Jim,
You have correctly assed and describe the relative performance of the Inrad vs.
TT filters. My lab.
assessment is attached!
The attached µSoft Word file compares the TT #217 (9 MHz/500 Hz/750 Hz offset)
with an Inrad #753 (9
MHz/400 Hz/600 Hz offset). The little blip in the middle of the passband (on
the center frequency
of the trace is not a filter anomaly, rather the tracking generator marker, and
its exact frequency
is
displayed in the TG digital readout to illustrate how the filter centers about
that frequency). The
scan is 200 Hz/division.
Note the anomaly with the TT #753 when installed in a VI Opt-3 or VI+. This is
due to the
construction of the Inrad filters, and Inrad is aware of this. They do not
separate the input side
ground from the output side ground, as is done in the TT filters, and when
installed in a VI/VI+
there is a minor ground/ground loop problem. However, the anomaly is 50 dB
down on the low side and
60 dB down on the high side skirts, and in normal ham operation, the human ear
cannot discern this
anomaly. IMHO, it is a "no problem".
73, Dave, K1FK
Fort Kent, ME
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