Operating from the USS Cobia, a WWII Gato class submarine has been a bucket list item for me. The Cobia is docked at the Wisconsin Maritime Museum in Manitowoc, WI and I’ve long known that there is an active group of hams that put the sub on the air for the annual Museum Ships weekend. This year my schedule aligned with the event and I got that rare chance to be a part of it.
You can watch this week’s video I put this SUBMARINE on the air! Ham radio on the USS Cobia https://youtu.be/zoBYcBkpYGo
My first contact with the Cobia was, I believe, in 2001. We were down in the Milwaukee area visiting my in-laws and I took at trip to AES (now Ham Radio Outlet) to purchase my first HF rig, an Icom IC-718. I wanted to get on the air right away so I also picked up a mag mount and 40 meter Hamstick antenna to get on the air at their house. Cruising the dial, I found it was Museum Ships weekend and I picked up two boats that day: USS Cobia and U-505 the German U boat at the Museum of Science and Industry in Chicago. Since then, it has been a long dream to be a part of it.
Fast forward almost 25 years and I get the invite from the organizers. Come Join Us! How could I pass that up. Suffice to say, I had a blast and I can’t wait to do it again. Maybe again this Veterans day weekend when they put the sub on the air again.
Cobia is going into dry dock this fall for maintenance and repair. While the sub is in remarkably good condition, the maintenance will assure that Cobia will be around for future generations to learn its story. You can help out with the effort: https://www.wisconsinmaritime.org/collections/submarines/uss-cobia/cobia-dry-dock-project/
Field Day Plans
I like to use Field Day for trying new things. The contester in me says to stick with the tried and true to rack up the contacts. But the experimenter wants to do something different. Sometimes things work out, and sometimes not so much. This year I’ve had delta loops on my mind. Playing around with Chameleon’s TDL and REZ’s Scout antenna system has got me thinking of building a larger resonant delta loop for Field Day. My goal is to deploy a vertical delta loop resonant on 40 meters.
The problem is that I’m not sure if I’ll have the space. We are setting up at Black Lake in the Chequamegon-Nicolet National Forest, and while there are a lot of trees to hang antennas from, there are a lot of trees. A 40 meter loop is roughly 47 feet on a side. That’s a lot of space and I may have to scale down to a smaller 20 meter loop and try something different for the 40 meter band.
But why a delta loop? Aren’t they inefficient? The inefficiencies of delta loops mostly stem from their feed point transformer and from using them on bands lower than their fundamental. A corner fed delta loop will be vertically polarized with a takeoff angle about 25 degrees and on its fundamental frequency have the gain slightly better than a dipole.
The vertical polarization is important to me as we try to minimize interference between the other stations at the site. So a mix of vertical and horizontal antennas with careful placement is crucial
So here’s my quandary. In reading about delta loops, the formula seems deceptively simple: loop circumference in feet = 1005 / Freq MHZ. Make a slight adjustment for wire velocity factor and divide by three for each leg. Is that all there is to it?
I want to believe it is that easy. I’m currently reviewing my ARRL antenna book and copy of Rothammel’s along with scouring the ARRL QST archives (and a few websites) for whatever information I can find. Except for a few slight variations, everything is point to the same basic formula.
Maybe I’m overthinking it. I’ve got time until Field Day, so I’m going to put together a smaller 20 meter loop to test my ideas. If that works, then I scale up to the bigger boy for the event itself. Let me know what you think. Drop a message if you have experience with delta loops.
Finishing up
We’re heading out again this weekend down towards the Wisconsin Dells. Look for me to activate Rocky Arbor State Park at some point (that’s were we are camping), and I plan on a special park activation on Saturday afternoon. That one will be rather fast, so watch closely and act quickly.
Coming up next week I have a special interview with one of the organizers with the 13 Colonies special event. 13 Colonies is a fun event that run from July 1-7 and stretches across several states. You don’t want to miss that one.
I hope to get you in the log soon
Michael
KB9VBR
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