Page 62
FT-991 OperaTing Manual
About Atu operAtion
Figure 1 depicts a situation where normal tuning via the ATU has been successfully completed, and the tuning data has
been stored in the ATU memory. The antenna system as seen by the transmitter is shown.
In Figure 2, the operator has changed frequency, and the “
HI-SWR
” icon has appeared. The operator presses and holds
in the
TUNE
button for one second to begin impedance matching using the ATU.
If a high SWR condition exists (above 3:1), corrective action must be taken in the antenna system to bring the imped-
ance closer to 50 Ohms. The ATU will refuse to memorize settings on frequencies where the SWR exceeds 3:1. A High
SWR may indicate a mechanical failure in the feed system, and can lead to the generation of spurious signals causing
TVI, etc.
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 memory. If you return 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 memorized. Please investigate
the high SWR condition and resolve the problem before attempting further operation using this antenna.
usinG the autoMatic antenna tuner
Figure 1
Figure 2
Feed Point SWR
SWR: 3.0
Retuned Setting
Memorized ATU Tuning
The “HI-SWR” icon appears on the display
when you transmit on the frequency
SWR after ATU Tuning
Frequency
Frequency
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