June 2024 ADX Buildathon

It all started with very good lecture by Richard Hinsley VK2ARH/W5ARH on the ADX (the Arduino Digital Transceiver) in April 2024 followed by an email to all from Michael VK2MDP asking around about interest for a club buildathon, very quickly the list of interested members grew to 28 people wishing to grab a kit, many to attend the 2 buildathon sessions, others either not local, not available or just wanted the challenge to try it on their own.

The ADX Buildathon workshop dates were:

• Wed 26-Jun-2024 – 7:30pm to 9:30pm Winding toroids for the low pass filters.
• Sat 29-Jun-2024 – 9:00am to 5pm ADX Build and Testing … and mandatory BBQ.

Winding Toroids evening (26-Jun-2024)

Not even a State of Origin critical game could stop a 17 member squad to register to tackle toroids, you can always watch the game later, but winding toroids home on your own could end up been a grind. Tonight was an earlier kick-off at 7:30, some members had to scramble their pizza to be there on time. There was no grounding this evening, all this will happen on Saturday. The only penalties awarded will only be discovered when testing the final product on Saturday.

Richard VK2ARH provided some guidances and instructions on how to wind the toroids and all started … interesting to see how many magnifier glasses are needed.

ADX Build and testing (29-Jun-2024)

It’s all go, people lining up at 8:30am, Tim complaining that someone has already started the fire! People have heard about it, it attracted new possible members to the site. Many other members came to visit to see what the whole thing was about!

Pictures takes by themselves.

Time to break … Thank you Dom VK2JNA for cooking a feast.

David VK2DRT’s ready ADX under test on youtube

Testing at home post build-a-thon by David VK2DRT

After much stuffing around I finally got my first QSO with the new ADX. See screenshot below. I read carefully through all the calibration suggestions, but not having a radio with spectrum display I thought – why not use the club’s WebSDR? I did the following on 15M but it would work on any band.

Set the WebSDR to 21,074,000Hz, USB. Zoom in as below. Find a relatively clear section of the band. Here I chose to target 21074.800 Set the ADX to 15M mode (21.074MHz), and set a Tx frequency of 800Hz. Click the “Tune” button. The ADX will transmit a solid 800Hz tone which you can hopefully see as a solid vertical line at 21,074,800Hz. You can do the same anywhere you find a clear spot. Note where your ADX is actually transmitting. Mine was off by quite a bit. Recalibrate by holding either CAL button for say, two seconds, save and try again. Eventually you’ll get down to just a few clicks up and down and you’ll be spot on.

Once done, I was able to get a QSO. In my limited understanding of FT8, I think the fact that VK3DEK reported (almost) the same frequency (2424-2425Hz) also means it was spot on.

Pro Tip everyone from Richard VK2SKY: on the club’s KiwiSDR, when tuned to an FT8 frequency, if you click on the FT8 label above the waterfall (not the chain link link icon), the Kiwi’s FT8 decoder will open up and you’ll see all the traffic on the frequency:

…and if you then click on any underlined station in the decoder display, you’ll jump to that station’s QRZ page. Click on the pskreporter.info link at the bottom left, and you’ll a maps of stations heard during the last 24 hours.

Comment from Jeff VK2ESE (30-jun) following the post and email traffic on the reflector:

• That does it! All the great photos and comments regarding the ADX project has belatedly wet my appetite! There has been some indication that spare ADX kits may possibly still be available.  If so, who can I ‘bribe’ to procure one? Would love to get one of VK2YU’s printed cases as well! Probably well past time that I ventured into the 21st Century! Cheers, Jeff  VK2ESE

Then on 1-July from Dom:

• Richard, If there is spare kits, Rod VK2ZZM & myself Dom VK2JNA would be happy to purchase. We didn’t first time around because we are both outside of Sydney most of the time but will run a couple of build nights at Rods farm near Gundaroo, Let me know. If only one spare, Rod would appreciate it. I can look over his shoulder.

Enclosing the work

A 3D printed enclose was developed by Simon VK2YU.

Members building the ADX:

• VK1LL Kit
• VK2AHA Tommy
• VK2AXC Brian
• VK2BFB Lindsay
• VK2CAR Carmel
• VK2CLF Clifford
• VK2CRJ Gary
• VK2DRT David
• VK2EMM Emmanuel
• VK2JCC Colin
• VK2JQA Warren
• VK2MDP Michael
• VK2MYK  Nic
• VK2SKY Richard
• VK2TGO Geoff
• VK2TIJ Tim
• VK2TMF  Mal
• VK2VKP  Rajesh
• VK2XE Greg
• VK2XPL Philip
• VK2YMI Brendan
• VK2YU Simon
• VK2ZWD John
• VK2ZYP Zara
• VK4MQ Bruce
• St Clair Malcolm

Many thanks to many members for organising this event, and specially Richard Hinsley VK2ARH/W5ARH for the procurement, preparation of all the kits and mentoring, Sean VK2THT for the logistics and Mal VK2TMF for catering.

More photos, courtesy of Raj VK2VKP:

Back again at the regular weekly meeting on 3 July, the stragglers complete the construction work and testing:

1-Jun-2025 update

Following several requests regarding the possibility of operating the ADX on 160m I decided to modify the firmware to provide 160 as an option and with the help of fellow Amateur Radio Operators in my local radio club, came up with a low pass filter specification for a 160m. Whilst there is still some room for optimisation, a workable 160m ADX is presented here. Thanks to Geoff Osborne VK2TGO, Clifford Heath VK2CLF and Jeff Skebe VK2ESE for their efforts and input to the LPF design. The firmware along with lots of ADX documentation is available at my GitHub site: https://github.com/VK2ARH/Cowtown-ADX-Project. Any future improvements to the 160m LPF will be published on the GitHub site.