Geoffrey Mackenzie-Kennedy wrote:
A receiver with a "weak" cascade following the IF filter might appear
to be be a good performer based on tests done this way, but will
probably fall apart when two or more strong signals enter the IF
filter's passband.
Well... yeah,sure. That's why the K3 offers a selection of appropriately
narrow roofing filters at the 1st IF frequency. If you're trying to copy CW
with the 6 kHz AM filter inline, of course you're going to have problems, just
as you certainly do with all the up-conversion radios (like the TS-2000 I own)
with broad-as-a-barn-door roofing filters in the 1st IF. Strong off-frequency
signals within that wide passband will cause later stages to fall apart, no
question. That's why the K3 (and a few other radios like the Orions) are
designed the way they are -- to do everything possible to mitigate against
that possibility.
Bill / W5WVO
During the development of high performance
receivers common practice in my experience was to employ multiple
signal tests, two tones in the IF passband and one or two placed on
the skirts. I am aware of suggestions that have been made during the
past years regarding these test procedures used to evaluate amateur
receivers, likewise to restore proper useage of the term MDS which is
another story :-)
73,
Geoff
GM4ESD
Curt Milton <[EMAIL PROTECTED]> wrote:
Mike
for two tone dynamic range testing, both signals are
located intentionally outside the detection passband
(narrowest filter) of the receiver, and the receiver
is tuned so that one of the third order intermods is
within the passband.
you may find that this is a useful reference:
http://www.arrl.org/tis/info/pdf/109435.pdf
when the measurement is bounded by phase noise, it
means that instead of introducing a distortion product
or reducing the level of a weak signal, instead the
phase noise introduced by the receiver itself
(generally the local oscillators) has degraded
detection of the weak signal.
otherwise, you seem to be on the right track with your
understanding.
73, curt
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