[GreenKeys] scope

[Jack]

ZCZC

The Fleshers and later HAL's use active filters which always gave
a nice sharp scope pattern (usually a straight line). The toroid
filters are inherently wider, thus the thin elipse, and also
subject to
ringing, phase shift, low Q, etc. Circuit parameters also affect
the
interaction between the filters, thus adding more to the
distortion in the scope pattern. Whenusing multi-section toroidal
filters, as discussed in the original TT/L articles, the
filtering/performance is better, obviously, and the scope pattern
is
much more of a line or very thin but straight elipse.
You shoud see the patterns from the horizontal oscillator
tunable coils used in the very first TU's, like the Twin
City TU and the W2PAT and W2JAV models; looked like
two footballs! But they worked...
My first TU, a Twin City Tu, had one filter and it was a
tuned audio output transformer secondary...I was 13 at the
time, what did I know? But, it worked, too. After mowing
a few lawns, I was able to afford two toroids, which Byron, W2JTP,
personally tuned for me!

73,
Jack WA2HWJ

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