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Sometime back I mentioned to the list about experiments I've done using various numbers of jfets as well as trying different types. Using the 2SK715s (or the SMD equivalents), the input impedance steadily decreases with more paralleled jfets. Andrew Ikin decided four in parallel worked for a loop amp? low enough input impedance to give LF-HF response. If your interest is only HF then the higher impedance resulting from only using two in parallel each side might be OK. (I don't have the data I took from my experiments, it was several years ago, so can't tell you just what input impedance results from using only two on each side.) But perhaps with use of a VNA (I use the DG8SAQ VNWA that can have output power reduced so the loop amp isn't overloaded), you could find a different input transformer turns ratio that would work using the reduced number of jfets. That would be quite an interesting experiment to do!?? :)

73,

Steve AA7U

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Steve,

?? thanks. Well, I am interested also in VLF, so maybe I should try to get hold of some 2SK932, though the idea of working with SMDs is not appealing (but I have already done that in the past). I also have one of the inexpensive nanoVNA, so maybe I could do some tests.