Icom publishes AH-705 antenna tuner details

Many thanks to Rob Sherwood (NC0B) who notes that Icom has published details regarding their new AH-705 antenna tuner which is designed to pair directly with the Icom IC-705 QRP transceiver.

Many Icom IC-705 owners have been waiting to learn more about the AH-705 before purchasing a dedicated portable ATU for their IC-705. Some of these details may help potential customers make a purchase decision.

Key specifications and features per Icom:

 

  • Covers the 1.8 MHz to 50 MHz bands

30 m, 98.4 ft or longer antenna: 1.8 – 54 MHz, 7 m, 23 ft or longer antenna: 3.5 – 54 MHz
* Depending on operating conditions or environments, the tuner may not be able to tune the antenna.

  • SO-239 antenna connector for 50 Ω antenna such as dipole or Yagi
  • “Terminal connector”, binding post socket adapter supplied for a long wire antenna

  • 2-way power sources using alkaline batteries (2 x AA cells) or external 13.8 V DC*
    * 13.8 V DC should be taken directly from an external power supply, not through the IC-705.
  • IP54 dust-protection and water resistance construction*
    * The connectors should be covered with an adhesive tape or a jack cover to prevent water seeping into the connection.
  • Full automatic tuning, just push the [TUNER] button on the IC-705
  • Latching relays used for saving power consumption
  • 190 × 105 × 40 mm; 7.5 × 4.1 × 1.6 in, 450 g; 15.8 oz* compact design
    * Battery cells are not included.
  • 45 tuner memories

Of course, I don’t have an AH-705 in hand to test yet, so there’s no way I can comment on performance.

Still, I can’t turn of the reviewer inside so I feel I can make some superficial comments assuming the specs don’t change.

Potential positives?

  • Complete integration with the IC-705
  • Could (potentially–?) be permanently mounted outdoors at the antenna feed point as a dedicated remote tuner
  • IP54 dust and water resistant
  • Power from internal batteries and an external DC source
  • It’s an Icom product, so I would expect excellent overall quality

Potential negatives?

  • Maximum wattage is only 10W, which I suppose is okay if you never put an amplifier between the IC-705 and the AH-705
  • Based on Icom specs, the AH-705 is larger than other portable ATUs at 7.5 × 4.1 × 1.6 inches. For example:
  • Some have noted pricing around $350 US price–that’s a premium for a portable ATU considering the Elecraft T1 is $180 assembled and many LDG models are less than $200. Of course, none of those ATUs have an IP54 rating, either.
  • Speculation here, but the AH-705 might only work with the IC-705 or Icom radios with similar ATU commands. One original pre-production prototype image of the AH-705 shows a power switch; the latest images do not. Like the mAT-705Plus, I’m not sure if the AH-705 can be turned on in order to tune only via RF sensing without essentially modifying a control cable to trick the ATU into powering up.

I was a little surprised to see that the AH-705 “only” has 45 tuner memories. In truth, I never really pay attention to this spec because I’m primarily a field operator. My radio sessions are only an hour or two long and I routinely pair my transceivers with a wide variety of antennas, so a portable ATU never has a chance to develop a complex tuner memory map for any given antenna. But as a reviewer, I try to step in other operators’ shoes so I see where this could be a slight negative for those who plan to use the AH-705 at home and connected to only one antenna. As a point of comparison, the mAT-705Plus has 16,000 tuner memories. Still, memories only help shave off a bit of the auto-tuning time. This would never have an impact on my purchase decision.

Biggest positive for me? IP54 rating

Since the AH-705 is designed to be dust and weather resistant,  it could be mounted at the antenna feed point. At home, perhaps it could act like an externally-mounted, remotely-controlled antenna tuner. I’m not sure what the maximum length of the control cable could be, but Icom Japan even lists a 16 foot control cable as an accessory. Of course, you would still need to follow Icom’s guidance about protecting the antenna, transmitter and control cable connection points.

Biggest negative for me? The size.

If the AH-705 specs are correct, it’s a little surprising Icom designed a portable ATU that’s this large. As you can see in the image above, it easily fits in the LC-192, but frankly since I’ve been an Elecraft T1 tuner user, I’ll notice that the AH-705 is 3.1″ longer, 1.6″ wider, and .7″ taller than the T1. It will certainly take up more backpack space.

