Whence the nighttime interference on 1030?

[Kevin Vahey]

Rob

The best example of this is the New York Thruway at night - WBZ at night is
iffy between Albany and Utica at night but west of there it is a local all
the way to Chicago.

An hour before local sundown in Chicago, WBZ is as clear in the Loop as any
of the Chicago AM stations.

On Thu, Feb 14, 2019 at 3:20 PM Rob Landry <011010001@interpring.com> wrote:

>
> The most likely cause of interference to WBZ is WBZ itself. There are two
> types of emissions from AM stations: a surface wave, which follows the
> ground, and a sky wave, which follows a straight line into the atmosphere.
> When it hits the "D" layer of the ionosphere it is absorbed and
> disappears.
>
> However, the "D" layer is only present during the day. At night it
> disappears, and the sky wave continues until it hits the "E" or "F" layers
> of the ionosphere, which reflect it downward. That is why people hundreds
> or even thousands of miles away can hear WBZ at night, but not during the
> day.
>
> WBZ's surface-wave coverage is very impressive; driving to visit my father
> in upstate NY a few years ago, I had a listenable signal from WBZ all the
> way to Schenevus, NY, on I-88 just short of Oneonta. That's about 150
> miles, all of it over land -- excellent for an AM staion in daytime.
>
> If you live at the outer edge of WBZ's daytime coverage area, you will
> often receive both the surface wave and the reflected sky wave, and they
> will interfere with each other. In the worst case they can completely
> cancel. If they do, you'll hear anything else that happens to be on 1030
> but not WBZ.
>
>
> Rob
>
> On Wed, 13 Feb 2019, Doug Drown wrote:
>
> > I live on the upper midcoast of Maine, where WBZ's daytime signal comes
> in
> > like gang busters --- absolutely crystal clear, no hiss or interference,
> as
> > though the transmitter were just down the road.  One the sun sets,
> however,
> > it deteriorates rapidly, especially at this time of year.  What is/are
> the
> > station(s) I'm hearing on 1030 kHz?  They seem to interfere with one
> > another, such that I can't make anything out plainly.  Am I correct in
> > thinking that 'BZ's signal is nondirectional?  If so, the presence of
> these
> > other stations' signals surprises me.
> >
>