Icom AH-4 User Manual

5. Electrical Interface
The AH-4 uses 12 volt inverted logic and an “open collector” transistor to ground to perform signaling.
The radio provides 13.8 volts to the tuner. It also provides a START line that is pulled up to 13.8 volts
inside the radio. The radio pulls the START line to ground to assert the signal (start the tuning
operation). Similarly, the AH-4 pulls the KEY line to 5 volts through a 22 K ohm resistor/diode
combination. The radio also pulls this line to 13.8 volts through a resistor. The AH-4 pulls this line to
ground to assert the signal (indicate tuning status to the radio.)!
6. Revision History
Revision
Date
Description
2
2019-05-22
Formatting for PDF presentration
1
Original
AH-4 Operation
K9EQ
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Icom AH-4 Specifications

Frequency and Impedance

frequency range with antenna longer than 7 m	3.5–54 MHz
frequency range with AH-2b	7–54 MHz
input impedance	50 Ω

Power

maximum input power	120 W
tuning power required	10 W (5–15 W)
rated voltage	13.8 V DC ±15% (current drain less than 1 A)

Operating Environment

usable temperature range	–10°C to +60°C (+14°F to +140°F)
VSWR	2.0 : 1 or less
dimensions	172(W) × 69.5(H) × 230(D) mm; 6[25]⁄32(W) × 6[3]⁄4(H) × 9[1]⁄16(D) in

Weight and Dimensions

weight	1.2 kg (2.65 lb)
dimensions	172(W) × 69.5(H) × 230(D) mm; 6[25]⁄32(W) × 6[3]⁄4(H) × 9[1]⁄16(D) in