Of course, unless I build an IC-705 control interface for the Elecraft T1, I can’t directly pair it with the IC-705 like I could with the AH-705. That said? I personally prefer pressing a tune button on the T1 and sending “QRL?” instead of hitting the PTT or CW key and allowing the IC-705 to kick in a continuous tune cycle for a few seconds. You might have noticed in some of my videos that when I tune to a new CW frequency, I’ll listen for activity, then tap the TUNE button on the T1 and send “QRL?” or “QRL de K4SWL”. By the time I’ve sent that string, the T1 has typically already found a match.

How will it perform?

I’ve got to assume the AH-705 will perform well. Icom tends to give their products thorough QC before shipping them to customers. I don’t anticipate any issues with the AH-705 as I did with the original maT-705, for example.

I’ll plan to test the AH-705 after it’s available.

For more information about the AH-705, check out the product page on Icom Japan’s website.

10 thoughts on “Icom publishes AH-705 antenna tuner details”

  1. I think icom may have just lost my interest. First downside is size and the second is price. I already have a Elecraft T1 integrated to to the 705 to work just like the MAT-705 and for high power use I have a Z100 Plus705 that I just purchased and will be testing out soon. For portable ops I don’t see me using the Z100 Plus 705 so the size of that tuner really doesn’t matter. Having weatherproof rating is not really a bonus for me. I’ve operated from a park shelter many times in a downpour and my non weatherproof tuner is safe under the shelter with me as is the radio. The low number of tuning memories is more of a disappointment than a drawback. A full tune by any tuner is not really that big of a deal, what’s an extra second or three.

  2. Like you, tuning time almost never factors into the equation for me.

    Don’t get me wrong: it was pretty cool last week when I was activating a park with the IC-705/mAT-705Plus and went back to my 40 meter frequency, pressed the key and it only took a fraction of a second to tune.

    Still, if it takes three or five seconds, so what? I think it’s a low-priority feature for field ops.

    Looking forward to your LDG review!

    73,
    Thomas

  3. 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 this 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′.

    One other request… I’m curious whether you’ve ever experimented with the AL-705 mag loop, and the AL-705 enhancement kit sold by Alpha? I plan to do some POTA activations from relatively busy suburban parks, and I feel like a mag loop with a tripod might be more practical for a picnic table activation than trying to get a wire into a tree.

    https://alphaantenna.com/product/al-705-enhancement-kit-for-the-icom-magnetic-loop/

    Bruce
    W0MBT

  4. Hi, Bruce,

    So my reply–just addressing the ATU part–got so long, I turned it into a post. Just published that here.

    I have not experimented with the AH-705 mag loop. I actually have a W4OP loop and a Chameleon loop for field use, though.

    I love loop antennas for their portability, low-profile, and their ability to be self-supported. Here’s my review of the W4OP loop (I haven’t reviewed the Chameleon loop yet).

    At the end of the day, I don’t use loop antennas unless I need a super compact antenna and there really are no easy options for wire antennas or even verticals. The main reason is because loops have a very narrow bandwidth and can be a pain to tune since standing near the antenna while tuning actually affects it. In other words? They can be finnicky.

    Activating a park or summit is actually an ideal application for a loop antenna since you’ll likely find a clear frequency, tune up, then stay on that frequency as you call CQ and work stations. If you want to chase other parks and summits, though, you’ll probably have to tune the antenna each time you move more than a few kHz. It gets old.

    I would also consider the Wolf River Coils TIA vertical–it’s a very popular antenna for POTA ops who don’t want to use wire antennas. Also check out the Chameleon CHA MPAS Lite.

    Or, you could build an antenna like the QRPguys Tri-bander and use a self-supporting fiberglass pole to mount it.

    Actually, there are a TON of antenna options you could build and pair with a fiberglass telescoping pole for support. You’d get the benefits of a wider bandwidth antenna, yet not have to support it with a tree.

    That said? 75% of my activations are still with a wire antenna hanging a tree. 🙂 I find it the most simple and effective field antenna–but most of the parks I visit have trees.

