On Saturday, March 3, 1990 at 5:52:00 PM UTC-5, John Spencer wrote:
Is this group ever on top of SWL! I logged in just to ask the same questions
about the sweeping signals. It just so happens that I brought home a
.01-1500MHz spectrum analyzer this weekend to investigate the SW bands. I
noticed a carrier that swept up in frequency at a 100kHz/second rate and had a
period of five minutes. Since I live near WWV in Fort Collins, I thought this
might be a service of the NBS. My first thought was one might be able to
determine the wavelength given the time the signal passes the monitored
frequency. There are several different strength signals being transmitted all
a few seconds apart in time. The following is the times the signal was
observed at 16Mhz.

Time UTC

20:45:13
20:46:30
20:46:38
20:46:50
20:47:12
20:48:12
20:49:30
20:49:50
20:51:10
20:51:38
20:52:50
20:53:05
20:53:35
20:54:10
20:55:10
20:56:38
20:57:10
20:58:30
20:58:50
21:00:38
21:01:30
21:01:50
21:02:10
21:03:10
21:04:30
21:04:38
21:04:50
21:05:10

At 6MHz, 11MHz, and 21MHz there was a similar patterns, although at 6MHz the
sweeps were less frequent than those above 10MHz.

BTW If you can get a spectrum analyzer to use for a while, you will be
fasinated with the discoveries you will make.


John R. Spencer , (303) 229-3271)

Finally an explanation of these signals, which I first noticed maybe 3 decades ago when I happened to hook a piece of wire to the input of my old HP spectrum analyzer at home. Found the sweeping signals mentioned here, running from around 6 MHz up to around 15 MHz, where they weakened and faded out during the daytime. Some swept at 25kHz/sec, some at 50, and some at 100. They went straight through all frequencies, including HF aircraft bands around 8.8 MHz. Some time later, I noticed they started dropping out as they approached these critical frequencies, and picking up again once past them. Strong signals, as they were easily visible on 10 feet of wire across the room directly into my old SA, which has only mediocre sensitivity. (Though it does shoe the Australia broadcasting signal at 9580 kHz as 50 uV with the same short piece of wire in the early AM here in New York, USA.)