With the 2' of ladder line connected, hold both hands on the surface of the
laptop display. If the noise increases (or decreases), your laptop is at
fault.
Dave - WØLEV
On Fri, Dec 21, 2018 at 11:45 PM David Robbins <k1ttt@verizon.net> wrote:
> 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.
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>
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>
--
*Dave - WØLEV*
*Just Let Darwin Work*
*Just Think*
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