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Introduction:
The AT-11MP is a full-featured auto or semi automatic antenna tuner designed for
HF (1.8 to 30 MHz) transceivers using between 5 to 150 watts. The tuner uses a switched “L”
configuration with 256 capacitor, 256 inductor and Hi/Lo-Z settings to provide over one hundred
and thirty thousand tuning combinations. The tuning range is 0 to 3900 pf and 0 to 20 uH. The “L”
network works great with just about any coax fed antenna (dipole, vertical, beam, etc). Users with
long wires can install a balun between the tuner and the antenna. Tuning time is between 0.1 and
6.0 seconds with the average being about 2.5 seconds.
A cross reading dual needle meter will provide an indication of SWR while RF is present and DC
power is on. Since the power is actually calculated in the processor, the meter does not function
with the power off.
Operation
: Connecting the unit to 12 Volts DC will initialize the microprocessor. The unit will draw
a small amount of power even if the main power switch is moved to the standby position. This is to
provide power to the memory circuits that will allow the last tuned position to be recalled. Placing
the Power/Standby switch to the on (up) position will light the red LED and the meter backlighting.
The unit is now ready for operation. Turning the unit off by the front panel Power switch places the
tuner into Standby. During standby, the tuning section is in bypass. Turning the unit back on will
set the tuning section to the settings acquired before being in Standby.
The Auto/Semi switch controls how the tuning process will be envoked. In Auto mode (Auto/Semi
toggle switch in Auto), the tuner will seek a 1.5 match (or better) anytime the SWR rises above
3.0. In Semi mode (Auto/Semi toggle switch in Semi), the tuner will seek a match only when the
Tune push button is pressed. Both modes require that more than 5 watts of RF power be present.
If the Tune button is pressed and there is less than 5 watts of power, both meter needles will
bounce once to indicate that there was not enough RF to tune properly.
