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Let’s Give it a Go: Pairing the Elecraft AX1 and Emtech ZM-2 Manual ATU

24 Comments

Last month, I received a comment and question from Gordon (KO4AYC) here on QRPer.com:

“I am curious if anyone has used the AX1 with the AXE1 40 meter extender and tuned this antenna for 40 meters using the Emtech ZM-2 tuner?”

For the life of me, I couldn’t remember if I’d tried this combo before.

The ZM-2 ATU is a simple manual antenna tuner that you can purchase either as a fun-to-build kit or fully assembled and tested.

I’ve owned my ZM-2 for many years, and I believe every QRP field operator should have one. They do a brilliant job of matching random wire antennas and taking your resonant antenna to a non-resonant band. Being a manual ATU, they require no power source. If you’d like to read a quick tutorial on tuning the ZM-2, read this previous post.

I figured the easiest way to answer Gordon’s question was to give it a go!

The AX1 does require a counterpoise, so before hitting the field, I did check to make sure there was continuity between the shield of the ZM-2’s BNC connector and the black binding post when the ZM-2 was switched to “GND” for coax antennas. Fortunately, there was! I loved this idea because it meant that no matter the radio, I knew I’d have an easy connection to ground for the AX1 counterpoise.

Blue Ridge Parkway (K-3378)

On Wednesday, February 21, 2024, I grabbed the ZM-2, AX1, and AXE 40M coil (since Gordon specifically asked about 40M) along with my Yaesu FT-818ND. It was time to see just how effectively the ZM-2 might match the AX1.

I store my AX1 in this Maxpedition pouch (see link in gear section below).

Upon arrival, I began setting up the station.

Even though it was approaching 2:00 PM locally, I wanted to see if the ZM-2 would match the AX1 (with AXE coil) on 40 meters first. I didn’t expect a lot of activity on that band so early in the afternoon, but I figured I could hopefully work a couple of stations.

I attached the AX1 directly to the ZM-2 antenna port and deployed the whip and 40M counterpoise.

It was a bit gusty, and I quickly realized that the AX1 might topple over in the wind. To secure the antenna, I used the handle of my GR1 backpack. It was a semi-effective arrangement (actually, the handle sort of pulled the antenna toward the pack, which wasn’t ideal either–I eventually removed it).

In calm conditions, I wouldn’t worry about the antenna toppling over; the ZM-2 provides enough of a base that it’s stable. In the wind, though, you’ll definitely need to secure the ZM-2/AX1 combo to keep it from being blown over.

My plan was to start on 40 meters, then also hit 30, 20, and 17 meters. This would give me an opportunity to see if the ZM-2 could match the AX1 on multiple bands.

Side note: I can’t remember if I mentioned this in a previous field report, but one sad bit of news for me is that there’s a new source of QRM at the Folk Art Center. It’s likely coming from the VA medical complex next door, but it raised the noise floor to at least S5 on most bands. This will make it more difficult for me to work weak signals from this particular POTA site.

Then again? My buddy Alan (W2AEW) recently pointed out to me that compromised antennas like the AX1 don’t feel the effects of local QRM as a higher-gain antenna would. I’d been thinking the same thing.

Gear:

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On The Air

I hopped on the air and started calling CQ POTA on the 40-meter band. I worked one station quickly (thanks, W5GDW) and then silence. I didn’t expect 40 meters to be active this time of day, but I didn’t think it would be completely dead either.

I checked the POTA spots page and discovered that the connection to the Reverse Beacon Network was down. Even though I scheduled the activation, the system hadn’t spotted me.

Once spotted, I worked three more stations in quick succession.

I didn’t hang around on 40 meters.

Next, I moved to the 30-meter band where I was able to find a match and add four more contacts to the logs.

I suspected that 20 meters would be my most productive band, but decided to hit 17 meters first, again, just to see how easily the ZM-2 might match the AX1. It wasn’t difficult at all to get a match.

I logged four more contacts on 17 meters, bringing my total logged up to 12.

Finally, I QSYed to the 20-meter band and easily found a nice match via the ZM-2.

No doubt, 20 meters was the most productive band that fine Wednesday afternoon.

