[RFI] external noise source identification
Dave Cole (NK7Z)
dave at nk7z.net
Fri Dec 21 18:43:05 EST 2018
Grab an AM radio and see if it is there, if so, use the loop to locate
it... If not, build a 2 or 3 foot loop and start hunting...
When you do ID it, I would be most interested in what it is, and a
capture of it alone for my web page of RFI sources at:
I don't see anything like that in the captures at all...
73s and thanks,
Award Manager, 30MDG Grid Contest
ARRL Technical Specialist
ARRL Volunteer Examiner
ARRL OOC for Oregon
On 12/21/18 2:19 PM, bill K7WXW wrote:
> GA All
> My noise reduction project continues. I have been working on noise
> sources in my house
> but need some help with what seems to be an external source.
> For data capture, I am using an RSPro2 and RSP-SAS spectrum analyzer
> software, running on a
> battery powered laptop. The RSPro2 SDR is connected, via window line, to
> my main antenna through the
> high Z port.
> I ran four series of data capture:
> SDR with nothing on any antenna port (establishing a base line, looking
> for artifacts).
> SDR with 2' of window line connected to the high z port
> SDR connected to my main antenna, house power and fiber modem power on
> SDR connected to my main antenna, house power and fiber modem power off
> Each set includes captures at 3.25, 7.15, 10, 14.15, 18.00, 21.00,
> 24.50, 28.50,
> and 29.50 MHz, all using the same SDR and SA settings.
> As expected, some of the noise is produced inside my house (modems,
> switching power
> supplies, etc). I am cleaning that stuff up by switching out supplies,
> adding ferrites
> and so on.
> But there is a lot of noise between 2 and 6 MHz that is present whether
> my QTH is powered
> up or down. That's what I want to focus on in my request for help. I've
> posted six
> screen captures that show what is happening, which can found at this
> dropbox link:
> The first four show a 500KHz span around 3.25MHz. The first three are
> all with
> house power on, the last with power off:
> 003 K7WXW RFI 122018
> - window line feed, 2' (evening)
> 001 K7WXW RFI 122118-1
> - window line feed, 2' (morning)
> 001 K7WXW RFI 122118-2 (AGC was accidentally switch on for this set of
> - 130' doublet (main antenna)
> 002 K7WXW RFI 122118-3
> - 130' doublet (main antenna, power off)
> The last two two show a wider span, with house power off:
> 015 K7WXW RFI 122118-3 (5MHz sweep, centered at 4.05MHz)
> - 130' doublet (main antenna, power off, fiber power on)
> 016 K7WXW RFI 122118-3 (5MHz sweep, centered at 4.05MHz)
> - 130' doublet (main antenna, power off, fiber power off)
> Whatever the source, it is powerful enough to pick up with a 2' section
> of window line
> connected to an SDR in my basement. It doesn't change when I power down
> the house and
> fiber modem. It appears to be going 24 hours a day, though I haven't
> gotten up in the
> middle of the night to confirm that. Any ideas where to start looking?
> thx and 73 Bill K7WXW
> brevity is beautiful.
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> RFI at contesting.com
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