ICOM AH-705 QST Reivew

Mark J. Wilson, K1RO, [e-mail]

Product Review

Two Autotuners for the
Icom IC-705: The Icom AH-705
and the MAT-TUNER mAT-705Plus

Reviewed by Phil Salas AD5X

[e-mail]

While it is often convenient to have resonant,
matched antennas at your home station, this is often
not the case when operating portable. The IC-705
low-power portable transceiver (reviewed in the Feb­ruary 2021 issue of QST) doesn’t have an internal

antenna tuner, but there are several compact manual
and automatic tuners that can be used with this radio.

In this review, we will look at two autotuners that are
made specifically to interface with the IC-705 via its
tuner interface, which has connections for Start,
Ground, and Key. The Icom AH-705 and the
MAT-TUNER mAT-705Plus both cover 160 through
6 meters and are controlled directly from the IC-705.

42 September 2021 QST www.arrl.org

Reprinted with permission; copyright ARRL.

Table 2
Icom AH-705 Automatic Antenna Tuner

Manufacturer’s Specifi cations

Frequency range: 1.8 – 54 MHz (>98.4-foot antenna),

3.5 – 54 MHz (>23-foot antenna).
Maximum input power: 10 W.
Tuning power required: 5 – 10 W.
Tuning time: Average 2 – 3 seconds, maximum 15 seconds.
Power supply requirement: Two AA cells or 13.8 V dc ±15%.
Current drain: Less than 300 mA (while tuning); less than 1 mA (standby).
Tuning accuracy: Less than 2:1 VSWR.
Number of tuned memories: 45.
Dimensions (height, width, depth): 1.6 × 4.1 × 7.5 inches.
Weight: 15.8 ounces without batteries.

AH-705 Resistive Load and Loss Testing

Untuned Load Power Loss (%) and Tuned SWR by Band (meters)
SWR () 160 80 40 20 10 6

10:1 5.0 16% 16% 16% <3% <3% <3%

1.3 1.3 1.2 1.3 1.3 1.3

8:1 6.25 12% 12% 12% <3% <3% <3%

1.2 1.2 1.2 1.2 1.1 1.3

4:1 12.5 6% 6% 6% 6% <3% <3%

1.1 1.2 1.2 1.2 1.1 1.6

2:1 25 4% <3% <3% <3% <3% <3%

1.1 1.3 1.3 1.1 1.1 1.6

1:1 50 <1% <1% <1% 1% 1% <1%

1.0 1.0 1.0 1.0 1.0 1.0

2:1 100 <3% <3% <3% <3% <3% <3%

1.2 1.2 1.2 1.1 1.0 1.3

4:1 200 8% 6% 5% <3% <3% 6%

1.2 1.3 1.3 1.3 1.1 1.5

8:1 400 8% 6% 5% 4% <3% NT

1.1 1.3 1.3 1.2 1.1 —

10:1 500 11% <3% <3% <3% 8% NT

1.4 1.3 1.2 1.1 1.3 —

NT = no tuning solution found

Figure 2 — One end of the Icom AH-705 has a
BNC jack for RF from the transceiver, a jack for con­trol signals from the transceiver, and an external dc
power connector. The control and power jacks are
protected by rubber covers when not in use.

Figure 3 — The other end of the AH-705 has an
SO-239 jack for the antenna feed line and a binding
post for ground.

Icom AH-705

The Icom AH-705 is housed in a weather-resistant
case. It is powered by two internal AA batteries, or it
can be powered from an external 13.8 V dc power
supply. The AH-705 comes with a 6.6-foot BNC-to­BNC coaxial cable, a 6.6-foot control cable, a
mounting bracket for attaching the tuner directly to an
antenna or other structure, and a dc power plug.
Table 2 lists the AH-705 specifications.

The AH-705 is fairly large, and the IC-705 could sit
right on top of it. The input side of the AH-705 has a
BNC connector, a 3.5-millimeter control cable con­nector, and a 2.1 × 5.5 millimeter coaxial connector
for external dc power. The control and dc connectors
are covered by water-resistant flaps. The output side
of the AH-705 has an SO-239 connector and a
ground lug with a wing nut (see Figures 2 and 3).
The two AA batteries are easily accessible under a
cover on the bottom side of the unit, and no special
tools are required to change batteries. There are no
indicators on the AH-705.

Reprinted with permission; copyright ARRL.

Basic Testing

Standard ARRL resistive load and loss testing was
performed on the AH-705. The results are given in
Table 2. Open/short testing was also performed. Ide­ally, a tuner should not be able to match an open or
short circuit. However, many antenna tuners can tune
into their own internal losses on some bands. As
shown in Table 3, matches were found on some
bands. See my article, “Antenna Tuner Loss Mea­surements,” in the March/April 2021 issue of QEX
for more information.

Using the AH-705

Most operators will probably use the internal AA bat­teries for powering the tuner. This minimizes required
equipment in the field, as the AH-705 cannot be pow­ered from the IC-705. While the AH-705 draws up to
300 mA during tuning, latching relays are used so
that when tuning completes, the AH-705 draws very
little current. As noted in the manual, when the
AH-705 will not be used for a while, the control cable
should be disconnected from the tuner to prevent

www.arrl.org QST September 2021 43