> Hi Tree,
>
> N6TR wrote:
> >IMHO (getting really brave jumping in here - so emphasis on the H),
> the "in band" IMD is a very important feature when using a receiver
> that will be dealing with lots of noise (like Topband).
>
> >Think of noise as a bunch of little signals in your passband. Think
> about how the signal you are trying to receive interacts with that
> noise (which is about the same strength - right?).
>
> I've never paid much attention to that test since it is mainly
> intended as a test for internally-generated SSB splatter. I think there
> could be 2 flaws in your assumption that the test may be a good
> indicator for noise floor CW interference on 160.
Well, here is where we start getting into a debate more similar to
the golden ears of high end audio.
There are many people that I know who feel that some of the specific
radios out there sound very poor when they are being called by
hundreds of stations (typically while operating at a DX location).
When enough signals fill up their passband - the audion sounds "muddy".
There are radios that seem to work better than others in this regard.
The TS930 is a good one, so is the TS50 of all things. Some of the
higher end radios are not so good - the MPs, TS850s are two examples.
So - I think there is an audio quality component to this situation as
there is when when receiving a SSB signal.
Perhaps someone smarter than me can explain this from a mathematical
perspective - where we have all of these little signals 35 db down
filling up the passband when you have 100 signals in it - and all
of them are about the same strength. The case of two signals is
pretty simple to imagine, but when you have many of them - all beating
against each other, each generating 6 or so products, it is much
harder to comprehend.
Tree
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