[Lowfer] TAG WM SIW in CT

[stanw1le at verizon.net]

Hello Dex.
I was having problems copying 474.2 KHz with high ambient noise centered in the AM band at 570 KHz.Noise showed up as 120 Hz rich harmonics.
I originally suspected seasonal Christmas lighting in the neighborhood.
But I had started an experiment/project on the RF work bench using a GPS/DO, 10 MHz distro box, HP synthesizer and HP counter (11 digits worth) to generate a LO for a 30M TX block downconverter to 474.2 KHz.All of that equipment had worked well previously, so I did not suspect them.
Turned off selected items in the shack, LED lamps, laptop, overhead LED lamp......  no change
turned off other selected items in the home, variable LED can lights, cable internet modem..... no change
Got in the truck and monitored 570 KHz AM on the truck radio,  still theredrove around the street.... noise went away.... it was strongest at my QTH   !!
Went back home and turned all AC power off at the main 200A breaker..... noise went awayRestored AC power and the noise came back.
Got out the portable IC-705 with a whip antenna and started sniffing the AM band at 570 KHzstrongest in the shack on the RF work bench.
Powered OFF a 10 MHz station GPS/DO reference distribution box.... noise went awayApplied DC to the distro box again and noise returned.
Replaced the 10 MHz distro box with a spare, powered it up and noise came back.
Replaced the wall wart, 12V at 1A switcher, and the noise went away permanently.

Lesson learned: you can be your own worst enemy, do not trust switching power supplies




Stan, W1LE    FN41sr    Cape Cod


























ZZZZz

 

    On Thursday, January 16, 2025 at 08:14:46 PM EST, W4DEX <dexter.mc at gmail.com> wrote:   

 The watering hole here is totally wiped out by what sounds like switching
power supply noise.
2200M is clear, so I have been running WSPR only seeing K9KFR.  Also some
longer duration transmissions that I suspect are FST4W but have been unable
to decode.

Dex
______________________________________________________________
Lowfer mailing list
Home: http://mailman.qth.net/mailman/listinfo/lowfer
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Lowfer at mailman.qth.net
Post must be less than 50KB total for message plus attachment!

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html