Antenna Considerations - Yaesu FT-902DM Instruction Manual

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.
Before connecting the power cable to the trans-
ceiver, check the battery voltage with the engine
running (battery charging). If the voltage exceeds
15 Volts DC, the regulator should be readjusted
so that the highest charging rate does not ex-
ceed 15 Volts. The transceiver should always be
switched OFF while the car engine is being started
to prevent voltage transients from damaging power
supply components.
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Width ="
Width = '"'-1"'
Width Control Action
Rejection
Tuning
Action
ANTENNA CONSIDERATIONS
The FT-902 transceivers are designed for operation
using an antenna system presenting a 50-75 ohm
resistive load at the antenna jack. Amateur instal-
lations seldom meet this requirement over the
entire spread of every band, but the final amplifier
pi network is sufficiently forgiving to allow for
minor deviations from the target figure. However,
significant departures from the 50—75 ohm range
will result in seriously degraded transceiver per-
formance.
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 50 - 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.
(LSB Carrier}|
10.76 MHz
x
z
° o
o
o
Cf tol
(ssB) (cw)
SSB, CW SSB
Filters Filter
a
3
— | 4
g 10)-—o =a |
2 ++ | Lt
=- ++
70 'o=eoons ||
ml
Ss Ji J
oF
10°
10
Frequency(Hz)}
APF Action