[RFI] external noise source identification

bill K7WXW K7WXW at qrpdx.org
Fri Dec 21 21:53:39 EST 2018

GE Don,

Yes I hear them. They aren't like a SMPS or arcing RF audio which is 
pretty easy to identify but it is not quite white noise either.

I am running the system with the gain turned down and the automatic gain 
control turned off. There's no limiting occurring.  I also moved the 
center frequency of the sweep around by adding odd numbers to the base 
frequency (for example, 4.077Mhz) and the repetitive signals remain at 
the same frequency indedpendent of the center frequency chosen.

I have found hash generated by the Dell laptop but it is generally above 
10MHz. I looked at the 2MHz to 6MHz band, where this hash is most 
evidence using two SDRs (an RSP1 and an RSPro2) on a business class Dell 
desktop machine and laptop.

I have not scanned the spectrum while away from the QTH yet. That's next 
on the list.  I did power down the house at the service panel, removed 
the battery from the fiber modem, and checked to be sure that any 
battery powered computing machinery was turned off. The results before 
and after doing so were the same.

73 Bill K7WXW

brevity is beautiful.

Don Kirk wrote on 12/21/18 6:01 PM:
> Hi Bill,
> 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 laptop.
> Don (wd8dsb)
> On Fri, Dec 21, 2018 at 5:19 PM bill K7WXW <K7WXW at qrpdx.org 
> <mailto: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:
>     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 at contesting.com <mailto:RFI at contesting.com>
>     http://lists.contesting.com/mailman/listinfo/rfi

More information about the RFI mailing list