Suitcase DXPedition Station Automation (Part 3); 2×6 antenna switch

It’s a bit like being a mid century pioneer traipsing along the Oregon Trail. You somewhat know your destination, you take comfort from the fact others have completed the journey but yours will be unique and success is inherent in your own abilities. Tenacity and luck do count.

Unlike yesteryear pioneers mine doesn’t risk life nor limb and is conducted from the safety of my study/den and my garage/workshop. I’m inspired by Ken’s super station VY2TT in PEI and like the pioneers know roughly where I’m trying to get to but the details are very opaque.

Pioneering across the internet I’m confronted by a few specialized sites that have an array of large and equally large price tag for boxes that seem to do what I want. The penny hasn’t quite dropped and much of what I look at is conceptually clear but the detail is very murky.

Size has already disqualified most and so I’ve taken the seemingly easy decision to build my own suitcase DXPedition station automation gear. Optimism is a double edged sword and with an easy decision has come a much harder implementation.

I’ve built many electronic circuits from the simple using primitive techniques to sophisticated kits. Kits really can be the gold standard as you typically get an enclosure (box/cabinet), all the parts (resistors, transistors etc) and most importantly a circuit board (PCB) that you solder all the parts to and then mount within the enclosure. Within this gold standard, Elecraft stands amongst the best as do smaller more boutique kits from Pacific Antenna.

With two of my suitcase DXPedition parts built (an SO2R controller and band decoder), I’ve turned my attention to building what I hoped would be the final initial thing. Its a  gizmo that will allow me to  operate two radios simultaneously (either operated by me or two separate operators) while sharing a family of antennas.

Antennas vary in size and capability and in of itself is a huge topic but suffice it to say that any “serious” suitcase DXPedition will have a medley of different antennas. Sharing them quickly, effectively and safely is a non trivial task that warrants a dedicated gizmo/box and this one is called a two by six (2×6) antenna switch, as in two radios sharing up to six antennas.

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Here are serious collection of antennas at Ken’s VY2TT station in PEI
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A more modest collection used by us in Costa Rica

In my virtual wanderings I’ve stumbled across two internet sources for a 2×6 antenna switch PCB. One is domestic and the other from deep within the woods of Sweden.

  • KK1L’s 2×6 PCB available here 
  • SM2WMV 2×6 and Interlock PCB available here

As is my want I ordered both and settled on building the Swedish woods product first as it comes with a little more protection (the interlock PCB) to avoid a disaster when both radios have ownership of the same antenna and eventually as some point one radio is essentially history, blown up and kaput.

There’s something interesting happening in the Swedish woods in that Mikael (and I presume friends are building the SJ2W contest station. He is sharing regular updated and snaps of dirt, concrete, metal, back-hoes and even boots covered in snow but its clear this almost has a “data-center” feel to it with cleaning and neat wire runs, racks to hold stuff and so its no surprise that the pair of PCBs look very clean and professionally designed/manufactured.

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SJ2W contest station deep in the Swedish Woods….design center for the two PCBs?
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From the Swedish woods. Boards by Mikael Larsmark (SM2WMV)

I like lots of things about the Swedish woods 2×6 including Mikael’s BOM. Not the kaboom type but a list of parts and most importantly where to get them.

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A BOM snippet…..really useful list that makes my build much easier

Stuffing the two boards is a relatively easy process and I used pictures of the completed project on Mikael’s web site as a guide.

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Relays on the main board
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Antenna coax connectors on the main board

Surface Mount Technology….can be intimidating

The classic kit building world has been made all the easier through the availability of “large” components. Resistors, capacitors etc while small can be easily handled and are designed to be soldered via their long wiry leads to a PCB. Machines don’t suffer from human failings of clumsy thumbs or bad lighting and sadly these classic components are being replaced by eensy teensy legless equivalents called Surface Mount Technology or SMT. The mere mention will send builders in apoplectic fits. Fortunately small comes in various sizes and “big” small is still manageable for the most determined and with that mind set I set to and soldered these eensy teensy little legless wonders to the board. One escaped the table and I was resigned to ordering a replacement and biting the bullet on shipping when a chance search recovered the errant object using a Colditz style search light to track down the escapee.

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“Big” SMT components can be solder if you are determined and think you know how!
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Did I say small…..that is a diode
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Capacitors…bend the packaging and it makes a great catapult

Design for manufacturing 

Checking component orientation and board spacing was key as Mikael has a Hammond enclosure in mind for the project and I didn’t want to complete the PCB builds only to discover up a few millimeters off in key directions.

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Verify as much mechanicals early on ….
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Fit with the coax connectors I purchased?

Almost complete ….

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Completed main board
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Completed interlock board
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Two boards matted and ready for two final tasks; the enclosure and an inductor

 

Was it worth it?

Hell yes.

Could I have bought one ready made? Sure but I’ve learnt so much from this process and I feel like a pioneer that has arrived safely.

Was it cheaper than buying? Possibly but I do have enough parts for two antenna switches and still think I came out ahead. It’s very heart warming to see what fellow hams in what is a boutique corner of a very niche part of the larger hobby are doing and offering to others. Thanks to Mikael (SM2WMV) and Ron (KK1L) for leading the way and helping a virtual colleague get one step closer to his goal.

One of the joys of life is the opportunity to continue learning, achieve a tangible goal and have something useful to boot. Competitive contest stations are inherently complex, bulky and expensive. My portable version dubbed a suitcase DXPEdition station inherently needs to be effective, redundant and weight/volume minimized. While an “away team” could be 4+ operators all bringing different stuff toward the larger goal, I wanted mine to meet my goals and support me if I am the only operator and not have to rent a Lockheed C5 Super Galaxy plane.

So far I’m happy with the size/weight dimensions of what I have built including Mikael’s 2×6 switch.

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My solution can’t dictate renting a C5 Super Galaxy

What’s next?

In theory nothing but a little surprise nabbed me dictating a lot of rethinking and finding a different approach but that is the subject of another post.

 

 

 

 

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