Hi Frank, everyone —
One does not need another person to be harmed by the intermod on 1940 kHz
AM broadcast regulations include a very strict bandwidth mask for any form
of radiated spurious signal more than ±75 kHz from the carrier frequency. At
these power levels, such spurs must be less than -80 dB below the carrier
(measured at a point about 10 wavelengths from the center of a directional
array, usually in the main beam).
There are very specific measurement procedures to be followed for
compliance. Every AM station is required to measure — and retain a report of
compliance in their station transmitter logs — annually (no more than 14 months
between measurements). The measurement procedures require some care, a very
good spectrum analyzer, and a calibrated antenna.
If the station is out of compliance, it has 10 days to return to compliance
before notifying the FCC. If the problem cannot be repaired within 28 days, the
station must obtain an STA to continue operations.
===
Now, as to the identity of the stations. The FCC’s AM Query
<https://www.fcc.gov/media/radio/am-query> webpage is invaluable for
researching issues like this.
Rick identified one audible program as from WWRU. WWRU operates 10 kW
daytime with a 2-tower directional array at 40° 49' 13.36" N 74° 04' 02.51” W.
The tower registration numbers are 1040103 and 1242403. At night it runs 10 kW
into a 4-tower array
A search of AM stations within 3 km reveals, as reported by others, WKDM on
1380 kHz. [Note: Be careful using AM Query’s “radius around a lat-long” search
tool, as the input must be in NAD-27, not NAD-83 coördinates.]
WKDM uses a 3-tower directional array (daytime) at the same coördinates, and
a 4-tower directional pattern at night. Tower #1040103 is shared by both
stations. That means a diplexer is employed to combine the signals into this
tower — and would be the first place to look for generation of a mixing product.
===
What to do?
Both stations run 10 kW or more. On that basis alone, the chief engineer of
each station is required to be an employee of the station — not a contract
engineer. (The same requirement applies to any AM station running a directional
pattern.) That means the chief engineers will be easy to contact — just call
the station’s main phone number. WKDM’s website is here
<https://www.am1660.com/>, and info@am1680.com <mailto:info@am1680.com> is the
general email address. +1-718-352-1660 is the phone number at their
headquarters location.
If this is unsuccessful, one can escalate to the points of contact
registered with the station license. In this case, a search of the FCC LMS
database reveals both stations are owned by the same company and have the same
points of contact:
seank@mrbi.net <mailto:seank@mrbi.net> … and the legal representative is Mark
Lipp at lipp@fhhlaw.com <mailto:lipp@fhhlaw.com>
If no satisfaction has been obtained, anyone can file a complaint with the
FCC Enforcement Bureau explaining that these two stations are operating out of
apparent compliance, with the support data and information about how the
station management has been unresponsive. The Enforcement staff maintain
contact numbers for each station to use in cases of emergency, and will follow
up (as I have personally witnessed).
I hope this helps.
— Eric K3NA
> On Jan 6, 2023, at 18:03, Frank W3LPL <donovanf@starpower.net> wrote:
>
> Hi Fred,
>
> We've figured out the mystery, now we need to determine if anyone is
> being harmed by the weak, intermittent intermod on 1940 kHz
>
> 73
> Frank
> W3LPL
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