Using The Automatic Antenna Tuner - Yaesu FT-710 Operation Manual

Using the Automatic Antenna Tuner

The Automatic Antenna Tuner (ATU) is built into each FT-710. The ATU is designed to ensure that a 50-
Ohm antenna impedance load is presented to the final amplifier stage of the transmitter.
• Because the FT-710 ATU is located inside transceiver, it can only adjust the impedance presented to the
transceiver end of the coaxial cable feedline. It does not "tune" the SWR at the antenna feed point itself.
When designing and building an antenna system, we recommend that every effort be made to also ensure a
low SWR at the antenna feed point.
• The ATU in the FT-710 is designed to match impedances within the range of 16.5 Ohms to 150 Ohms, cor-
responding to an SWR of 3:1 or less on the HF amateur bands (6 m amateur band: 25 Ohms to 100 Ohms,
corresponding to an SWR of 2:1 or less). Accordingly, simple non-resonant whip antennas, along with ran-
dom-length wires and the "G5RV" antenna (on most bands) may not be within the impedance matching
range of the ATU.
• The built-in antenna tuner cannot be used with an antenna connector connected to an external antenna tuner.
• ATU Operation
1. Press the [TUNE] key momentarily to place
the ATU in the transmit line (no adjustment or
tuning will occur yet).
While the ATU function is activated, the
"TUNE" will be displayed.
● The momentary press of the [TUNE] key
will turn the tuner ON, and the microproces-
sor will automatically select the tuning point
closest to the current operating frequency.
2. Press and hold the [TUNE] key to begin auto-
matic tuning.
● The transmitter will be engaged, and
"TUNE" will be displayed while tuning is in
progress.
● Always listen on the operating frequency
before beginning the tuning process, to be
sure tuning will not interfere with others who
may already be using the frequency.
● When the optimum tuning point has been
achieved, the transceiver will return to re-
ceive.
3. To disengage the ATU from the transmit line,
press the [TUNE] key momentarily.
The ATU microprocessor memories store the
record of the capacitors and inductors select-
ed to tune each 10kHz window in which tuning
has occurred. This eliminates the need to re-
tune every time operation returns to a frequency
on which the tuning process has already been
completed.
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About ATU Memories
SWR (After tuning) Less than 2:1
The tuner settings are stored in the ATU
memory.
SWR (After tuning) Greater than 2:1
Tuning data will not be retained in mem-
ory. If operation is returned to the same
frequency, the tuning process must be re-
peated.
SWR (After tuning) Greater than 3:1
The "HI-SWR" icon will light up, and the
tuner settings, if achieved, will not be mem-
orized. Investigate the high SWR condition
and resolve the problem before attempting
further operation using this antenna.