I logged an additional 15 stations in 15 minutes before calling QRT! Woot!

QSO Map

Here’s what this five-watt activation looked like when plotted out on a QSO Map. Each line is colored to represent the band used in the contact (40M green, 30M orange, 20M blue, and 17M purple). Note that N7CCD wasn’t at his QTH in WA, but activating a park in PA:

Activation Video

Here’s my real-time, real-life video of the entire activation.  As with all of my videos, I don’t edit out any parts of the on-air activation time. In addition, I have monetization turned off on YouTube, although that doesn’t stop them from inserting ads before and after my videos.

Note that Patreon supporters can watch and even download this video 100% ad-free through Vimeo on my Patreon page:

Click here to view on YouTube.

ZM-2 + AX1–?

So, Gordon, I can safely say that, yes, the ZM-2 pairs nicely with the AX1 and AXE combo.

Since the ZM-2 maintains a connection to the ground post even when it’s switched to a coax input, this means that you can connect the AX1 counterpoise to the ZM-2 if your rig doesn’t have a convenient grounding point.

Since antennas like the AX1 have a high Q, and are affected by topography and body capacitance, you won’t be able to reliably position the L and C controls to the same positions each time. That’s okay, though, because the ZM-2 is fairly easy to tune.

You don’t need a perfect SWR–I’d be happy with anything under 2:1.

Do think about a way to secure the ZM-2 so that when the AX1 is attached it doesn’t topple over in the wind. The ZM-2 is super lightweight, so adding a (non-conductive/dielectric) weight on it, or using a bungee cord, will sort that out in short order!

Thank you

This little Albino squirrel did distract me at one point during the activation. I think I may as easy to distract as Hazel.

Thank you for joining me during this activation!
I hope you enjoyed the field report and my activation video as much as I enjoyed creating them!

Of course, I’d also like to send a special thanks to those of you who have been supporting the site and channel through Patreon, and the Coffee Fund. While not a requirement, as my content will always be free, I really appreciate the support.

As I mentioned before, the Patreon platform connected to Vimeo makes it possible for me to share videos that are not only 100% ad-free but also downloadable for offline viewing. The Vimeo account also serves as a third backup for my video files.
Thanks for spending part of your day with me!

Cheers & 72,

Thomas (K4SWL)

24 thoughts on “Let’s Give it a Go: Pairing the Elecraft AX1 and Emtech ZM-2 Manual ATU”

  1. Great post Tom.

    I love the packs/rucksacks that you use. I would really like to have a GR1 like you showed in this post but being a retiree I can’t afford the packs you use.

    So, I have a new pastime that I enjoy; finding a cheaper alternative on Amazon that matches as closely as possible the pack you use. I know the quality isn’t the same but I treat all of my equipment very nicely so the cheaper alternatives work pretty well for me. I guess you can call this just another aspect of the hobby that I really enjoy.

    Thanks again for all you do for the hobby.

    W4MKH

    P.S. I was up your way in Old Fort last Saturday but with the rain we just had lunch at Hillmans after the nursery grand opening and headed back down to Columbus. I didn’t even take a radio with me but rather just enjoyed the scenery. Planning on a Black Mountain trip in the near future so maybe I will get to do an activation next time.

    Reply

    1. Hi, Marshall,
      Nothing at all wrong with choosing less-expensive packs. It’s true that I fork out way more $$ for packs than most people. Pack and radios…I have a problem! 🙂

      Absolutely shoot me a message if up this way. Also, I’m WAY overdue attending a BRARC meeting. May see you there!
      Cheers,
      Thomas
      K4SWL

      Reply

  2. Hola, Along with the Elecraft T1, the original LDG qrp tuner kit, the ZM-2 remains a classic tuner for low power aficionados.

    Works in a power outage and on cloudy days
    Johnve3ips

    Reply

  3. Hi Thomas,
    thanks for another field report.

    I managed to buy a KX1 with all the trimmings recently, it was priced such that no matter the condition it was worth buying before anyone else could get it before me.

