Yaesu FT-100D Operating Manual page 66

Active·Tuning Antenna System (ATAS·100) Operation
ATAS-100 OPERATING TIPS
The information below will help you derive the best performance possible from the ATAS-
100 Active-Tuning Antenna System.
GROUNDING
It is critically important that you establish a good mechanical and RF ground connection
for your ATAS-I 00 (as with all vertical antennas). Mobile mounts which are bolted through
the vehicle's roof, or otherwise mechanically affixed, will usually be satisfactory. How-
ever, magnetic mounts do not provide the RF grounding necessary for good performance,
and are not recommended for use with this antenna.
TUNING PROCEDURE
The feedpoint impedance of the ATAS-IOO (resistance 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-I 00 to travel
(inward or outward) for best SWR.
To resolve this situation, the transceiver will then command the ATAS-IOO to retract fully
to its minimum height, and thence restart the tuning process. In this instance, the "TUN"
icon will remain on the display after you press the [B](TUN) key. If this happens, do not
press the [B](TUN) key repeatedly. The transceiver will remain in the receive mode as it
retracts (this may take up to one minute). Thereafter, the transmitter will be engaged, and
the ATAS-IOO will be automatically adjusted for best SWR. The "TUN" icon will then
disappear from the LCD, and you will be ready for operation.
The command which retracts the ATAS-I 00 to its minimum height utilizes a fixed timer. If
the ATAS-I 00 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-I
~O's
retraction mecha-
nism includes a clutch assembly to prevent damage to the antenna or motor.
EXTERNAL WATTMETERS
If you wish to use an external wattmeter in conjunction with the transceiver and your
ATAS-IOO, please check the wattmeter with an Ohmmeter prior to installation. Be sure
there is a direct connection between the "IN" and "OUT" jacks of the wattmeter (zero resis-
tance), and also ensure that there is a completely open circuit between the center pin and
shield of the wattmeter's output jack. Some wattmeters use a coil or other device which
shorts the center pin to ground at DC, and this type of internal wattmeter circuitry will not
allow the tuning function of the AT AS-I 00 to operate.
64 FT-100
MICRO MOBILE OPERATING MANUAL