I had a topic on the mind as I made my way back to the trailhead after a SOTA activation recently.
I get a lot of questions from readers and subscribers about resonant vs. non-resonant antennas and whether or not an ATU is a good or bad thing.
If you know me, you’ll know that I tend to lean towards qualitative research; meaning, I like to base my opinions on first-hand observations rather than laboratory or textbook explanations. Part of the reason is I’m not an engineer, so specifications and performance stats don’t influence me–I don’t understand them half the time–rather, I base my opinions on trying or field testing.
The proof is in the pudding, right?
So with the topic of antennas and ATUs on the brain, I decided to turn on the action camera and do an unscripted video on the trail as I hiked back to my car.
This video is essentially stream of consciousness: I won’t blame you if you skip it.
With that said, if you manage to stay awake for the whole video (congratulations in advance) I’m curious what your thoughts are so please consider leaving a kind comment!
I’ve received no less than three inquiries this weekend from readers who are seeking advice about purchasing a portable external ATU to pair with their Icom IC-705 transceiver.
Fortunately, there are few options on the market and I believe there is no “right” one because choices are really based on operator preferences.
I’ll do my best to sum up my thoughts below based on the three ATUs I regularly employ and what we know so far about the AH-705 ATU from Icom.
Keep in mind this list will not include some excellent options from LDG, MFJ, and other companies simply because I haven’t used them in the field. Please feel free to add your comments if you have experience with other good options.
Mat-Tuner mAT-705 Plus
The Mat-Tuner mAT-705 Plus is the first external ATU on the market that directly pairs with the Icom IC-705 via a control cable.
The latest iteration–the mAT-705 Plus–is the ATU I can recommend.
Be careful if purchasing an mAT-705 used as you’ll want to make sure you’re getting the Plus version. The Plus version has a USB-C charging port on the front panel (seen in the photo above)–the original mAT-705 does not (it uses replaceable 9V cells).
Perfectly pairs with the IC-705 for full CAT control
Wide tuning range
Tuning is fast and relatively quiet
Numerous memories making repeat matching rapid
Internal rechargeable battery
Cannot be paired with other radios without modification (not recommended by the manufacturer)
At $220 US, it’s not the cheapest option
Because the IC-705 relies on CAT control for operation, if you leave the control cable at home or on a park bench, you will not be able to operate the ATU. (Pro)Fortunately, the CAT cable is a simple 3 conductor 1/8″ stereo patch cable.
Summary: If you’re looking for an ATU to take full advantage of IC-705 CAT control, the mAT-705 Plus is a great option. The only significant disadvantage of this ATU is the fact that it only pairs with the IC-705 (or possibly other Icom transceivers with similar CAT control). In other words, you can’t pair it with other QRP transceivers you might own.
The Elecraft T1 has been on the market for at least 16 years and is one of the most popular portable antenna tuners on the market.
Elecraft offers the T1 in kit form ($159.95) and factory assembled/tested ($189.95).
The Elecraft T1 has a CAT control port that has been used with the FT-817 in the past. Elecraft recently announced that they will also produce an IC-705 CAT cable that will allow full pairing with the IC-705 transceiver (much like the mAT-705 Plus above).
To be clear, though, the T1 doesn’t need a control cable to function: simply press the TUNEe button for one second, then key your transceiver.
Very wide tuning range
Soon it will have an IC-705 CAT connection cable option
Uses common 9V battery that is easy to replace in the field. (Con) Not internally-rechargeable like the mAT-705 Plus.
One of the most compact automatic ATUs on the market
Pairs with any 0.5-W to 20-W transceiver covering the 160-6 meter bands
FT-817 Remote-Control Option
Front panel buttons need protection while in your pack to prevent accidental pressing that will deplete the battery. I 3D-printed this simple cover that works brilliantly.
