Well, if you can pick it up on 2' or ladder line in your basement it has to be
close. When you power down your house be sure you kill any devices with
batteries like UPS's or battery powered or backed up clocks, tablets, or even
your own laptop. I always wrap the usb cord with a couple of ferrites going to
the sdr as the laptop itself can be noisy.
If its definitely not in your house then take the laptop/sdr and walk around
the outside to see if you can find it stronger in one direction or another. A
handheld shortwave receiver with loopstick antenna can give good bearings on
strong signals.
David Robbins K1TTT
e-mail: mailto:k1ttt@arrl.net
web: http://wiki.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://k1ttt.net:7373
-----Original Message-----
From: RFI [mailto:rfi-bounces@contesting.com] On Behalf Of bill K7WXW
Sent: Friday, December 21, 2018 22:19
To: rfi@contesting.com
Subject: [RFI] external noise source identification
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:
https://www.dropbox.com/sh/zncdt66fdnqb2my/AADSHrTgcV5nJOTVgj1zm6vua?dl=0
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
captures)
- 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@contesting.com
http://lists.contesting.com/mailman/listinfo/rfi
_______________________________________________
RFI mailing list
RFI@contesting.com
http://lists.contesting.com/mailman/listinfo/rfi
|