    Excited about my new toy I’ve been reading/watching a lot of your field reports with the KX1. One configuration I’ve missed on your site is the KX1 with a random wire binding post style antenna. I feel like this is a configuration that has a lot of potential pitfalls, so a report with the KX1 and this style of antenna would be much appreciated.

    Or if you know of a field report with this configuration and some tips, a link to that would be welcome.

    72 de LB1KJ / Erik

    Reply

    1. Brilliant, Erik!

      You’re going to love the KX1, Erik!

      You’re right that the binding post adapter with two wires is a powerful combo with the KX1. I’ve used this combo a lot. I would need to dig into my archives to find more examples, but this one immediately came to mind:
      https://qrper.com/2020/11/pota-field-report-one-elecraft-kx1-two-short-wires-and-three-watts-yield-1100-miles-per-watt/

      Hey, we’d love to get a field report from you once you get your KX1 on the air!

      Cheers,
      Thomas
      K4SWL

      Reply

  4. Great to see the nice results with the ZM-2 – I think I built mine back in 2007 or so. I made mine with the SO-239 connectors though. I (much later) retrospect, I wish I had gone the BNC route.

    Reply

    1. Oh my goodness, Alan! I remember watching that video years ago to refresh my memory. For some reason (likely because it wasn’t your workbench) I didn’t realize it was you. It’s an excellent tutorial.

      Reply

  6. Thanks for doing this AX1, AXE 40-meter extender and the Emtech ZM-2 tuner combination activation video Thomas. I will be putting an AX1 and AXE on my list for radio things to save for/get. 72 de Gordon (KO4AYC)

    Reply

  7. The ZM-2 does put some energy to the antenna port in “Tune” mode, but not much. In fact, I once completed an entire SOTA activation not realizing that I hadn’t thrown the switch to “Operate.” ????

    Reply

    1. Ha ha! I did the same thing at a POTA site I think back in 2020 or so. I recall the activation taking ages (I was using a random wire) and then realizing I still had the “tune” switch on. Doh! I did get my 10, but took a long time–back then, the hunter population was small.

      Reply

  8. What a timely piece! I received my ZM-2 on Saturday, and last Tuesday I was looking at my AX1! I see now I have another option.

    Great post, and thanks again for the suggestions for coax and other QRP sites. I placed orders with two vendors yesterday. ????????

    Reply

    1. Brilliant.
      I really do think every field QRP op should have a ZM-2.
      Have fun with it and the AX1!

      Reply

  9. Thomas,
    Great post & video… I love the idea of using the ZM-2 with the AX-1… and sighting the legendary white tree-hugger (squirrel), makes it a sign!

    I mounted (velcro’d) my QDX LoBander, TalentCell & ZM-2 to the back of a cheap android tablet. I’ve worked FT-8 using the FT8CN software. But it never occurred to me to attach the AX-1 antenna to it. Next time I deploy, I’ll pair it. After watching the video, I think it worked great!

    TU 72 de W7UDT

    Reply

  10. Fun combo, Thomas! I actually have been carrying the AX-1 and ZM-2 on all of my work travels, to pair exactly like that with my IC-705 as a backup stealth antenna, if I ever couldn’t use a wire antenna.

    When running that combo for a digital mode like JS8, I have found you need a choke on the coax to prevent problems with the radio/computer.

    Great to get you in a P2P during that trip! Weather was perfect. My next trips to that side of the country include Main and Florida. Maybe we’ll get lucky again 😉
    72! Michael – N7CCD

    Reply

    1. Now that would be brilliant, Mike. I’m 100% convinced that you have magic gear that can always hit WNC! 🙂
      Noted about the need of a choke. I see where that could be an issue with those high duty cycle modes.
      Thanks for the P2P, OM!

      Reply

    1. Indeed you do, William! I’ve been meaning to tell you that. What are you waiting on?
      Enablingly yours,
      Thomas

      Reply

  12. Hey Thomas,

    Thanks for the report and video. 🙂

    The ZM-2 can only be properly tuned when *not* distracted by albino squirrels. 😉 Also that QRM was pretty tough — strange that it was so strong there.

    72 and God bless you!

    Will Brokenbourgh
    AF7EC

    Reply

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