Interference Rejection; Att ( Attenuator ) - Yaesu FT-991A Operating Manual

When the desired signal is extremely strong or the noise level is high on a low frequency band, activate the attenuator to
reduce the incoming signal from the antenna.
1. Press the F ( M-LIST ) button, then touch [ ATT ] on
the LCD. The "ATT" indicator will appear in the
DSP display.
Advice:
 The incoming signal level is reduced by 12dB
( Signal voltage is reduced to 1/4 compared to OFF ) .
Displays ATT
2. To restore full signal strength through the Attenuator
circuit, touch [ ATT ] on the LCD to return the ATT
display to the "OFF" position.
Advice:
If the noise level is high or the received signal is extremely strong, the incoming signal level can be suppressed with the
IPO/ATT settings.
If the S-meter fluctuates S-3 or more in the noise level, or the received signal is extremely strong and it causes a high S-
meter indication ( +20dB or more ) , activate the attenuator.
Since IPO does not only attenuate the incoming signal, but also improves the cross modulation characteristic, try to ac-
tivate the IPO first. If the signal is still strong, also use the ATT. In this way, you can attenuate the incoming signal and
noise effectively.
FT- 991 Operating Manual

Interference Rejection

ATT ( Attenuator )

F ( M-LIST ) Button
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