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#1
I seem to recall reading somewhere that -43 was a good mix to use for the transformer cores however -52 supposedly performed slightly better but was more expensive. I made my first 49:1 transformer out of a pair of stacked FT140-43 cores and it worked a dream when I tested it on 80m wspr. I decided to get some -52 mix cores. I got a 150-52 and a bag full of 44-52 beads as they were cheap and I thought might be useful for threading over some coax to make a choke. Today I had the idea to make a 49:1 out of a couple of the 44-52 beads stacked. I used 4 beads and the finished transformer measures just 20mm long by 14mm wide. It might not stand up to much power but even if it dissipated a full 5w it's take a while to burn up. I'm going to go out and test it side by side with the 150-52 and 2x140-43 but if it works it'll make a brilliant transformer for prepping when paired with something like the LNR precision Mountain Topper. Actually come to think of it I have some small -43 mix cores too left over from another project so I'll make another out of four of those first and test all four over the next week or so. If they work I'll also try potting them in epoxy in a small container. I think I have an old APS film canister kicking around somewhere which would be ideal. I might be able to 3D print something even smaller though.