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FT-450D O
PERATION
M
ANUAL
U
SING
THE
A
UTOMATIC
A
NTENNA
T
UNER
The Automatic Antenna Tuner (hereinafter referred to as the “ATU”) built into each
FT-450D
is designed to
ensure a 50-Ohm load for the final amplifier stage of the transmitter. We recommend that the ATU be used
whenever you operate on the
FT-450D
.
A
DVICE
:
Because the ATU of the
FT-450D
is located inside the station, it only adjusts the impedance presented to the
transceiver at the station end of your coaxial cable feedline. It does not “tune” the SWR at the antenna feed
point itself. When designing and building your antenna system, we recommend that every effort be made to
ensure a low SWR at the antenna feed point.
The ATU of the
FT-450D
includes 100 memories for tuning data. Eleven of these memories are allocated,
one per Amateur band, so that each band has at least one setting preset for use on that band. The remaining
89 memories are reserved for the 89 most-recent tuning points, for quick frequency change without the need
to retune the ATU.
The ATU in the
FT-450D
is designed to match impedances within the range of 16.7 Ohms to 150 Ohms,
corresponding to an SWR of 3:1 or less on the 160 through 6 meter amateur bands. Accordingly, simple
non-resonant whip antennas, along with random-length wires and the “G5RV” antenna (on most bands) may
not be within the impedance matching range of the ATU.
ATU O
PERATION
1. Use the Main Tuning Dial knob to set the radio to
the desired operating frequency within the Ama-
teur band.
2. Press the [TUNE] button momentarily to place
the ATU in the transmit line (no adjustment/tun-
ing will occur yet). The “
” icon will appear
in the display.
Q
UICK
P
OINT
:
The momentary press of the [TUNE] button will
turn the tuner on, and the microprocessor will
automatically select the tuning point closest to
the current operating frequency.
3. Press and hold in the [TUNE] button for one sec-
ond to begin automatic tuning. The transmitter
will be engaged, and the “
” icon will blink
while tuning is in progress. When the optimum
tuning point has been reached, the radio will re-
turn to receive, and the “
” icon will again
glow steadily (instead of blinking).
4. To disconnect the ATU from the transmit line,
press the [TUNE] button momentarily. The
“
” icon will turn off, confirming that the ATU
has been turned off. In the “Off” mode, the trans-
ceiver will be directly connected to the coaxial
cable connected to your antenna, and will oper-
ate based on whatever impedance is present at
the station end of the coax.
A
DVICE
:
The ATU circuit is located between the final amplifier
and the rear-panel antenna jack; reception is not af-
fected by the ATU.
Q
UICK
P
OINTS
:
As shipped from the factory, only one ATU alignment
point is saved on each Amateur band. This was
memorized during the final alignment and perfor-
mance verification stages on the production line.
N
OTE
:
Please check the operating frequency before begin-
ning the tuning process, to be sure you are not inter-
fering with others who may already be using the fre-
quency.
T
ERMINOLOGY
:
Antenna Tuner Memories: The microprocessor of the
ATU makes a note of the positions of the tuning ca-
pacitors and the selected inductors, and stores the
data for each 10 kHz window in which tuning has
occurred. This eliminates the need to re-tune every
time you return to a frequency on which you have
already completed the tuning process.
[
TUNE
] button
