Pioneer F-91 Operating Instructions Manual page 4

CONNECTIONS
OUTDOOR AM ANTENNAS
The accessory AM loop antenna is quite sufficient if you live
in a strong-signal area. However, an outdoor AM antenna
should be erected if surrounding objects are interfering with
reception, or if the stations are distant and their signals are weak.
NOTE:
Do not detach the AM loop antenna when using an outdoor
AM antenna.
GROUNDING
Grounding is recommended if reception of FM programs is
impaired by noise. To ground, connect a thick polyvinyl wire
to the GND terminal and attach the other end to a metal water
pipe or grounding bar, or wind it around a copper plate and
bury it.
NOTE:
Never connect a wire to a gas pipe for grounding as there
is the danger of a explosion in case of lightning.
4
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Connecting the outdoor AM antenna
Outdoor AM antenna
AM wire antenna .
(vinyl-insulated wire)
AM loop antenna