Yaesu FT-901DM Maintenance Service Manual page 20

MOBILE INSTALLATION
(Note: The DC-DC converter described herein is
built-in on the FT-901DM, and is an available
option on the FT-901D/SD/DE models)
The FT-901DM will operate satisfactorily from
any 13.5 Volt DC negative-ground battery source
by connecting the DC power cord to the rear
panel receptacle. For under-dash mounting, a
special mobile mounting bracket is available from
your dealer. In mobile installations the trans-
ceiver should be suited away from heater ducts.
No special precautions need be observed if ade-
quate ventilation space is available. A minimum
of two inches of air space above the cabinet top
and on all sides is recommended to allow proper
air flow around the cabinet. Never stack other
units above or below the transceiver since the
accumulated heat from both units could cause
damage.
The transceiver requires an average of 14 amps
on transmit, with 20 amps on voice peaks. The
DC power cable comes equipped with a 20 amp
fuse. When making connections to the car battery,
be absolutely certain that the RED lead is con-
nected to the positive (+) terminal and the BLACK
lead is connected to the negative (—) terminal.
Reversed connections could permanently damage
the transceiver.
The BLACK lead should, preferably. run directly
to the negative terminal of the battery. Using the
car frame as a negative connection
or connecting
the RED lead to a positive point such as the ig-
nition switch
places the transceiver
in the same
current path as noise-creating devices, thus failing
to take advantage
of the filtering action of the
battery. The power cable should be kept away
from
ignition
wires and should
be as short
as
Possible to minimize voltage drop and to provide
a low
impedance
path from
the transceiver
to
the battery.
GENERAI
ANTENNA CONSIDERATIONS
If an open-wire feedline is used, or if the input
impedance of the antenna system presents a very
high or very low impedance at the coaxial input,
some sort of antenna tuner must be used to pro-
vide a SO - 75 Ohm unbalanced feedpoint for the
transceiver.
For mobile operation, most of the commercially-
available antennas on the market will provide
good results if care is taken to tune the antenna
for minimum SWR. The outer conductor of the
coaxial cable should be securely grounded to the
automobile chassis at the antenna mount.