BITX40 Rebuild Progress Report, MiscDotNews

BITX40 Rebuild Part 3: Back On The Air!

ATU-10 QRP Auto-Tuner emerges. And, a uSDX killer?

If go to Ebay or any of the numerous importing websites, you’ll find kits under the name “ATU-100 by N7DDC” such as the screenshot shown to the right or here on Amazon. That’s great, but it’s a bit overkill for us QRP guys, especially if we’re running portable! We need something battery powered, low current draw, and small. And with BNC connectors. Well, David, N7DDC thought so too! He’s released the ATU-10. It features latching relays, is powered by Li-Ion batteries, and fits in the palm of your hand:

Images used with permission from N7DDC

ATU-10 Details

With the ATU-10’s latching relays, the tuner does its job by setting the correct relay positions and then turns off. It stops using batteries. It’s conceivable that the batteries could last a very long time on a single charge. Additionally, it can be charged over USB-C, and so any power bank can keep it going. The same connector also facilitates firmware updates. You can learn more about the tuner at the official announcement:

The official Github repository is here:

One doesn’t need to think too hard to consider a nice little QRP CW rig that it will pair nicely with.

A uSDX Killer?

David’s also let an interesting detail loose from the thread linked above:

Next design – the QRP 5W SDR transceiver in the same case as this tuner and it will be technically perfect device, unlike uSDX.


Whoa, shots fired! Some have accused my own review of the uSDX as being less than charitable, and it’s the subject of hot debate in various circles. But it’s got people thinking, and if we can see a micro SDR such as this, it’ll be a great innovation that I for one will be eager to see.

As for now, we’re not aware of the ATU-10 being sold in kit form yet. As with many other industries, ham radio is having a parts shortage too. David does intend to sell kits. And since the design is Open Source, you can be sure The Usual Suspects will be selling imported versions of it soon.

“HAM” or “ham”?

On another note, does anyone have any information as to why so many people capitalize “ham” when referring to “HAM radio”? It’s not an acronym and dates back to the term “ham fisted” as far as I can tell. I’d love to hear your input in the comments below.


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    • econjack on July 1, 2021 at 6:33 AM
    • Reply

    There is a kit for this on Amazon (#B08TWTZH2T) for $40. Al (AC8GY) has one and is very happy with it. BTW, we are building our own SDT which will be a 20W SSB/CW, 80-10M rig. The rig will be Open Source and, with 5″ display, should cost under $200. It is designed to be “hacked”: I can send a screen shot of rcvr display if you want it.
    Jack, W8TEE

    1. Hey Jack, thanks for the comment. Yep the ATU-100 has been around for some time, seen here as you mentioned: The ATU-10 isn’t out yet. I’d love to hear about your SDT, shoot me an email geocrasher at gmail. Thanks and 73 🙂

  1. Has anyone built that ATU-100 kit on Amazon? For $40, that seems like an awesome deal.

  2. ham vs HAM is easy and I 100% agree with you. If you really want to get folks worked up how about 73 vs 73’s’s’s’s for your next one…

    • John on July 1, 2021 at 7:56 AM
    • Reply

    See lots of boards on ebay for this, but not a tremendous price difference for the 817 LDG.

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