If you buy carefully you can usually get 1800 on a TV Tuner with the right chipset. You can get to 2.4GHz with a satellite downconverter if you haven't by then bought in enough to buy a (way) more expensive SDR.
E400 goes to around 1.7 GHz, R820T to about 1.85 GHz, which doesn't cover the full LTE band, so yes it's pretty shit at the higher frequencies, 10$ won't get you anywhere there.
