27835 AM is an interesting one. Usually when I hear AM signals (English speaking stations) they tend to stay below channel 1 (26965 kHz), with the big exception being truckers, hunters and poachers operating all over the bands.
For what it's worth, 27835 kHz / 27.835 MHz is channel 38 up one band (27385 + 450 = 27835). Maybe they were having a QSO on 27385 and the QRM got too bad so they flipped that band switch.