General; Description And Function Of The Tuner - Acom 04AT Operating Manual

1. GENERAL

1.1. DESCRIPTION AND FUNCTION OF THE TUNER

This operating manual covers the installation, operation, and maintenance of the remote
automatic antenna tuner for HF+6m with integrated four way antenna switch model
ACOM 04AT.
The ACOM 04AT tuner is specifically designed and developed to work exclusively with
the ACOM series of transistor amplifiers. It automatically selects one of four available
antenna outputs (as assigned in bands by the operator) and matches the impedance of
the chosen antenna output by transforming it to 50 Ohm with SWR below 1.5:1 at the
tuner input (typically below 1.3), providing an optimum load impedance for the amplifier.
Any necessary readjustments are swift, following the frequency changes and antenna
selections.
The tuner matches all load impedances presenting a SWR below 3:1, regardless of
phase angle, in a continuous frequency range of 1.8 – 30 MHz and 50 – 54 MHz. In
many cases, the tuner will match loads with higher SWR (up to 10:1) as well, however
a reduction in power may be necessary if the protective functions of the tuner activate
due to high values of SWR, current, voltage, forward or reflected power at the antenna
output.
Provided the SWR of the feedline/antenna system is up to 3:1, the tuner can handle input
power levels up to 1200W (PEP, mean or continuous carrier), regardless of the operating
communication mode. For feedline/antenna system SWRs between 3:1 and 10:1, the
maximum permissible power at the tuner input is gradually reduced down to 200W at
SWR=10:1 (Table 8.1), allowing for operation within tuner component specifications.
The tuner can be installed both in the shack and in a remote location, e.g. in a separate
room, in a sheltered location outdoors or even out in the open, close to the antennas,
so that any feedlines from the unit to the antennas, working in mismatched conditions,
are kept as short as practically possible to avoid unnecessary losses.
Generally, a remote installation of the tuner is preferable to a local one, because it
reduces RF losses in most of the feedline's length. Thanks to the built in automatic
antenna switch, a significant reduction in both installation effort and required cable
length can be achieved (up to three times the feedline length with four antennas and
in-shack tuner installation).
A single cable connects the tuner to the radio station – the main coaxial feedline, which
is often already pre-installed. Tuner power supply, control and RF signals are combined
on the feedline, easing remote installation, lowering costs and uncluttering the shack.
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