Of the various types of antennas I've built, I've never built a magnetic loop. It always seems like there's a bit of magic involved and relies on hard to get suitable air spaced variable capacitors.
By magic I mean people rarely give exact dimensions; and to find a suitable air spaced variable capacitor is not just a case of going to one of your regular electronic parts suppliers. However, I've seen VK3YE play with magnetic loops a bit lately and I know they're good for their small size, so I think it's time. Better yet, I believe they match a need I have.
This week-end I finally got around to starting to build my Softrock Lite II kit I purchased back in (I think) March – when I was still in F call (so RX only was the only sensible option from a license perspective). Seeing it's RX only (and due to thinking my shack computer may not have a stereo line in) I'm thinking it could be cool to just setup inside on my main machine. For that though, I need a nice simple antenna that I could have inside and thereby needs to be relatively small. (Oh, and I'm going for 40m.)
In my search for small magnetic loops I came across the G4ILO Wonder Loop. This is close to what I need, and could be fun to build and then use with my FT-817. Further, I also like the simple SWR bridge that is being used – may just build one up from scratch.
I like the way he explains figuring out the dimensions (and indeed the information that it's a simple 5:1 ratio between the loops), and I've also found an Australian supplier of variable capacitors. It's the local Jackson Brothers suppliers that have been advertising in AR Magazine for years but their website never worked so I left it there. But I finally took a punt and emailed them to see if they had a catalogue and price list. Turns out they do and were very prompt in it getting it to me.
So now I have a known supplier of high quality variable capacitors, an idea about dimensions for magnetic loops, and a need. All I need now is time! 🙂