd be hard pressed to find a inexpensive sdr that is anywhere near the performance levels of the 340 and 1000.
Title: Re: SDR receiver basic questions
Post by: ChrisSmolinski on March 01, 2018, 2200 UTC
Lol, if you have a 340 and wj1000 you already have sdr rigs. Stand alone sdr rigs like perseus, afredri, rsp just lack the gui and controls that are in hardware with the 340 and 1000, the pc screen and kb/mouse make up for for the lack of a display and tuning knob. Isn't there a IF output on both the 340 and 1000? All you'd have to do is feed that IF signal to a cheap rtl dongle and use most any sdr app to see (as well as hear via vrx) what is in the IF stream of those fine rigs. Also you'd be hard pressed to find a inexpensive sdr that is anywhere near the performance levels of the 340 and 1000.

The 340 and WJ1000 are good radios and use DSP (a la the NRD-545), but are not SDRs.  Many radios have an IF output (even my ancient R-71A has one) but that doesn't make it an SDR. In fact, having an IF output pretty much confirms a particular radio isn't an SDR, at least not a DDC SDR  :P
Title: Re: SDR receiver basic questions
Post by: Traveling Wave on March 02, 2018, 2101 UTC
Josh has a good point. I have a Kenwood TS480 and I use a cheap RTL Dongle that is fed by the 1st IF stage of the TS480. The dongle is then connected to the laptop RS232 port. I run HDSRD software for the SDR display and use Omni-rig for rig (interface) control software. Both Omni-rig  and HDSDR are free. Omni-rig supports the following transceivers and radios....

•TS-440, TS-480, TS-570, TS-590, TS-690, TS-850, TS-870, TS-930, TS-2000, all other Kenwoods
•FT-100D, FT-450, FT-747, FT-757, FT-817, FT-840, FT-847, FT-857, FT-897, FT-900, FT-920, FT-950, FT-990, FT-991, FT-1000, FT-1000MP, FT-2000, FT-9000, FTDX-3000, FT-DX5000MP
•IC-78, IC-275H, IC-703, IC-706MKII, IC-706MKiiG, IC-718, IC-725, IC-726, IC-728, IC-735, IC-737, IC-738, IC-746, IC-746Pro, IC-751,IC-756, IC-756Pro, IC-756ProII, IC-756ProIII, IC-761, IC-765, IC-775, IC-781, IC-821, IC-910, IC-970D, IC-7000, IC-7100, IC-7200, IC-7300, IC-7315, IC-7410, IC-7600, IC-7610, IC-7700, IC-7800, IC-7850, IC-7851, IC-9100, IC-R75, IC-R8500, IC-R9000, IC-M70
•CODAN, Elecraft K2, Elecraft K3, Ten-Tec Eagle, Ten-Tec Paragon II, Ten-Tec Orion, Ten-Tec Jupiter, Ten-Tec Omni VI+, Ten-Tec Omni VII, TenTec RX-350, JST-245, DX-77, NRD-535(DG), PowerSDR, Perseus, FRG-100, ZS-1, Elad-FDMSW2, ADT-200A, AOR AR5000, AOR AR8600, SmartSDR

Lastly, you may not need to tap the IF stage if your radio has a receive out and a receive in. Check you-tube to find this method of hook up.
 

 
Title: Re: SDR receiver basic questions
Post by: fpeconsultant on March 02, 2018, 2126 UTC
You guys (?) all better be careful because if I do make the jump to an sdr, you'll be dealing with lots of probably really dumb questions from me!!
Thx again to all of you,
FPE
Title: Re: SDR receiver basic questions
Post by: Josh on March 03, 2018, 2011 UTC
You're well set for program listening/pirate hunting/dxing as is with the knob radios.
Where the bespoke sdr shines most is in digital mode decoding. I view the sdr rigs as I do the R390A, great for monitoring a specific channel or set of channels, not so great at cruising a band. Also the knob radios don't need the pc running just to function as a radio. Anyway, here's what is spread across two monitors as I compare hfdl decode performance between decoders, the sdr is an RSP2 fed with a off center fed dipole. The RSP is controlled by Console v3 and has 3 vrx in operation.
Amazing the sdr capabilities of today, and for so little money too. What used to be a room with dozens or hundreds of R390As consuming 115 watts of power each plus attendant devices and maintenance personnel is now reduced to a little black box a bit bigger than a pack of cigs costing less than $200.
Title: Re: SDR receiver basic questions
Post by: ThElectriCat on March 06, 2018, 0025 UTC
Hopefully this post isnt too long, but I feel it may be helpful

The SDR can be divided fairly cleanly into three parts
the hardware
the operational software/firmware
the user interface. 

