Here are some rfm69 sensitivity measurements for various rxbw settings.
//---------------------------- bw meas results -----------------------------------------
// 0.125%, dcc = 625 hz, rbw = 500khz, mds = -107dbm with LNA sensboost 8/27/13
// 4%, dcc= 5 khz, lpLabs default rbw=125khz, mds = -109dbm no LNA sensboost
// 0.125%, dcc= 156 hz, lpLabs updated, rbw=125khz, mds = -113dbm with LNA sensboost
// 0.125%, dcc= 62.5 hz, rbw = 50khz, mds = -114dbm
// 1%, dcc = 250 hz, rbw = 25kHz, mds = -117dbm, LNA On 12/08/13
// 1%, dcc= 52 hz, rbw = 5.2khz, mds = -122dbm
// 2%, dcc= 52 hz, rbw = 2.6khz, mds = -123dbm, (best if fcut > 60hz), LNA on. checked agn 12/07
*/
*mds is the weakest detectable signal