[Elecraft] dynamic range questions

[Geoffrey Mackenzie-Kennedy]

Curt,

Would you not agree that a 3rd Order dynamic range test performed with both 
test tones placed outside of the IF filter's passband ,with a product in the 
passband, does not provide a complete measure of a receiver's odd order IMD 
performance but only that of its front end? 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. 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 <wb8yyy at yahoo.com> 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