It bears pointing out that the upconverter boards work better than the mods that simply bypass the tuner and feed the RF signal directly to the ADC chip.
Using the upconverter, the signal is cleaner and quieter, and can take stronger off-band signals without distorting.
The Nooelec Ham It Up 1.3 upconverter also has an area on it to add integrated wideband noise output, which can be used for antenna and filter testing with the addition of a Return Loss Bridge as discussed here:https://www.olymega.org/forum/viewtopic.php?f=60&t=354&sid=5fc663a5ace2163bd5d87bbf6760b400
I guess I got an earlier deal that included the parts for the noise source. The current models have the places on the PCB for them with most of the parts installed. From their ad:
FREE BONUS: We had space left on the PCB, so rather than waste it we have added a noise source circuit at no additional cost. We have even populated most of the components for you. We have the SMA connector required to complete this bonus noise source circuit available for a small additional fee. Details of the noise source circuit are available with the project documentation.
As I recall, all surface mount parts are installed. I think it was just the SMA connector and a jumper that had to be soldered in.
Fortunately, it is open source:https://github.com/opendous/Upconverter1v3
Nooelec 0.5ppm upgraded RTL-SDR on Amazon for $21:http://amzn.to/2npR346
Nooelec Ham It Up 1.3 converter board, extends frequency coverage down to 100kHz. Uses a 125MHz conversion frequency so it no longer ends up in the middle of the FM radio band. . $45http://amzn.to/2nBHkXK
Blue aluminum case for the Ham It Up 1.3. If you add the noise source, you'll need to drill one additional hole for the SMA connector, and if you wish to be able to turn it on and off, another for a switch.http://amzn.to/2lXLYTk