[IRCA] Propagation and DX differences

["Craig Healy" <bubba@xxxxxxxxxxxxxxxxxxxx>]

> >I have to wonder just what the difference in solar and other conditions
were
> >back then, or if it's entirely due to lesser interference in those days.
> >I'd think the improvements in antennas and radios would almost negate the
> >increased levels of current interference.  Thoughts?
>
> Perhaps you can help answer this one, Craig.   Like Patrick,
> I can recall some pretty incredible DU's in the 80's...
> (snip)
> My impression is that domestic splatter has worsened considerably
> since then (stations were already NSP by then).  From your experience,
> has modulation level / splatter increased since the 80's, and if so,
> by how much?

I think it has decreased.  I remember overmodulation being rampant because
audio processing was still quite crude and unfiltered.  Audio was fed in up
to 15KHz, and not filtered at all.  These days even a 10KHz audio bandwidth
is still somewhat uncommon.  Usually less.  Today's processors have brick
wall low pass filtering.  For example, the local 550 station has negative
peaks just slightly under 100% and positive peaks approaching 124%.  Yet I
can hear the 540 and 560 stations just fine.  I have even heard the 560
station in Springfield, MA while parked at the 550 transmitter site.  I have
set the low pass filtering to about 6KHz to match what most analog radios
pass these days.  Never a complaint about muddy audio.  Other locals as
viewed on the SDR-14 are 10KHz or less, not counting the IBOC critters.

In 1975 we used state-of-the-art processing on 550 and it splattered +/-
20KHz or so.  Quite messy, even though it really wasn't overmodulated.
Overall, I'd have to say splatter has decreased in this area.

> But propagation must have contributed also.  Recent years have seen
> some pretty good East Asian conditions here compared with what I
> remember from the past, even if domestic splatter has increased.

When I get some time, I have to do some Google work...

Lessee...  In baseball, out of season conversations are called the Hot Stove
League.  What shall we call summer DX discussions?  The Cold Brew League?

Craig Healy
Providence, RI


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