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M3SR Series 4100
3.7.2.22
Starting ATU Tuning
Softkey
Operating Manual 6175.4760.02 – 01
Softkey Type
Initiates ATU tuning on current Tx frequency.
During tuning the following status is dis-
played:
If tuning is aborted, the following status is dis-
played:
If tuning failed, the following status is dis-
played:
Starting ATU Tuning
Description
Press 'ATU Tune' softkey to initiate tuning pro-
cess.
The ATU starts tuning to the current Tx fre-
quency.
Usually, shortwave antennas have impedanc-
es far away from 50 ohms, the optimum load
impedance of the power amplifier (PA) or the
input impedance of the receiver.
The task of the antenna tuning unit (ATU) is to
match the antenna impedance to the required
load impedance of 50 ohms.
This matching or 'tuning' can be performed by
either pressing 'ATU Tune', or more easily by
pressing the softkey 'ATU LEARN' in the Fixed
Frequency configuration menu, where the
matching of entire bands can be 'learned' in a
block.
If the band of interest was learned, it is not
longer needed to press ATU Tune after every
frequency change.
Please note, that ATU tuning and ATU learn-
ing result in RF radiation equivalent to approx-
imately 15 W output power.
For best results, avoid co-located transmitter
lines to transmit during ATU tuning.
Do not switch off the R&S GB4000C while
ATU tuning is in progress. Otherwise tun-
ing will be impeded when the
R&S GB4000C is switched on again.
In case of a 'Tuned failed' indication please try
to tune once again or check the antenna instal-
lation and the RF cable between PA and ATU.
3.159
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