Yaesu FT-847 Operating Manual page 65

A -T
CTIVE UNING
Notes:
m Once automatic matching has been successfully
accomplished, you must change frequency by at
least 10 kHz before attempting automatic match-
ing again. Within a window of ±10 kHz from a
match point, the transceiver's microprocessor will
ignore any command to attempt automatic match-
ing.
m Antenna tuning is accomplished using a "CW" car-
rier, although the mode indication will not change
to "CW" (if you are operating on another mode)
during antenna tuning.
m If you see a "H I S W R " indication on the LCD, it
may mean that there is a problem in your coaxial
cable (bad connection, etc.) which is preventing
The information below will help you derive the best performance possible from your new ATAS-100 Ac-
tive-Tuning Antenna System.
G
ROUNDING
It is critically important that you establish a good
mechanical and RF ground connection for your
ATAS-100 (as with all vertical antennas). Mobile
mounts which are bolted through the vehicle's roof,
or otherwise mechanically affixed, will usually be
satisfactory. However, magnetic mounts do not pro-
vide the RF grounding necessary for good perfor-
mance, and are not recommended for use with this
antenna.
T P
UNING ROCEDURE
The feedpoint impedance of the ATAS-100 (resis-
tance and reactance) will necessarily vary over a
wide range when you change bands. Occasionally,
the transceiver's microprocessor will not initially
be able to determine the proper direction for the
ATAS-100 to travel (inward or outward) for best
SWR.
To resolve this situation, the transceiver will then
command the ATAS-100 to retract fully to its mini-
mum height, and thence restart the tuning process.
In this instance, the "WAIT " icon will appear on
the display after you press the [TUNER] button. If
this happens, do not press the [TUNER] button
repeatedly. The transceiver will remain in the re-
ceive mode as it retracts (this may take up to one
minute). Thereafter, the transmitter will be engaged,
and the ATAS-100 will be automatically adjusted
for best SWR. The "WAIT " icon will then disap-
pear from the LCD, and you will be ready for op-
eration.
FT-847 O
PERATING
A S
NTENNA
ATAS-100 Operating Tips
M
ANUAL
( ATAS-100 ) O
YSTEM
successful tuning. Replace the cable, or try adding
a few feet/meters of cable (to eliminate the possi-
bility of adverse "transformer action" in the 50
cable during the tuning process).
m If you are able to achieve an SWR of less than 2:1
via manual tuning, the FT-847 will "accept" the
manual setting, and you may then re-tune automati-
cally when changing bands.
m If, however, you stop manual tuning at a non-opti-
mum setting (SWR >2:1), the FT-847 will not per-
mit further automatic tuning. To refresh the setting
of the ATAS-100, press the [MH
ATAS-100 will fully retract. You may then restart
automatic tuning per the procedures described ear-
lier.
The command which retracts the ATAS-100 to its
minimum height utilizes a fixed timer. If the ATAS-
100 reaches its minimum height before the timer
has expired, you may observe the antenna's motor
continuing to rotate; this is normal, as the ATAS-
100's retraction mechanism includes a clutch as-
sembly to prevent damage to the antenna or motor.
E W
XTERNAL ATTMETERS
If you wish to use an external wattmeter in con-
junction with the transceiver and your ATAS-100,
please check the wattmeter with an Ohmmeter prior
to installation. Be sure there is a direct connection
between the "I " and "O
N
ter (zero resistance), and also ensure that there is a
completely open circuit between the center pin and
shield of the wattmeter's output jack. Some watt-
meters use a coil or other device which shorts the
center pin to ground at DC, and this type of inter-
nal wattmeter circuitry will not allow the tuning
function of the ATAS-100 to operate.
O
PERATION ON
Although the ATAS-100 is not specified for op-
eration on the above bands, and optimum opera-
tion is therefore not guaranteed, the ATAS-100
generally can be tuned successfully on these bands
(some manual adjustment may be required). Op-
eration of the ATAS-100 on these bands will not
damage the antenna's components; please feel free
to experiment on these bands, if you like.
OPERATION
PERATION
q] key until the
Z
" jacks of the wattme-
UT
30/17/12 M
ETERS
63