Peter Chadwick makes a good point:
> Generally, if the distortion is bad enough to be noticed on the signal,
> it's tearing up the band for a long way either side. I've been
> consistently surprised in tests just how bad IMD has to be before it's
> really noticeable on the signal itself.
I often hear people asking others "how does my amp sound?" and
they say, without tuning, it sounds great.
As Peter points out it commonly has to get very ratty with splatter
before anyone, even a local, could detect anything on the actual
operating frequency.
It is quite possible to have very bad IMD and not have any
noticeable audio distortion.
Another problem that masks IMD is local receive site noise, or
other signals, that hide defects.
In my very quiet rural location miles from noise sources, TX phase
noise and IMD shows up easily on uncrowded bands. With a S-1 or
2 background on 160 and 80 meters, my noise floor is often set by
what is transmitting near the DX station...especially SSB stations.
If I lived in downtown Toyko, I'd probably think all current radio
designs are good ones and the DAF was overkill in IMD
performance.
73, Tom W8JI
w8ji@contesting.com
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