To George’s point: This site is definitely in the complex category. Both
stations change patterns between day and night, meaning they have a lot of
(expensive) phasor hardware and high-current switches. The times when pattern
and power level changes must occur are specified in the station license data on
the FCC website, and change monthly. A station has 3 minutes to complete the
changeover.
Frank: It has become increasingly common for AM stations to share sites as
the value of urban real estate escalates. In fact the WWRU/WKDM site pattern
switching and diplexing arrangements were built by Kintronic and feature in
their brochure
<https://www.kintronic.com/wp-content/uploads/2016/01/QF-723-019-Rev.-B.pdf> on
multiplexing AM/SW sites. There is at least one directional site that is
quad-plexed with four AM signals at non-trivial power levels, with all stations
changing patterns between day and night. These designs are not for the faint of
heart — but super-interesting.
I am responsible for two diplexed non-directional AM sites around
Denver-Boulder: KGNU/KKCL in Englewood (adjacent to Denver) and KVCU/KCFC in
Boulder.
— Eric K3NA
> On Jan 6, 2023, at 16:44, Frank W3LPL <donovanf@starpower.net> wrote:
>
> Hi George,
>
> Faulty day/night switches may well be the cause! You may have seen
> in my previous email that both stations switch patterns from day to night.
>
> This is the first time I've ever hears of two AM stations with two
> antenna arrays sharing the same small site
>
> 73
> Frank
> W3LPL
>
>
> ----- Original Message -----
> From: "George Hirst" <geohirst@yahoo.com>
> To: "Rick Stealey" <rickstealey@gmail.com>
> Cc: wd8dsb@aol.com, "donovanf" <donovanf@starpower.net>
> Sent: Friday, January 6, 2023 11:39:10 PM
> Subject: Re: Spur as it reappeared
>
> I am “talking through my hat” here. The fact that it seems to suddenly get
> much stronger right about your (New Jersey) sunset make me wonder if it is
> related to the AM broadcast station(s) changing their antenna pattern(s). (I
> haven’t done the research to know if these stations are ones that are
> required by the FCC to change their patterns at night to “protect” more
> senior stations who share the sane frequency.) Perhaps there is some
> corrosion on the RF switches employed in that function that introduces
> nonlinearities. Those nonlinearities result in mixing products (ie. 1940 kHz)
> which are then radiated. ????
>
> George - WF4U
>
>> On Jan 6, 2023, at 4:14 PM, Rick Stealey <rickstealey@gmail.com> wrote:
>>
>>
>> Note the waterfall. The timestamp on the right is accurate. The horizontal
>> line is a lightning burst. But notice the ugly signal that came up on 1940
>> before the carrier. Anyone have any idea what is happening there?
>>
>> <image.png>
>>
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