Icom AH-4 User Manual

3. Inside the AH-4!
I use the AH-4 primarily to feed balanced antennas. I’ve modeled a number of antennas using EZNEC
and I never seem to have good luck when the antennas are unbalanced. An example of an unbalanced
antenna is a long wire connected to the RF out port and the ground connected to, well, ground. I
much prefer feeding either a loop, with the AH-4 right at the feed point, or a flat top via ladder line. In
both these cases the AH-4 works extremely well.!
This is a photograph of my AH-4. It is feeding a 30 meter flat top. The antenna is about 20 meters high
and is fed with 450 ohm ladder line.!
Note that the RF output is on top and the RF ground is on the bottom. I’m not sure why they did this. It
makes one believe that the tuner cannot work with a balanced feed. Nothing could be further from the
truth. It works great. Note that the metal mounting brackets are not grounded.!
FIGURE 2: AH-4 IN OPERATION CONNECTED TO BALANCED ANTENNA!
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