On Apr 29, 8:58 am, "Harold E. Johnson" wrote:
Hi Harold,

Well, I'm curious about -61 too. Turns out I have some FT50-61's (or
so claimed by Baggy Bob...), and I have FT50-67, FT50-68, FT50-43,
T50-1, T50-2, T50-3 and T50-7 to try for comparison. Unfortunately,
we're out of T50-6, but maybe I can arrange a test on a different -6
against the same size -2, at least. Not sure if I'll get to the coil-
winding and testing today, though.

Cheers,
Tom

Well, if you're going to put it off, I can send you a few T50-6's. Probably
some -10 material too. BUT! I want your results when you get them! If you
have them in a filter, would need to know the operating Q as well, but if
just the toroid itself, wonderful to have.

W4ZCB

Sure, I'll test 'em. I'll go ahead and test what I have, and add the
-6 in when I get them. I have the test setup documented well enough
that it will be easy to repeat the same tests later. Of course, the
test is always with some particular test setup. Even if I just
connected the toroid shunt across a 50 ohm line with source at one end
and analyzer at the other, it's still a particular environment, and
the results will be different if, for example, I add in my 1MHz
bandpass filter at the generator output (to kill generator harmonics)
and add my 1.5MHz HPF at the analyzer input (to kill the 1MHz so the
analyzer can be set to a lower range without contributing significant
distortion of its own). Each of those filters changes the source or
load impedance. I suppose I could have made diplexing type filters
that maintain a constant impedance vs frequency, but these guys are
big enough as it is, using high Q air core coils.

Anyway, the particular environment I chose for the coil test is in a
simple high-pass filter, nominally third order 0.1dB ripple Chebychev
with a 1MHz -3dB point: 2.2nF series, 5uH shunt (coil being tested),
2.2nF series. The distortion products I'm reporting are all 2MHz and
above, where the output capacitor passes things with very little
attenuation, and the excitation voltage across the inductor for a 1MHz
input is about 1.7dB higher than the 50-ohm source indicated output.
I suppose I could make the test more interesting by exciting a high
circulating current in the inductor, but it seems like if I excite
them in the test circuit to where distortion is clearly measurable,
the relative results be a good indication of relative performance in
other circuits.

Cheers,
Tom