Topband: AM broadcast multiplexing

[Eric Scace K3NA]

Being so close to the transmitter site. it's quite possible that you are experiencing receiver front end overload, and your receiver is generating some of these signals.

You might wish to try the AM “brickwall” filter <https://www.qsl.net/wb5wpa/Filter/AM%20Brick-Wall%20160%20Meter%20Filter.pdf>. DX Engineering sells them for $195 <https://www.dxengineering.com/parts/dlw-fl1718>. I have used one in many measurement situations at locations even closer than yours — it’s quite effective in knocking down AM broadcast signals to a level that eliminates receiver overload and internal IMD product generation.

— Eric K3NA

> On Apr 21, 2023, at 10:16, Phil Lefever via Topband <topband at contesting.com> wrote:
> 
> Eric,
> 
> I live about 3/4 mile from the multiplexed stations KKMS/WWTC (980 & 1280) here in MN and they are all over the ham bands in my receivers.
> 
> https://www.radioworld.com/tech-and-gear/tech-tips/wwtc-moves-in-with-kkms
> 
> Luckily it isn't such a problem on 160m, just the 2nd harmonic of 980 at 1960 is the only real issue and I seldom operate high in the band. I do have a Morgan systems AM bcb filter in place.
> 
> The real issue I have is at 3540 where the 2nd harmonic of 1280 mixed with 980 to give me a healthy S9+20 signal with intelligible modulation. Pity this is in the heart of 80m allocation.
> 
> I have had contact with Mark Persons and the station engineer. They even measured interference levels in my driveway and alas they are within specs. Shame that I am just too close. I feel bad for one other ham that is about 150 feet from the ends of that stations radial field!!
> 
> Kind of hoping for the demise of AM broadcasting...
> 
> 73
> 
> Phil, KB0NES
> 
> 
> 
> 
> 
> 
> On Wednesday, April 19, 2023 at 10:03:26 PM CDT, Eric Scace K3NA <eric at k3na.org> wrote: 
> 
> 
> 
> 
> 
> I found the 4-station site: Tri-County in Sauk Rapids MN: 7 towers, 4 stations, all with different day/night patterns. A report is here <http://www.mwpersons.com/articles/2013/four-am-stations/four-stations.html> with photos.
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