User manual TECHNICS SC-EH500

[. . . ] It will tune dipoles, verticals, Yagis or virtually any coax-fed antenna. LDG pioneered the automatic, wide-range switched-L tuner in 1995. From its laboratories near our Nation's Capital, LDG continues to define the state of the art in this field with innovative automatic tuners and related products for every amateur need. IMPORTANT TUNER SAFETY WARNINGS Like all high power antenna tuners, your AT-1000Pro handles a great deal of RF energy. Very large RF currents flow through the tuner, and very high RF voltages are sometimes present. [. . . ] The LED will come on after 0. 5 seconds to indicate a memory tune. If the Tune button is held longer than 3 seconds, the Tune LED will go off and a full tune will begin when the Tune button is released. Ant 1: Press the Ant 1 button to toggle between Ant 1 and Ant 2. The Ant 1 LED will be on for Ant 1 and off for Ant 2. When you change antennas, the tuner references the last frequency used on that antenna, and recalls tuning settings for that frequency, if any. When the tuner is off (or if DC power is removed), the antenna selection defaults to the Ant 2 position. Cap Up: The C Up button adds capacitance; holding the button down auto-repeats the add. The LED blinks when you reach the upper capacitance limit. Cap Dn: The C Dn button subtracts capacitance; holding the button down auto-repeats the subtract. The LED blinks when you reach the lower capacitance limit. After tuning is completed, set your amplifier to operate, key your exciter and tune your amplifier as usual (if needed). Error Indications The LEDs may indicate several error and status states: Power too low: your AT-1000Pro requires at least 5 watts to tune. If the power is too low, all LEDs will flash once. Loss of power during tune: if RF power is removed before a tuning cycle has ended, all LEDs will flash twice. Final SWR over 3: in rare cases, your AT-1000Pro will not be able to achieve an SWR lower than 3. This is most often due to attempting to tune very far from the resonant frequency of your antenna, or load up a lawn chair. The resultant tune settings are not stored Power too high: if the power exceeds 125 watts, a tuning cycle will not begin; all LEDs will flash four times In this case, reduce power and begin a new tuning cycle. SWR too high for the power level: if power exceeds 100 Watts while the SWR is greater than 3, or if power exceeds 75 watts while the SWR is greater than 5, a tuning cycle will not begin, and all LEDs will flash five times In this case, reduce power and begin a new tuning cycle. A word about "roll-back" circuits Modern amateur exciters with solid state finals usually employ a "rollback" circuit to protect the final amplifier transistors from high SWR, which can damage or destroy them. A rollback circuit senses the SWR at the antenna terminal during transmit, and reduces the output power as the SWR rises above a preset level, often 2:1. The higher the SWR, the lower the power is set to prevent damage. 11 If your solid state or tube-type exciter has a rollback circuit, you can simply key down and tune as described above at any power level from 5 to 125 watts. If your exciter lacks a rollback circuit, you must manually set the power level for tuning to 30 watts. At higher power levels, the reflected power encountered during the tuning cycle could damage your exciter or tuner. [. . . ] The routine first de-energizes the high/low impedance relay if necessary, and then individually steps through the inductors to find a coarse match. With the best inductor selected, the tuner then steps through the individual capacitors to find the best coarse match. If no match is found, the routine repeats the coarse tuning with the high/low impedance relay energized. The routine then fine tunes the 15 capacitors and inductors. [. . . ]