I've got a
RTL-SDR.com dongle and a Nooelec Upconverter attached to a 43 foot vertical and the reception is fantastic with the exception of longwave. Have been using this setup for several years. When below 30 MHz it's important to adjust the RF gain otherwise it's all radio hash due to overload. When on HF, first tune to a portion of the band with the gain setting at minimum, then slowly increase the gain until signals are heard. Same goes when listening to VHF/UHF but in my case I have to crank up the gain quite a bit to hear distant stations. For that portion of the band I use a discone. But FM broadcast interference occurs in portions of those bands.
If you are using the Nooelec Upconverter be sure to use a power supply that does not cause interference. I use a 5 volt PocketJuice supply. Also make sure that your Nooelec Upconverter's toggle switch is in the correct position, not in the "Bypass" position. Hope this helps