Could the Icom AH-705 be used as a permanently-mounted remote ATU? Sure, but I believe there are better options.

Icom uses this photo to demonstrate one of the ways the AH-705 ATU can be mounted for remote operation.

Many thanks to Bruce (W0MBT) who writes:

Hey Thomas,

After many years of inactivity, the combo of this blog, the IC-705, and Covid shutting down all the other fun things I like to do has finally got me somewhat active again. I agree with you that [the Icom AH-705] seems pretty large and expensive for a portable tuner, given the available alternatives. To me, the most interesting possible application is in a semi-permanent outdoor installation.

Currently, my setup is an EmTech ZM-2 installed in a watertight toolbox on my fifth floor balcony, grounded into the metal siding of my building, with a stealth radiating wire tossed onto a conveniently-located tree. It seems to get out pretty well, but QSYing across bands is a pain, and not really practical when it’s raining, which happens a lot in Seattle. I could replace that whole setup with an AH-705 stuck to the siding with double-sided tape.

My questions (and I realize you won’t yet have answers) are:

* How long will it run on AAs? This will determine whether I need to run 12V out to my balcony.
* What’s the maximum control cable run? In my current apartment layout, I’m looking at about 25′.


Hi, Bruce,

First of all, I’m so glad to hear you’ve gotten back on the air and honored to hear this blog might have contributed to that a bit! Based on your current setup, it’s obvious that you’ll go out of your way to play radio. Anyone who’s willing to manually adjust a remote ATU each time they wish to hop around the band is dedicated to their radio play!

Since the AH-705 hasn’t been released yet at time of posting, I really know nothing about the AH-705 other than what I’ve read in the specs. I’m not sure how long a control cable could be nor how long AA batteries would last. We won’t know this until the AH-705 is tested.

If I were in your shoes, though, I wouldn’t wait on the AH-705.

I can think of  at least two other options I consider to be better choices for a permanently-mounted remote antenna tuners:

1.) Assemble a remote tuner box

So at my QTH, like yours, I rely on an external, remotely controlled ATU. My shack is located on the first floor of my house. There’s a carport with a metal roof behind my shack. Since we designed and built this house. we installed conduit in the walls so that I could run cable from my shack to an antenna switching and tuning point mounted outside.

It’s built around an LDG Z11 Pro which is not marketed as a remote ATU. The Z11 Pro is mounted in a (rather ugly but effective) weather-proof box a friend gave me–I think the box was originally  used in a remote sensing application. It actually has some penetration points on the side I was able to use.

In 2011, when I installed this ATU, I found an old sealed lead acid battery to power the Z11 Pro knowing the Z11 actually requires very little in terms of power. I had planned to bring the battery indoors and occasionally recharge it, but I also happened to have a 5 watt solar panel and Micro M+ charge controller, so I put them to use charging the remote ATU battery.

From inside my shack, I bypass all internal ATUs in my transceivers and only use my remote Z11 Pro.

The Z11 Pro is RF-Sensing, so as I move across the band, it automatically finds matches and keeps the SWR well within an acceptable range (I monitor it indoors with an SWR and Power meter, of course).

This entire system costs less than the $350 projected cost of the AH-705 and doesn’t require a control cable. The best part is it can be used with *any* radio and can handle 125 watts.

I used the Z11 Pro because I already owned it, but there are less expensive, smaller LDG tuners that could be used. You wouldn’t need to have solar charging as you could simply replace an external battery from time to time. These tuners are super efficient–so efficient, the sealed lead acid battery I installed in 2011 was nearly dead back then, yet it has provided enough voltage via my small PV panel to reliably power the Z11 Pro over 10 years of seasonal temperature swings.

But there’s still an easier and possibly cheaper solution.

2.) Buy a proper remote ATU

When I originally built my remote tuning system, there were really no affordable options commercially available. I believe SGC and Icom had remote tuners but they were very pricey.

Since then, LDG introduced the RT100 remote antenna tuner.

The RT100 costs $250 US and is designed to be used outdoors permanently-mounted. You need no outdoor power source because the ATU is powered from a Bias T 12V source via the same coax cable between your transceiver and the ATU. Makes for a neat, tidy package outdoors.

Again, this ATU–unlike the AH-705–can handle up to 125 watts and work with any transceiver in your shack.

Indeed, I’ve been thinking about grabbing an RT100 for use with another outdoor antenna I plan to build!

Also check out the MFJ-926B for $330 US. If you’re like me, you may never operate north of 10-20 watts, but some may appreciate the 200 watt power handling of the MFJ.


To get back to your original question, I suppose what I’m trying to say here is the Icom AH-705 is a portable antenna tuner that can be put into service as a remote antenna tuner. It can do both jobs.

To me, though, it makes more sense to split these two applications: install a permanent remote ATU–that works with any transceiver–and also invest in a quality portable ATU for field work.

What are the major drawbacks of the AH-705 compared with a proper, dedicated remote ATU?

  • You’ll need to change AA batteries in the AH-705 on occasion or design a 12V source that can easily be recharged.
  • The AH-705 may (we don’t know yet) only work with the IC-705 and possibly similar Icom models. The LDG and MFJ ATU models above work with any radio.
  • The maximum power handling of the AH-705 is 10 watts–if you use other transceivers (if that is even possible) you’ll have to be extremely careful of your power settings, else fry the AH-705.
  • The AH-705 is pricey if the actual retail price ends up being near the projected $350 mark. Hopefully, it’ll be less than this.
  • The AH-705 will require a control cable. The options above are RF-sensing and do not.

My advice?

Build or buy a permanent remote tuner and hit the parks and summits with the ZM-2!

Since you already have the Emtech ZM-2, you’ve got a fabulous manual portable ATU. I use my ZM-2 in the field all the time (see photo above). Some folks prefer an automatic tuner for ease of use, but I’m guessing at this point, you’re an expert ZM-2 “tuner upper!”

Later, if you want to add an automatic portable ATU to your field kit, consider the Elecraft T1, the Icom AH-705, or an LDG model.

Readers, feel free to comment with your suggestions as well. I’m sure there are a number of options I haven’t considered!

2 thoughts on “Could the Icom AH-705 be used as a permanently-mounted remote ATU? Sure, but I believe there are better options.”

  1. Hi Thomas,

    Thanks for responding in such detail. I think I was vaguely aware that the RT-100 existed, but for whatever reason, it didn’t occur to me that it would work for QRP. Looking at the manual, I see it should work down to .1 W, so that’s great! Avoiding the need for control and power wires is compelling.

    The manual does say that a balun is “required” for longwire antennas. I wonder why they say that? I understand why it’s needed to feed balanced line, but I’ve never needed a balun for wire antennas…

    Now I just need to figure out a good portable setup!


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