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8. TUNER (ATU) – WHERE FITTED
The amplifier has an automatic tuner that handles load mismatches up to 3:1 VSWR
(2.5:1 for 6 m).
The amplifier contains a look-up table with all the permitted bands.
For tuner management, antenna data and other working data are stored.
Every band has a sub-band set, and for each of those, data related to the antenna and
auto-ATU tuning is stored.
The CAT and the frequency counter detect the operating frequency and the correct
sub-band.
Due to the stored data, the tuner and the antenna are automatically set correctly.
As described earlier (see item 4.6), the amplifier has two different memory banks.
It is possible to use the two different presets when the amplifier operates at two different
locations.
Furthermore, table-driven management is useful to inhibit operations of the amplifier.
For example, when an antenna for a particular band is not available.
All auto-tuner functions remain, on standby, while using the transceiver only.
Setting of the match data to write to the tables is performed automatically by pressing
the [TUNE] key. The system will then find the correct match for minimum SWR.
To achieve a better match than that achieved with the automatic tune procedure
( which is rather unlikely) it is possible to set the tuning manually by using the keys
[◄C], [C►], [◄L], [L►].
When a manual tuning is performed, it is possible to read the tuning value, the working
frequency and the associated sub-band on the appropriate screen page.
Both types of tuning are always implemented in the “STANDBY“ state.
Before starting a matching process, the tuner measures the SWR of the system cable /
antenna. if it is greater than 3.5:1, the procedure does not begin and an alarm is
displayed.
It is possible to bypass the tuner with a specific command, in order to use an external
tuner.
NEVER USE THE INTERNAL TUNER WITH AN EXTERNAL TUNER, IT COULD
SERIOUSLY DAMAGE THE LINEAR.
IF YOU WANT TO USE AN EXTERNAL TUNER, THEN DISABLE THE INTERNAL
ATU.
The internal tuner may be bypassed as follows:
- Totally.
- For single band.
- For single band and specific antenna.
It is always automatically bypassed:
- With the only receiving antenna set.
- With tunable antenna set.
- On 70 MHz band.
Note: The tuner, like all analog circuits, introduces a loss (0.8 dB max.) that may vary with
tuning conditions. The power meter of the amplifier does not show this loss as the
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