[R-390] r390a CHOKE L502

[Jim Haynes]

Yeah, if you had been around last August I was dealing with the same
problem.  I found a 12 mh inductor in the Mouser catalog and used
that as a replacement and the overall gain test came out fine.

Now I had a lot of discussion with another list member who believes
that the 12 mH toroid originally used is self-resonant around 455
KHz, whereas the one I used is self-resonant at a somewhat lower
frequency.  I'm still skeptical that the frequency of the toroid is
that high, because it works out to an awfully small amount of
distributed capacitance, especially when you consider the output
capacitance of the tube it is feeding.

One thing we both thought of is that Mouser has some parts with lower
inductance and higher self resonant frequencies, so you could use
several of those in series to get both the desired inductance and
the desired self resonant frequency.  Since the 12 mH part seems to
work satisfactorily I didn't pursue that any further.

Jim W6JVE



jhhaynes at earthlink dot net