I am basically using an RTL-SDR for SWL with an upconverter. I actually have several upconverters, two commercial ones and one homebuilt.
My typical SWL signal chain is a long wire antenna, around 60 feet of stranded wire, feeding into a 9:1 unun wound on a FT50-43 toroid, which is connected to both a good ground and its output goes right into a homemade 5 pole high pass filter tuned to around 2.3 MHz, which feeds into a 1:1 RF transformer of three turns on both the primary and secondary wound on a balun core of #43 material. the secondary goes right into the antenna input on an upconverter, via an adjustable signal attenuator. Then the output of the upconverter goes into the RTL2832 dongle.
The 1:1 transformer at the end, taking care not to let DC pass from the computer part to the upconverter/antenna part, makes a noticeable difference in reducing RFI. I think its because the computer/house AC system ground is noisy and the noise rides on the USB cable.
This combination works really well across the entire HF spectrum. I suspect its better than a lot of much more expensive setups, if you accept that you have to adjust the gain. Sometimes, with one upconverter I have - ( Thanks Adam! ) I have to turn the attenuator up up up. I was quite happy with it before but I keep discovering ways to get even more performance out of it.
I'm really enjoying a big improvement - super quiet signals with the addition of the little tiny homemade unun (15 minutes of work!) and another huge improvement Ive gotten from adding the homemade AM band block filter made on a little piece of perfboard with two coils wound on a form made out of a at (10 mm) purple drinking straw -one of those fat straws used for tapioca drinks.. the whole setup -including all the parts cost maybe $55-60.
Highly recommended. People are not going to be able to get this much flexibility any other way. I would expect to pay a lot more. Its also very small. The core of the hardware, enough to make for a pleasurable experience, the dongle and the upconverter and a USB extension and two ferrites fits in an Altoids tin. (Of course, you also need a computer.)
If you can live with occasionally switching the patch cables around this setup can receive fairly well from around (guessing) 300 KHz to a bit above 1750 MHz, continuously. I can receive 2.6 MHz without dropping any samples. If I can live with some issues, I can sample up to around 3 MHz. For some reason, I used to be able to sample up to the full 3.2 MHz using the USB3 input on my computer - that worked for a while but recently something, some upgrade or something seems to have killed my ability to use the USB3 on USB2 and get better performance. Now it just doesn't work. But, it works really well up to 2.6 MHz with no dropped samples at all.