[RFI] Splatter from AM Radio Station WNTS Indianapolis and Resolution

[Don Kirk]

Late last year I stumbled upon a sick AM radio broadcast station in
Indianapolis (WNTS, 1590 KHz) while driving to a hams QTH to track down
some powerline noise.  The station was generating splatter all the way up
into the 160 meter band which was causing problems on 160 meters at Mike's
(W9RE) QTH.

The AM radio station's Chief Engineer invited me to the transmitter site to
work with him and a contract RF Broadcast Engineer on the problem (both of
them are hams).  The problem turned out to be bad capacitors in the "Pulse
Duration Modulator" which is really a pulse width modulation (PWM) system.
It took almost 10 months for the replacement capacitors to arrive and for
the repairs to be completed.  The transmitter was finally fixed earlier
this month, and in the meantime the transmitter was running at reduced
power to limit the splatter.

Today I created a simple website to document the case, and here is a link
to the website for those interested:
https://sites.google.com/view/wnts-rfi/home

Here is a link to a youtube video recording the splatter when I originally
stumbled upon it and this link is also on my website mentioned above:
https://youtu.be/VaunFwVAyUI

Just FYI, and 73.
Don (wd8dsb)