[Elecraft] dynamic range questions

[Bill W5WVO]

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 <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
>
>
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