Whence the nighttime interference on 1030?

[Garrett Wollman]

<<On Thu, 14 Feb 2019 15:18:46 -0500 (EST), Rob Landry <011010001@interpring.com> said:

> 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.

...in the low-ground-conductivity northeast.  It would be pretty
terrible in Iowa or South Dakota where 300 miles is the norm for a
signal-limited 5-kW ND.

-GAWollman