Topband: Spur as it reappeared

[Eric Scace K3NA]

   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 at 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 at yahoo.com>
> To: "Rick Stealey" <rickstealey at gmail.com>
> Cc: wd8dsb at aol.com, "donovanf" <donovanf at 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 at 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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