40 Meter interference

Trucker

This just showed up in the last three weeks. I have disconnected the antenna and it goes away. It is the strongest on 40 Meters. On other bands, the noise floor rises, but no noticeable interference. I am thinking it might be grow lights. It sometimes stays on for hours at a time, and other times, it goes completely away for days at a time.

I have shut down power completely and powered my radio from a car battery and still it shows up. I have attempted to use a handheld shortwave receiver tuned to 40 meters and walk around my house and a few of the neighbors. It's loud, but, i still cannot pinpoint it.

Any ideas what it might be?

James

WD5GWY

KD0RC

Hi James, one thing to try is to zoom all the way out so that you can see 7MHz of the spectrum at once. Scroll the panadapter so that the display starts at 0 Hz. You should see about where the fundamental of the crud is. It may be hard to discern if it originates in the broadcast band or anyplace where there is already strong signals. That might give a clue as to what is causing it. When you zoom out like that, "WIDE" will appear on the upper right hand side of SmartSDR. A ton of junk that the 7th order filters of your 6600 normally filter out will become quite evident.

Trucker

Thanks Len, I will give that a try.

It could be broadcast band interference. I did have that several years ago with my 6500. I could actually listen on the AM station's frequency on my portable and watch 80 meters hop up and down as they talked. I called the station and told them what was happening. (the broadcast tower is about 6 miles line of sight from me ) and the station engineer did some checking and found a bad connection on the antenna. ( 50,000 watt station) He fixed it and the interference went away!

This could be that, but, it was not quite like what I am experiencing now. It is a hissing sound. (best as I can describe it)

James

WD5GWY

AKA Trucker

Wayne VK4ACN

Could be anything, but my neighbours recently installed 3 ceiling fans, and the interference looks similar. I get it on 20-15 and 10m.

Trucker

I figure it will be next to impossible to find. It went away again early this morning and so far, all is quiet on 40 meters again.

James

WD5GWY

AKA Trucker

John KB4DU

The way it wanders in frequency it’s probably a switch mode power supply of some sort.

Trucker

It was gone most of 2 days then returned. I followed Len's advice and zoomed out enough ( about 14 Mhz ) and the peak of the interference centers around 7 Mhz.

I figure one of our neighbors has some new device causing this. But, tracking it down seems nearly impossible. Thankfully, the WNB beats it down ( but doesn't eliminate it ) to the point I can carry on a QSO. The waterfall really helps in this case as real signals are easy to see from the wiggly lines the interference makes.

Maybe whatever it is will give up the ghost someday!

James

WD5GWY