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 <[email protected]> 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" <[email protected]> > To: "Rick Stealey" <[email protected]> > Cc: [email protected], "donovanf" <[email protected]> > 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 <[email protected]> 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> >> > _________________ > Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _________________ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
