FlexRadio Systems FLEX-6000 Signature Series User Manual

FLEX-6000 Signature Series - SmartSDR for Windows Software User’s Guide
Page 91
Copyright 2018 FlexRadio Systems. All Rights Reserved.
24 HOW TO OPERATE THE ATU
The antenna tuning unit (ATU) is a device in the RF signal path between the transmitter and its
antenna to improve power transfer between them by transforming the impedance at the antenna
feed output at the transmitter to a value compatible with the transceiver’s power amplifier. An ATU
is useful when the antenna’s feedline impedance is unknown, complex, or otherwise different from
the transceiver. It's important to remember that the ATU has no effect on the actual SWR of the
antenna and feedline. It does however change the impedance presented to the transmitter from the
ATU.
Note that the radio software automatically folds back transmitter power so that the power reflected
by the antenna and tuner system does not exceed 25 watts. This feature protects the Power
Amplifier but should not be relied upon when operating with a mismatched antenna. Use of the ATU
or an external tuner is recommended to match the transmitter to the antenna and minimized power
reflected to the Power Amplifier.
The FLEX-6000 ATU is a standard feature of the FLEX-6500, FLEX-6600/M and FLEX-6700 and an
option for the FLEX-6300 and FLEX-6400/M. The operation of the ATU is controlled by the SmartSDR
software.
24.1 MODES OF OPERATION
There are two modes of ATU operation; manual and memory. In manual mode, the user initiates an
ATU tune operation to attempt find a better match between the PA and the antenna system, but the
inductance (L) and capacitance (C) values are not retained and the ATU will revert to bypass mode if
the frequency or band is changed. Memory mode is an extension to Manual mode where the L/C
values are retained and automatically used when the frequency of the transmit slice is within the
ATU Match Frequency Range (with the same TX antenna selected).
What constitutes a successful ATU match? The ATU will try to impedance match the load to as close
to a 1.1:1 SWR as possible. If the ATU measures an SWR of 1.1:1 or better at the beginning of the
matching process, SmartSDR will leave the ATU in bypass and report Success.
A successful ATU match on 6m occurs when the SWR is improved from the initial SWR determined in
the bypass state and is better than 2.32:1. For non-6m operation, a successful ATU match is one
where the SWR is improved from bypass SWR reading and is better than 1.7:1.
The ATU will stay enabled but the ATU status indicator will not report Success if the SWR improved
from bypass but does not meet the above SWR criteria. If the resulting SWR after an ATU tuning
operation is not better than when in Bypass and the above SWR criteria is not met, the ATU goes into
Bypass (ATU button is not illuminated) and ATU status indicator does not report Success.
ATU Match Frequency Range – After the ATU has found a successful match, the inductance (L) and
capacitance (C) values are valid for a 200 kHz frequency span centered at the frequency the ATU
tuning operation was initiated, or +/- 100 KHz. Once you tune the frequency of the transmit slice
beyond that range, the ATU will be put into Bypass mode. The only exception is if there is another
previously saved ATU memory frequency contained within that ATU Match Frequency Range and you
have ATU memories enabled.

FlexRadio Systems FLEX-6000 Signature Series Specifications

General

Brand	FlexRadio Systems
Model	FLEX-6000 Signature Series
Category	Transceiver
Language	English