User manual TECHNICS SC-EH500

[. . . ] It will tune dipoles, verticals, Yagis or virtually any coax-fed antenna. 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. Your AT-1000Pro is designed to safely handle this RF energy within its specifications, with a reasonable margin of safety. [. . . ] A medium press (0. 5 - 3 seconds) begins a memory tune; memories for the current frequency will be scanned for a match. If stored parameters are not found, the tuner will automatically begin full tuning cycle. 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. 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. Cap Dn: The C Dn button subtracts capacitance; holding the button down auto-repeats the subtract. After tuning is completed, set your amplifier to operate, key your exciter and tune your amplifier as usual (if needed). Good practice dictates tuning your amplifier into a 50-ohm dummy load with a suitable power rating. You may tune your amplifier into the antenna through your AT1000Pro providing it has tuned the antenna to a low SWR, and also providing you do not exceed the specified ratings of either your amplifier or your AT-1000Pro. Memory Operation At the end of each successful tuning cycle (SWR <1. 5), the tuning parameters are stored in nonvolatile memory. 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. Check your exciter owner's manual to determine if yours has a rollback circuit. Most solid state radios (except Ten-Tec) have a rollback circuit. LED Error codes Condition Good tune Insufficient or no RF RF lost before tune completed No satisfactory match found RF > 125 watts when Tune req. Meter over scale LED Code Tune LED blinks 5 times All LEDs flash one (1) time All LEDs flash two (2) times All LEDs flash three (3) times All LEDs flash four (4) times All LEDs flash five (5) times Cap and Ind Up/Down LEDs flash Default Setting Values Auto Ant Threshold Scale Power Up On/Off Setting On Ant 1 2. 0 1, 000 On Radio Interface The AT-1000Pro includes interface cables for most Icom and the FT-857 (D) and FT-897(D) radios. The Icom interface will provide DC power to the tuner as well as control the keying of the radio during the tune cycle. The Start line (an input to the tuner) is grounded to start the tuning process. The Key line (an output from the tuner) is grounded for the duration of the tuning cycle. [. . . ] Although the microprocessor's oscillator runs at 20 MHz, its internal bus speed is one-half that, or 10 MHz. The main tuning routine takes about 75 cycles to make a tuner adjustment and take a new SWR measurement, or 67. 5 ms per tuner adjustment. If running at maximum speed, the microprocessor can try all inductor-capacitor combinations in just five seconds. Unfortunately, the mechanical relays can't react as quickly as the microprocessor, and the tuning speed must be slowed down to compensate for relay settling time. [. . . ]