Summary: The Elecraft T1 is my personal favorite. Since the T1 pairs with any QRP transceiver, I love the flexibility. The T1 has also been on the market for ages and is a solid, safe choice–we know longevity is benchmark. I’ve never been in a situation where the T1 couldn’t find a reasonable match.
I will certainly test the new IC-705 control cable option when it is released in the near future–stay tuned.
The AH-705 is Icom’s custom ATU designed to perfectly pair with the Icom IC-705 via control cable. If you want an all-Icom setup, this is it.
Pricing in US dollars is TBD at time of posting, but the announced retail price is $350 .
Perfectly pairs with the IC-705
Wide tuning range
2-way power sources using alkaline batteries (2 x AA cells) or external 13.8 V DC
IP54 dust-protection and water resistance construction
Could (potentially–?) be permanently mounted outdoors at the antenna feed point as a dedicated remote tuner
In terms of overall size, the AH-705 appears to be the largest of the portable ATUs mentioned here
It doesn’t appear AA batteries can be recharged internally
The AH-705 may (we don’t know yet) only work with the IC-705 and possibly similar Icom models
The maximum power handling of the AH-705 is 10 watts–if you use other transceivers (if that is even possible) you would have to be extremely careful with power settings.
The AH-705 is pricey if the actual retail price ends up being near the projected $350 mark. Hopefully, it’ll be much less than this.
Like the mAT-705 Plus, the AH-705 will require a control cable for operation. (Pro) Of course this means it pairs perfectly with the IC-705 and can follow frequency changes without RF sensing.
Summary: Keep in mind, I have not tested the AH-705 yet, so this is only based on announced specifications.
The strongest selling point for the AH-705? 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.
The biggest negative to me is the size. Just check out how large it is compared to the IC-705 in this video. It’s still very portable, but the other ATU options above are much smaller.
Still: if the AH-705 is great at matching antennas and the price ends up falling below the $300 point, I’m sure it’ll be a very popular ATU.
Another option often overlooked are portable manual antenna tuners. I’m a big fan of the Emtech ZM-2 which is offered both in kit ($62.50) and factory assembled/tested form ($87.50).
It is a manual tuner, so requires manual input to find a match. While it’s not as easy as push-button tuning, it isn’t complicated either.
Here’s my routine:
I set the top right switch to “GROUND” if using coax feed line and “LINK” if using a balanced line.
Set the added capacitance switch “ADD” to “0”
Set the TUNE/OPERATE switch to OPERATE
I set both capacitors to middle positions (6 on the scale)
Tune to AM or SSB and listen to the noise floor as I tune the variable capacitors to maximize the noise level. I typically start with the left capacitor, maximize it, then maximize the right capacitor
If the antenna is particularly challenging, I might add 250 or 500PF via the ADD switch
Set the TUNE/OPERATE switch to TUNE
In CW mode, I key down and make fine tuning adjustments with the variable capacitors to make the red tuning LED turn off (high SWR makes the red LED illuminate)
Set the TUNE/OPERATE switch to OPERATE and hop on the air! (Often, I’ll double-check the SWR on my transceiver).
This sounds complicated, but once you’ve done it even two or three times, it becomes routine. I’ve yet to find a wire antenna the ZM-2 can’t match–it’s a very capable tuner.
The most affordable option listed here
Very wide matching range
Portable and very lightweight
Requires no batteries for operation
Although not complicated, there is a small learning curve involved
Each time you change bands, you will need to manually re-tune the ZM-2
Not as fast and hassle-free as an automatic ATU
Summary: I carry the ZM-2 with me even if I plan to use an automatic portable antenna tuner. If my auto ATU loses power for some reason, the ZM-2 will always rescue me. Plus, it’s just as capable of making tough matches as the ATUs above.
I also love using the ZM-2 to match antennas for shortwave broadcast listening outside the ham bands.
Even if you buy an automatic ATU, I would still encourage you to buy a ZM-2 as a backup. It’s affordable, reliable, and very handy.
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′.
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.
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.
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!