[RFI] Broadband RFI...

David Robbins k1ttt at arrl.net
Tue May 31 12:34:03 EDT 2016

The output of any switching supply like that goes down in power as it goes up in frequency... that may be offset by the wires attached to it becoming more efficient antennas so it can be hard to predict.  If it is one of those try going down to 160m and see if it becomes more narrow band.  One of the things I saw was that at the fundamental around 100khz it was 3khz wide, of course every time you double the frequency you also double the bandwidth, so by 160m it was 50khz wide and by 40m it was so wide that it just blanketed the band.  So going lower in frequency may make it easier to detect both because it may be less spread out, but also because the signal may be stronger.

David Robbins K1TTT
e-mail: mailto:k1ttt at arrl.net
web: http://wiki.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://k1ttt.net:7373

-----Original Message-----
From: RFI [mailto:rfi-bounces at contesting.com] On Behalf Of Dave Cole
Sent: Tuesday, May 31, 2016 14:26
To: rfi at contesting.com
Subject: Re: [RFI] Broadband RFI...

On Tue, 2016-05-31 at 08:33 -0500, David Robbins wrote:
> the only difference in hunting a broadband noise is that you have to 
> be sure that when you go from your shack to mobile that you are 
> hearing the same noise and aren't being distracted by a different one.  
> having someone to help you get started who can mark the time the noise 
> starts in the shack while you are listening in the mobile can be 
> useful so you can be sure you are hearing it.
> if it is something like one of the grow light supplies they can be 
> very unstable when they turn on.  look at the spectrum displays on
> 12/13 that show one starting up on my web page at: http://wiki.k1ttt.n 
> et/2012%20Maintenance%20and%20Upgrade%20Blog.ashx#160mrfi   (be 
> patient it may take a few minutes to load as there are lots of 
> pictures on that page)

Thank you for the quick comeback on this!  

Regarding DFing it, you tagged my main fear/issue-- being broadband RFI, with no signature, will it very difficult to correlate it on the mobile rig...  I think I may start, by driving around the area, and taking S meter readings, then put them on a map, then draw contour lines.  That may help me get closer, and avoid the mis-correlations that I am sure will happen... 

Thanks for the images, I can see I need to get the real spectrum analyzer (as opposed to the P3), out and connect it to the antenna and wait...  I am seeing something sweep like mad upon startup, and I suspect it is the same device...  I will see if I can grab a start up image tonight on the P3.

I think I will wait to do this for a few days and pin down the start/end times better first...  

Do you know if these infernal devices have any output on 2 Meters?  If so, is it broadband or is there something I might latch on to?  I could wait for the startup/end, and see once I suspect a location I guess.  

I suspect DFing this one will take some time...

73's, and thanks,
Dave (NK7Z)
For software/hardware reviews see:

RFI mailing list
RFI at contesting.com

More information about the RFI mailing list