[RFI] external noise source identification
wd8dsb at gmail.com
Fri Dec 21 21:01:39 EST 2018
You show these repetitive signals on your SDR setup, but need to make sure
they are real.
1) Do you actually hear each of these repetitive signals on your HF rig
versus the SDR receiver?
2) If you reduce the SDR system gain, do the spikes suddenly disappear (do
they suddenly appear when you increase your SDR gain past a certain
point)? It's very common that when SDR gain exceeds a particular value
that spurious emissions appear in the SDR display.
3) If you go outside away from your house with your SDR system, are these
signals still present?
Note: I run a portable SDR DF system with a lap top, and the battery
operated lap top (a Dell high end lap top) generates lots of RF hash that
can be detected when my portable DF antenna is within a few feet of the
On Fri, Dec 21, 2018 at 5:19 PM bill K7WXW <K7WXW at qrpdx.org> 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.
> RFI mailing list
> RFI at contesting.com
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