Dipl.Ing. Klaus Bemmerer AT- 615B Short Form Manual

1.5 kW Automatic Remote Controlled
Balanced Antenna Tuner

Model AT- 615B

Short Form Manual

10/2010

Dipl.Ing. Klaus Bemmerer
RF Communication Electronics
Niendorf-Middeldor 11
23769 Fehmarn
GERMANY
Phone [phone]
Fax [phone]

www.hamware.de

eMail: [e-mail]

Antenna Tuner System AT-615B Description

This tuner is designed to match remotely, balanced HF antennas. This unit features
automatic selection of tuner settings based upon transmitted frequency. Unique to this
tuner, no special cabling or adapters are required. The operator simply transmits into the
antenna and the tuner detects the transmitted frequency and selects the correct settings
from memory. The Ham bands are divided into 85 operator programmable memory
locations. It will handle 1500 watts of SSB or CW power, and it can be used in either
automatic or manual mode.

The matching circuit consists of a remotely tuned balanced π circuit. The balun is placed
at the input of the tuner. The Output capacitor is a stepper motor controlled High Voltage
variable capacitor.

The Control Cabinet contains the tuning controls, memory location selection, Automatic or
Manual switching and a display that indicates the memory location in use, the frequency
range as well as the span, and the tuner settings.

Tuner System Block Diagram

Transceiver

SWR Meter

Control Cable

Coax 50 Ohm

AT-615B Automatic
Controller

HF-Sensor

RF Probe

AT-615B
Tuner

Antenna

max. 40m (120 ft)

RF Outdoor
Unit

Power Amplifier

Steuerung Endstufe

Key Line

max. length 15 cm

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Controller Unit:

Antenna matches are stored into a bank of 85 memory locations. Each memory location is
a fraction of an amateur band. Refer to the technical section for the fractional segments for
each band. As shown in the picture below, the upper line of the LCD shows the actual
memory location chosen (lower edge frequency 1840 kHz) with its span (20 kHz). The
control settings for this frequency are shown in the lower line of the LCD. In the Automatic
Mode the memory location and its stored settings is selected by the transmitted input
frequency. The input frequency is obtained from an RF probe. The memory location
contents can be erased by a push button on the back of the controller.

The controller contains 3 rotary encoders that control the tuner elements TRX, L, and ANT.
TRX controls the Input Capacitance, L controls the Inductance and ANT the output
capacitance values. The lower line on the display shows these values.

A manual selector switch is provided for memory selection in the Manual mode.

Controller Unit

LED is lighted when
Power Supply operates
and Power Switch is off

Power Switch

L values switchable in 31
steps.

Never switch with full
poser! Max. switching

power 300W

Control of the variable
output capacitor. 1 step
corresponds to 0.9° tuning
angel. Max. 200 steps

Memory: Read out of the stored settings in
either automatic or manual mode.
Tune: Matching the antenna with the rotary
switches Input, L and ANT
Mem In: By pressing this momentary switch
down the indicated control settings are
stored into memor

y

Input Capacitors
switchable in 256 steps,
17pF each. Steps appear
upon LC Display following
“Txxx”

In „Manual“ mode all
memory locations can be
selected

LC Display
The upper row shows the
actual memory location
(lower edge frequency
with the span)
The lower row shows the
actual control settings for
the antenna

Mode switch
„Manual“ or
„Automatic“
or “Thru”

Yellow LED lights, as long
as tuning proceeds. Don’t
key the transmitter during
this time

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Controller Connections (Rear Side)

RF Probe

25-pin. Control Cable
to Tuner Unit

Power Supply

If the Memory Erase Button is pressed, all
memory locations associated with the band
indicated on the LC Display will be erased

Cinch-Connectors to
loop-in the key line of
Power Amp

RF Probe Installation

Probe Connector to
Controller AT-615

The connection to
the Transceiver
should made as
short as possible.

To Power
Amplifier

RF Probe

If possible, the RF Probe should be attached directly to the antenna jack of the transceiver
using an adaptor or a very short cable.

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RF Unit:

The RF Unit is contained in a weather-protected cabinet (IP66) and is UV resistant. There
are two feed-thru insulators to connect to the antenna elements. The coaxial cable and the
control cable are connected via a N and a 25 pin connectors. There is no active circuitry
inside the RF Unit. This is to insure reliable operation even under non-matched condition.

The LC network is known as Balanced PI. At the front end of the network there is a balun
transformer that matches the unsymmetrical coax cable to the symmetrical tuner elements.
This is the only place where the impedance of the system is purely resistive (when
matched) and is the ideal place for the Balun. The regular station SWR meter (or the built­in meter in the TRX) is used as an indicator to match the antenna.

The capacitors at front end are switched in 256 steps of 17 pF per step. The capacitor at
antenna side is a variable capacitor of 400 pF. The control of this capacitor is by a stepper
motor with 0.9° per step. The inductive paths between the capacitors are switched in 31
steps from 0.2 µH to 35 µH. Switching is done by power relays. With the circuit
components used it is possible to match short antennas up to an unlimited antenna length
within the RF range from 1.8 to 30 MHz.

.

Interior view of the RF unit looking at the capacitor board, the inductor board is located below

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