[RFI] need ideas on hunting down QRN-like noise source
Scott Ginsburg
k1oa at comcast.net
Tue Jun 15 19:11:37 EDT 2004
Eddie,
EDWARDS, EDDIE J wrote:
> Nothing at all above 24Mhz? And nothing at all below 7 Mhz?
> Or is that just the range of your antenna system?
I never hear it above 24 MHz. I *may* be hearing it above
7 MHz but I wonder if on 80M I'm hearing real atmospheric
noise and not my noise. On 40 I'm pretty sure it's my noise.
I also have a lot of other man-made noise on 80M.
I'm using a log periodic for 20-10M and a 2-el beam for 40M. My
80M antenna is a single element delta loop at 50'.
> You said two noises; have you heard one without the other? Or always
> together?
My other noise is a whole different story - that one I think I
may have located the house it's coming from, but more sleuthing
is required. I believe the 2 are unrelated.
> What time at night does it go away? 10 or 11pm? After midnite?
I haven't taken samples much past 11:00 PM so I don't know when
it subsides. It is typically still active at 11:00 PM. I'll try and see
what it's like at 2:00 or 3:00 AM one of these nights.
> It sounds like it might be some sort of device (Part 15?) in someone's
> home in the neighborhood. Particularly due to the times involved; it
> sounds like it's associated with a human's activity schedule versus
> non-human events like the weather. It doesn't sound like it would be
> powerline noise, although if it is conducted from some distance away,
> you might get that freq range due to some weird resonance effect. It
> does follow electrical system loading somewhat (although it should peak
> in the morning and then again after work--not at noon).
>
> Since you have noted the direction it's coming from, get a map and plot
> a line in that direction. Then go mobile targeting streets along that
> bearing. Once it gets stronger, find the freq it peaks at, then go
> higher to see if the freq range has changed. If so, go to the highest
> freq at which you can still copy it. Then keep following the bearing
> and tuning higher until you're into the VHF high-band (2-meter or
> higher). Then go portable with an VHF AM-mode radio like an Air-band
> radio.
I've already plotted a line and driven the streets along and near that
line, for up to 2 airmiles from my house. I heard no peaks anywhere.
> If the freq range stays the same, then it's probably a specific device
> in a home. Tune to the edge of the freq range where it's weaker and
> continuing to hunt will help you close in on its location hopefully.
The intensity per band definitely changes. Some nights I hear almost
nothing on 17M, others it's almost as loud on 17 as it is on 20M.
> Good luck!
Thanks for the ideas.
73,
Scott
More information about the RFI
mailing list