70
FT-857 Operating Manual
ATAS-100/-120 Operating Tips
The information below will help you derive the best performance possible from the
ATAS-
100/-120
Active-Tuning Antenna System.
Grounding
It is critically important that you establish a good mechanical and RF ground connection for
your
ATAS-100/-120
(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 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-100/-120
(resistance and reactance) will necessarily
vary over a wide range when you change bands. Occasionally, the transceiver’s micropro-
cessor will not initially be able to determine the proper direction for the
ATAS-100/-120
to
travel (inward or outward) for best SWR.
To resolve this situation, the transceiver will then command the
ATAS-100/-120
to retract
fully to its minimum or maxmum height, and thence restart the tuning process. In this in-
stance, the “
WAIT
” icon will remain on the display after you press the [
A
](
TUNE
) key. If this
happens, do not press the [
A
](
TUNE
) 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-100/-120
will be automatically adjusted for best SWR. The
“
TUNE
” icon will then disappear from the LCD, and you will be ready for operation.
External Wattmeters
If you wish to use an external wattmeter in conjunction with the transceiver and your
ATAS-
100/-120
, 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 resistance),
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
ATAS-100/-120
to operate.
Operation on 30/17/12 Meters
Although the
ATAS-100/-120
is not specified for operation on the above bands, and opti-
mum operation is therefore not guaranteed, the
ATAS-100/-120
generally can be tuned
successfully on these bands (some manual adjustment may be required). Operation of the
ATAS-100/-120
on these bands will not damage the antenna’s components; please feel free
to experiment on these bands, if you like.
T
RANSMITTER
O
PERATION
A
CTIVE
-T
UNING
A
NTENNA
S
YSTEM
(
ATAS-100/-120
)
O
PERATION
