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In the light of what Evan pointed out about the inductors series resonances in another project, consider the trace below. ? This is the transfer function from the input of the switched low pass filter system all the way to the antenna, when no particular band is enabled. ?
at the time I was making the measurements this didn’t make any sense to me. But now you can see that it clearly shows that there are paths AROUND the filters, and sometimes they are as passable as -25db or so!!! ?This trace should be 2 MHz to 52 MHz so that big spike is somewhere in the low 30 MHz range. ??
That would appear to be a huge problem for the purity of the output signal, right? ?You want the bleed around to be way less than -45 DB.?
if the inductors have series resonances, and the filtering isn’t perfect on powerlines, then signal can get right across. ?Escaping the filters and creating havoc on the output.?
this is another possible improvement
gordon Kx4z?
