Following testing of our new QTH transformer using a Fair-Rite 2643101902 Mix 43 round core, I thought it would be a good idea to do the same for our 300W model, which uses the Fair-Rite 2643251002 Mix 43 core. This core is the one I use for the 40m, 20m, 15m, and 10m band antenna at my QTH as an inverted L.
I rate this core in our shop we sell the completed antennas as 300W SSB, but I frequently use it at 400W SSB and 150W Data, making this core a good choice for medium power applications.
Anyway, let's continue with the testing. The transformers were wound 56:1. The PCBs were soldered together by flipping one over and soldering the antenna and counterpoise tracks together, then connecting the SO239 point using a short length of RG316 to the VNA.
You can see the two boards together, including some uncleaned solder flux.
Anyway, here are the results, with some very small adjustments for the cable loss.
This really is good: over 90% efficiency from 80m to 10m.
It might be possible to get this a little more efficient with different windings or as an autotransformer. But for now, this is a pretty good result.
And here is the original VNA sweep with the cable loss.
Here is the test result from which the efficiency data is taken.
Anyway, great results again.
Just for comparison these are the two cores next to each other. Fair-Rite 2643251002 Mix 43 core on the left Fair-Right 2643101902 on the right.
Chris, M0VUE
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