    Clear as mud? 🙂 I hope this helps.

    Cheers,
    Thomas
    K4SWL

  5. I don’t think the “limited” number of tuner memories is a serious issue, consider its intended use cases:

    Portable: Every operating session will be using (essentially) a brand-new, never before seen antenna system – when the antenna system changes, the memories are useless.

    Fixed base: while the antenna system may likely be permanent/static, operators *tend* to operate the same basic frequencies – nets, watering holes, etc. along with mode-specific frequencies (FT8, FT4, WSPR, and so on).

    The real question is how far off-frequency can you go before the AH-705 will force a tune? Every operating frequency change doesn’t require the tuner to tune.

    Clearly the AH-705 was designed first and foremost to be a portable, QRP AH-4, and as such it looks great. I like the idea of a portable tuner that installs at the antenna feed point, rather than at the radio end of the coax. The size I can live with, and the internal batteries make portable operation simple. (Is the size really so bad compared to other internal-battery tuners, like the LDG Z line of tuners?) and the price – unless an Icom representative gave you a number, it’s pure speculation. Personally, I would SPECULATE that the price will be in line with the AH-4 tuner, not $350.

    Honestly, a large number of users will windup filling the AH-705 memories with the various FT8 and FT-4 frequencies and a handful of SSB/CW calling frequencies during an operating session.

    Seriously, how many frequencies do you operate on a portable activation? Is it closer to 45 or 16,000? And the issue really isn’t how many unique frequencies you use in an operating session with a given antenna system, it’s how many frequencies you will reuse – that is where tuner memories are most useful.

    I like what I see so far for the AH-705, especially after my failed attempts to operate with a magloop antenna – a portable AH-4 act-alike with internal power tuning a long wire antenna could be just the ticket.

  6. Hi, Ken,

    Yeah, regarding tuner memories as I state in the post:

    “I was a little surprised to see that the AH-705 “only” has 45 tuner memories. In truth, I never really pay attention to this spec because I’m primarily a field operator. My radio sessions are only an hour or two long and I routinely pair my transceivers with a wide variety of antennas, so a portable ATU never has a chance to develop a complex tuner memory map for any given antenna. But as a reviewer, I try to step in other operators’ shoes so I see where this could be a slight negative for those who plan to use the AH-705 at home and connected to only one antenna. As a point of comparison, the mAT-705Plus has 16,000 tuner memories. Still, memories only help shave off a bit of the auto-tuning time. This would never have an impact on my purchase decision.”

    For a portable op? Memories are a non-issue. 🙂

    You also asked: The real question is how far off-frequency can you go before the AH-705 will force a tune?

    This will honestly depend on the bandwidth of the antenna. If it’s super narrow, like some verticals or a loop, tuning could be frequent. If it’s like most of my antennas, I bet the re-tune threshold is healthy enough it would cover the bulk of one mode of a band.

    I think it’s probably a very wise decision of Icom to carve out a bit of market by making the AH-705 somewhat unique in the world of portable ATUs. I’m sure they’ll sell a lot and, yes, I should hope the price will settle below $300 US.

    73,
    Thomas

  7. What is the protocol for an external atu with the 705.

    Am i correct that an atu connected to the 705 enables the Tune button.

    Pressing Tune causes the Atu to tune and it responds with a logic low back to the 705.

    Or?

  8. I’m not certain what the protocol is. The ATU does engage if you press and hold the tune button, or if you press the PTT or touch the key/paddle after moving off frequency enough to effect the SWR. Perhaps someone else can chime in regarding the protocols.

  9. I’ve searched high and low for the size of the DC plug (13.8V) for the AH-705 without success. Does anyone know the size/dimensions for this plug or a source for a pre-built plug/cable? I requested this info from Icom tech support and they replied with EIAJ-01…totally incorrect!

  10. After repeated attempts to get Icom America to reply to my request for the size/dimensions of the DC 13.8V plug on the AH-705 (first reply incorrect as stated above) and no further reply, I simply measured the included plug. It is NOT the same dimensions as the DC in on the IC-705. The dimensions are 3.5mm O.D. X 1.35mm I.D. X 9.0mm plug length. This size does not follow any EIAJ standard.

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