Welcome to this highly specialized corner of the hobby, Scott.Unfortunately, Mike is exactly right...there are apparently no 1750 meter LowFER beacons on the air right now that can be copied east of the Rockies. EAR from Ontario is a worthwhile target in your vicinity most summers, but is off this year due to antenna damage.
Your best bet for honing LF reception skills right now is probably on the longwave ham bands (2200 and 630 meters), and the remaining aerobeacon NDB stations between those frequency ranges.
As for hardware, RTL SDRs are not your best bet for sensitivity or spurious signal rejection, or even frequency stability in some cases. But they can sometimes be useful, within their limitations.
Probably the biggest factor in lack of sensitivity, though, is the loop-on-ground antenna. They respond almost exclusively to horizontally polarized waves. That's fie at HF, where propagating EM waves arrive with a healthy mix of polarizations, regardless of the transmit antenna orientation. However, the lower one goes in frequency, it becomes nearly impossible to propagate a horizontally polarized wave near the surface of the ground. Thus, a vertical (active or impedance-matched) whip or a vertical loop will be more productive at LF.
John