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The Capacitor and Inductor Up and Down switches are used for fine-tuning the inductors and
capacitors and can be used in either, Auto or Semi mode. Pressing either of the Up switches will
increment that tuning section until it reaches the maximum range. When the maximum value is
reached, both meter needles will bounce. Conversely, pressing either of the Down switches will
decrement that tuning section until it reaches the minimum range. When the minimum value is
reached, both meter needles will bounce.
Pressing both Cap and Ind Down switches at the same time will reset the processor and place all
relays in a bypass position.
Pressing the Tune push button and the Ind Up button will turn on the audio feedback feature (if
installed). Pressing the Tune push button and the Ind Down button will turn off the audio. When an
eight-ohm speaker is connected to J4, an LM386 amplifier is installed at U4 and audio is turned
on, audio feedback will provide an indication of the SWR level. The feedback is a series of one to
five beeps where one beep is an indication of SWR below 1.5, two indicates SWR between 1.5
and 2.0, three indicates SWR between 2.0 and 2.5, four indicates SWR between 2.5 and 3.0, and
five indicates SWR above 3.
The back panel has SO-239s for connecting UHF type connectors to the antenna and transmitter.
A coaxial power jack with center positive is used to provide DC power to the tuner. The jack mates
with a 5.5 OD, 2.5 ID coaxial power plug. Between 11 and 15 volts DC can be used. The power
supply must be able to provide up to 0.5 amps.
On the back panel is the Radio Interface. This works with radios that are compatible with the Icom
AH-4, Alinco EDX-2 and Kenwood AT-50 tuners. When connected to a compatible radio, it
enables the “Tune” button on the radio. Pressing the Tune button on the radio will cause the radio
to temporarily switch modes to CW, transmit 10 watts and start the AT-11MP tuning cycle. Once
the tuning cycle is complete the AT-11MP will signal the radio that the tuning is complete and the
radio will return to the previous mode and power settings. Note that only control signals are used
in the radio interface. Power and ground must still be provided through the AT-11 MP coaxial
power jack. Also be sure to power the AT-11MP on first, then the radio to allow the radio to know
that a remote tuner is present.
Optional cables and interfaces are available for the radios mentioned above. Interfaces for
selected Yaesu radios area available through W4RT Electronics (
www.w4rt.com
).
Operational Notes:
Most tuning situations with the AT-11MP is very straightforward. With the
tuner is the Semi mode, simply transmit a continuous carrier (AM mode is recommended) and
momentarily press the tune button. The tuner will find the best match and stop tuning.
Note that even though the tuner can handle 150 watts, it must be tuned with reduced power. If
your radio has an automatic “foldback” circuit, you will not have to lower the power manually. A
foldback circuit will lower the power of the radio whenever the SWR is high. Typically, most solid
states radios have foldback circuits. Tube radios and most Ten-Tec radios do not lower the power
when the SWR is high. In these cases, the power should be lowered to approximately 25 watts
before tuning is started.
