He wants lower carrier frequencies, not more receive bandwidth. For example, HF [1] is 3 to 30MHz, and cannot be received by HackRF without an upconverter, which adds another board and another $43 [2] to the equation.
Also, if you want to go all the way down to DC, the upconverter approach doesn't really work.
Also, if you want to go all the way down to DC, the upconverter approach doesn't really work.
[1] http://en.wikipedia.org/wiki/High_frequency [2] http://www.nooelec.com/store/ham-it-up-v1-0-rf-upconverter-f...