As far as I can determine, the radio defaults to the built-in ferrite loop for
broadcast band reception and below. The instruction manual on page 35 shows an
illustration indicating that when listening to MW/LW frequencies, an external
antenna must be coupled to the radio via an induction loop; whereas on SW
frequencies, the external antenna is connected via the external antenna jack or
via clip to the built-in telescoping whip.
Ken Maltz
Jericho, NY
NRD-535D, NRD-220 Collins R-388, Racal RA6790/GM,
ICOM R71A, ICOM R-7100(x3), AOR AR-8000
Panasonic RF-2200, Sony ICF-7600GR,
Hoka Code3 Gold-Pro, 60' long wire, MLB balun