Most of the time, the lower end (<$1k) radios combine the software and user interface, and the higher end ones typically have some of the operational parameters written in firmware (one time code on an FPGA) and do only the second half of the radio operations on the host computer (the one you plug the SDR in to.)
          The ideal SDR (the one that is truly "software defined") would perfectly digitize infinite RF spectrum with no noise, error, or limits (not possible) and do all of the radio parts there.
          The real SDR usually has some form of down conversion, and always has some form of filtering. and then the remaining parts of the reception and demodulation are done in software. 

the fundamental point of all this is that an SDR cannot have any functionality that a traditional analog radio cannot have.
All parts, filters, mixers, local oscillators, multipliers, must be implemented in software just as they must be in hardware in an analog radio. 

That being said, there are many things that are possible in software that although technically possible in real hardware, are not practical, a 100 pole filter, fft, or fully adjustable equalizer for example.

so to put it briefly, no an SDR will not provide you with anything a traditional radio cannot. 

instead, what the SDR really gives you is the ability to model a "real" radio in a way that is infinitely alterable, and free from inaccuracies like component tolerance or stray capacitance.

that being said, the application that runs the SDR (of which there are probably over 1000) could be written to search the internet for whatever frequency you are tuned to and display that page in the database to give you a real time callsign readout.

P.S, I like the HackRF ONE, even though it has a poor noise figure, it can transmit as well as receive, and makes for quite a piece of budget test equipment.
Title: Re: SDR receiver basic questions
Post by: Token on March 06, 2018, 0049 UTC
Many radios have an IF output (even my ancient R-71A has one) but that doesn't make it an SDR. In fact, having an IF output pretty much confirms a particular radio isn't an SDR, at least not a DDC SDR  :P

Some DDC SDRs do have an IF output.  For example the Icom R8600 has an IF output.  Above 30 MHz it downconverts, so in those bands it is not a DDC but rather a hybrid, VHF+ downcoverted to base band.  But below 30 MHz it is DDC.  I have not seen a full schematic, and so far have only seen a simplified block, so I am not sure how the radio gets filtered and tuned IF out while being DDC on 0 to 30 MHz, but that is the claim.

T!
Title: Re: SDR receiver basic questions
Post by: ChrisSmolinski on March 06, 2018, 1215 UTC
Some DDC SDRs do have an IF output.  For example the Icom R8600 has an IF output.  Above 30 MHz it downconverts, so in those bands it is not a DDC but rather a hybrid, VHF+ downcoverted to base band.  But below 30 MHz it is DDC.  I have not seen a full schematic, and so far have only seen a simplified block, so I am not sure how the radio gets filtered and tuned IF out while being DDC on 0 to 30 MHz, but that is the claim.
T!

I've seen some speculation that the 10.7 MHz IF for HF is regenerated from the sampled data. So it's more a "virtual" IF than "real" IF, but effectively the same from a user point of view.
Title: Re: SDR receiver basic questions
Post by: Token on March 07, 2018, 1055 UTC
I've seen some speculation that the 10.7 MHz IF for HF is regenerated from the sampled data. So it's more a "virtual" IF than "real" IF, but effectively the same from a user point of view.

I have seen the same speculation, and I honestly do not know.  However, I think, based on the observed operation of my R8600, that this is not how it is done.

If the IF of the R8600 was regenerated sampled data you would expect that the displayed IF bandwidth would be pretty consistent, related as it is to the sampled data and the sampled data having some fixed maximum sampled width.  The maximum displayed bandwidth of the R8600 is about 5 MHz, so I would expect any regenerated IF to be a bit more than 5 MHz of width.

However what we really see is variable bandwidth on the IF that seems to be tied to the bandpass filters, and sometimes over 14 MHz in width.

Also, on HF below 6 MHz there is a definite image in the IF that is on the upper side of the IF freq (10.7 MHz) plus 2x the tuned freq, this can equal an IF bandwidth of well over 15 MHz, with half of it being an image.  If you stay +/- 3.5 MHz of the 10.7 MHz IF center freq you will never see this, and it is no issue, but if you look out wide you can see it.  Also there is a birdy/LO leakage that is always tuned freq above the IF center freq.  I suppose this could be DC if it was all regenerated sampled data.

To me the IF is acting more like some kind of mixed signal product rather than some regenerated data.  But like I said, I am not sure.  If I have time this weekend I will break out the test equipment and try and get a better hand on what it is doing where.

T!