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!