Station Switchbox project

The Station Switchbox project page you are viewing is more of a story than a how-to, and I hope you can glean ideas from it for your own design and build process. I consider myself a newbie in this area as I know what the end looks like and I can generally work backwards from the end, but I lack skills with electronic and mechanical design tools except a Staedtler mechanical pencil and eraser thanks to drafting in high school. Anyways, I talked about this project on Ham Radio Workbench episode 130.

In the spring of 2021, after seeing this awesome presentation from Bob Heil, he spoke about the features of the Pro7 headset. As an aside, watch the whole video as it explains a lot about the basics of audio. So working at The Candy Store(tm) as I do, helping other hams to purchase their gear and solve their issues, I decided to leverage my staff discount and take a pair home.

But that created an issue – if I wanted to use it, cables and adapters would be all over the front of the small corner of my desk where my gear lives. And as a guy who hates clutter and has limited operating space, this simply wouldn’t do. I needed a solution .. enter the VE6LK Station Switchbox. But first, a photo of the finished product in it’s final place.

The final product in production

I entered into the design phase and mapped out my needs:

  • I do HF net control from time to time, and I live in a noisy location, so I need to use offsite SDRs to hear stuff my station can’t.
  • I wanted a quick and easy way to change between my boom mic and footswitch to the headset and possibly hand switch.
  • I wanted to be able to route computer audio either into speakers as normal or into one side of the phones so SDR is on one ear and radio on the other, and balance between them.
  • A passthrough for CW key input.
  • Handles my T/R relay for local SDR isolation and a pretty “on-air” light.
  • Oh, and thanks to common mode issues, it needed to be RF shielded and properly isolated.
Early design notes

I went through a few paper sketches to map out what wire goes where and how big the parts were and how they’d fit in the enclosure I had on hand, and I drove myself batty with an eraser, too. Then I discovered as a browser-based Visio-like tool and got to work. I was so happy about that I showed it off to the Cycle25 Hub not Club. solved several problems for me:

  • quick and easy editing like Visio
  • it’s free to use allowing me more money for radios
  • it was fast to build visual objects and replicate them, like when I needed to do physical panel layouts as seen below
Panel layout made easy

But it wasn’t all sunshine and roses, one switch I placed ran into a box support:

Whoops (the switch got moved)

Overall made life easy, and the rest was up to me to assemble it and test it. Here are some progress photos.

Then I moved along to testing the device. It was here I ran into issues with shielding and grounding allowing stray RF to go places it shouldn’t, like into my Mic audio. Yes, I should have corrected the common mode “rf in the shack” issues first, but I should probably do a lot of things as there always seems to be something new to pursue – squirrel!

Final schematic

I took a systematic approach to testing. I tried one thing at a time, then tried them in an additive fashion. In this way I could figure out what was causing the latest gremlin to appear in my finely woven plan.

EMI shielding paint applied

I didn’t anticipate RF shielding -or lack thereof- on the inside of the enclosure as an issue. But this hitch was was easily proven using some aluminium foil from the kitchen as a shield in the short-term and some MG Chemicals Super Shield Conductive Paint spray before I did final assembly. I’ve used the spray on two other projects since then .. it isn’t cheap but you don’t need much either.

Is it pin 1 to 8?
Or is it pin 8 to 1?

The world of connector numbering is not a lot of fun. Some will make notes “facing connector” others “facing solder pins”. Given I was interfacing to a Yaesu, neither was noted so I had to do the ole’ trial and error approach .. sheesh.

Not as neat as I wanted

One last note, that when you undertake spaghetti wiring projects like this, no matter how hard you try it can still resemble a jumbled lot of wires. While I wanted it super-neat and super-clean, I’ll take this as acceptable. Most functions have unique wiring colours and types which makes any future troubleshooting simple. Yes, I have paper drawings annotated with wiring colour on hand in my cabinet for reference.