The Icom AH-4 Automatic Antenna Calibrator is designed to work with some of ICOM's amateur radio HF transceivers. It provides reliable frequency matching from 3.5 to 54 MHz when using a cable that is at least 23 feet (7 m) in length. It can also be used to calibrate from 7 to 54 MHz when used with the optional ICOM AH-2b antenna element. The built-in 8-bit microprocessor selects the lower SWR condition from more than 1,040,000 different LC (coil / capacitance) combinations. LC combinations of 45 frequencies previously used are automatically memorized by the AH-4. Once a frequency is memorized, the AH-4 will tune this frequency in less than one second. (The memories are retained only when the power is turned on).

The AH-4 is sealed in a weatherproof plastic housing for convenient outdoor mounting under your antenna. The transceiver and AH-4 tuner must be grounded. Use a short gauge wire or a strap for this. This tuner can be attached to a pole using the two U-bolts provided, or on a flat surface (screws and bolts are provided). The AH-4 comes with a 16-foot (5m) control cable that connects to the rear panel of the compatible ICOM transceiver. A 16-foot (5 m) raw coaxial cable and two PL-259s are provided to connect the antenna output of the transceiver to the input of the AH-4 antenna. PL-259 must be welded by the user.

This calibrator requires about 10 watts (5-15 watts) to activate and can handle up to 120 watts. It operates on 13.8 VDC (less than 2 amps) from the transceiver control cable. Size: 7 x 2.9 x 9.2 inches 2.65 Lbs. (172 x 70 x 230 mm 1.2 kg).