I've been hearing a curious noise on 40 (and 17) meters at my home in Northern California near Sacramento. The noise seems pretty much the same regardless where on the band I'm listening. I first thought it was something local until I heard someone else make passing reference to it. I started by noting when it was heard. I then set up to record the audio off my receiver. The noise appears once and then is over until the next time. The links to the .wav files are within the table. The files were recorded in LSB (USB on 17) with a bandwidth of 3.6k in and outside the amateur band.
Looking at the individual 'chirps' it appears that they consist of two parts, .04 seconds in duration each, separated by .015 seconds of silence.
I have also heard single bursts that one would ignore if not actively listening for them. At this point I haven't bothered to record them (except #7) because they seem to come at random, at least at this point. If you have theories or have heard the same thing on this or other bands please send information to steven AT k6bz DOT net.
15-Feb-05 I haven't heard it on 40 for quite a while now. I hear it on 17 occasionally, but not as often as I did on 40.
New 18Mhz 1
New 18Mhz 2
New 18Mhz 3
New 18Mhz 4
This is a good one. It started out with three beeps as in recording #1. I started recording about two seconds into the sequence. As you can hear the pulses frequency increased as time passed.
|Frequency||Time UTC||Date||Sound Link|
|7.0430||1700||11-12-04||partially recorded #2|
|7.2685||2041||11-12-04||five minutes after single burst at 2236|
|1655||11-14-04|| recorded #5
It sounds like there are three 'chirps' sent at 5 seconds and at 19 seconds near noise level (you may need great speakers to hear). The rest comes at about 60 seconds.
|1708||11-14-04|| recorded #6
Exact same settings as above but with much different sound quality.
|7.2940||0043||11-17-04||Heard by two other listeners on a net. They were about 80 miles and 450 miles from me.|
|7.4940||1815||11-17-04|| recorded #7
Recorded two 'chirps' first at about .6 sec into the file, the second just slightly over 60 seconds later. This file is a sample of the last 'chirp' played three times then slowed by a factor of 50% for several generations to show the digital nature of the signal.
|7.2940||0259||11-20-04||Smack dab in the middle of a net and no comments.|
|7.0622||1530 - 1535||11-23-04|| recorded #12
Five minutes earlier I heard this single chirp @ 1530. Same settings on both recordings.
|7.3090||1840||11-24-04|| recorded #14
Seven minutes earlier I heard this single chirp @ 1833. Same settings on both recordings.
|18.127||1537||11-26-04||I thought I have have heard this outside 40 meters, but today is the first time I noted exact circumstances.|
|18.1629||2337||01-16-05||I thought I had heard a couple of single chirps while checking out the 40m swap net today. The is the first time in a while that I've heard the entire set. I had the radio on listening to static while writing an email.|
|18.1385||1705||02-08-05||First one in the last couple of weeks.|