Saturday, November 22, 2008

The Noise in my Head

Here are some audio clips of the noise I hear at my QTH:
  • The typical broadband noise I hear most of the time. This was recorded 0830 local time, Nov 22, 2008 on 7030 kHz, and had a signal level of S9. This noise is present on 1.8, 3.5, and 7 MHz. It is absent on 10MHz and above.
  • An S9+20 dB noise burst, 1.3 seconds in length. I hear these frequently in the evening. Recorded Nov 19, 2008 on 7022 kHz at 1900 local time. Unknown what bands other than 40M this appears on.
  • A narrowband signal, several kHz wide, S8, on 3515 kHz. This is pretty obviously some piece of consumer electronic equipment, probably in my house, or in our closest neighbor's house. AHA! It's our new Series 2 TiVo. Interestingly, our older TiVo, which we still have, does not cause this RFI.
  • A fairly clean carrier that repeats about every 69 kHz across the 20 meter band. This turns out to be our Xantrex Grid-Tie Inverter for our solar energy system (turn off the inverter - carriers go away). It's S9 on the G5RVjr, which is close to the PV array, but a few S-Units lower on the 40M vertical. It's definitely a problem, but I consider it a lower priority since a notch filter could null it out (note to self: need a radio with a dedicated knob for the notch filter, or an auto-notch DSP).
  • An S9 noise across all the 80 meter band with peaks every 60 Hz. Audio spectrum:

    Walking around with a portable shortwave receiver, I think I've located the house that's the source (one of our neighbors), and at first thought it might be their fluorescent porch light. I just happened to be listening this evening and the noise stopped abruptly at 10:20pm local time. I checked, and the porch light was still on, so that's not it. Coincidentally, our other neighbor's sprinkler system turned on at the same time. Probably unrelated, but I have heard of sprinkler systems being RFI sources.

    Around 11:00pm local time, I started to hear the noise again, although its signal strength was much lower. When I walked around with the portable receiver, the signal seemed to be mostly absent where it was before, and was much louder near the neighbor's house with the sprinklers. So I'm really not sure what's going on with this.
Well, two sources identified.

I also plan to start keeping a log of when I hear these, so I can try to correlate them to their source.

1 comment:

Anonymous said...

I also have the normal broadband noise that you have recorded. On 80 meters it is about S5-6 during the say and S9 at night. I am using an inverted vee with a choke balun at the feedpoint (based on K9YCs writings). I will watch your blog with interest to see what you find out. Harris K9RJ