Have you ever used any of the more professional SDRs? (with the exception of the HackRF which is also 8 bits)
the reason I ask is because the difference is dramatic, in terms of weak signal reception. I like the dongles, I just don't think its worth spending a lot of money on fancy ones or add ons for them that would be better spent on simply getting a better SDR.
As the cheapest ones in my experience work as well or sometimes even better than the more expensive ones.
The dongles are great. For $10-15 they offer fabulous value. They also make a good IF for single purpose custom hardware- making it very easy to make all sorts of dedicated radio devices cheaply.
I'll reserve judgment on "SDR-play" until I've tried one. I have heard mixed reports.
There is a lot of benefit to be gotten with almost all SDRs by using non-digital, physical band pass filtration.
My only experience with SDR has been NooElec and SDRPlay. I saw that you could add the NooElec HamItUp converter to the NooElec dongle but after reading lots of reviews I decided to go for the SDRPlay.
What SDR is doing is providing a learning test bed. I don't know if I will go further up the food chain; kind of depends on what I learn. I like good quality signals (used to be into hifi). My experience with the best FM (analog) tuners were that they sounded better than the digital tuners - that was several years go so maybe things have changed. People here will probably say phooey but that was what my ears told me. In any event, I'm very sure that some systems - from signal creation to signal recreation - sound better than others. It depends on everything from how the source was captured to the amplifying electronics to especially speaker design, speaker locations in a room, and room acoustics. On the other hand, my interest in EEVblog type electronics and SDR is not to achieve super hifi quality music it's to gain some hands on experience with RF, baseband, and A to D / D to A - so the only reason I'm mentioning audio quality is that I think it makes sense to establish a frame of reference on what is (admittedly subjectively) discernible on a pretty strong and well know signal before listening for ET on the airwaves. (Actually awhile back I discovered HAMs have been doing EME "Moon Bounce" - so I realize there is a point at which just sending and receiving a signal can be an extremely impressive feat even when the end result is truly barely discernible.)
Anyway, back to SDR....
One of the things I'm enjoying with the SDRPlay is the ability to look at 8MHz of bandwidth and then to narrow in and tune in once a signal of interest is identified. The relationship between the IF bandwidth and the sampling rate along with the IF gain are all very interesting; the ability to graphically as well as acoustically experience the results makes a very good learning platform. And it's raising TONS of questions.
Attached is a screen shot of a FM station signal. I think it's being sampled at rate of 192 kHz. The ExtIO graphic says the bandwidth is 600kHz which I presume must be the entire left to right blue section of the signal shown in the large panel (minus the rolloff on either side). Or perhaps the IF bandwidth is what is shown in green rather than blue?
As the second image shows the light blue vertical highlight is narrowed when the sampling rate is lowered from 192 kHz to 107795 Hz. In some respects the sound improves when the sampling rate is reduced - perhaps the lower sampling rate is reproducing less noise and effectively improving the signal to noise ratio, or maybe it's just putting more music into the signal and raising the gain? (Sometimes louder sounds better even if it isn't.) I noticed that changing the FM-BW sampling rate (reducing it from the max setting via the vertical slider) not only changes the signal audibly but the characteristics can be seen in the lower right panel that I think is the 15 KHz FM signal. To me, the ability to see the signal from all these perspectives is fascinating.
Net, net: what is the thinking on optimizing the tuning when using the IF bandwidth and sampling controls? And the IF gain control? (I've decided to uncheck the LNA EN in check box ExtIO - it provides too much gain, I think.) I'm betting there is some preferred sequence and technique for tuning into signals - I just haven't figured it out yet.
On a related question, I'm guessing that the two humps next to the main signal are the upper and lower side bands. I'm wondering why they have more of square top and less of a pointy top? Also, all the small vertical white lines, are those what are referred to as "birdies"? What causes them? Back to amplitude, it seems that where the blue turns to green might be about where the blue sampling highlight intersects? Any significance to this being where the sound quality and gain sounded good, or just a coincidence?
Thanks for any insights. EF