"Intruder Signal" on 40 Meters Remains a Mystery for Now
A September 9 spectrogram of the 40-meter "intruder" signal from VE6JY.
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NEWINGTON, CT, Sep 9, 2004--An unidentified signal that's been showing up on the 40-meter phone band on or about 7238 kHz has mystified amateurs in the western US and Canada, where it's been heard frequently for the past few weeks. Although it resembles a steady carrier, a closer inspection suggests that the intruding signal actually is a series of closely space signals. Don Moman, VE6JY, in Edmonton, Alberta, says he's been hearing the signal quite loud at his QTH.
"This signal looks a lot more interesting than it would sound--just a broad tone/hum/buzz, depending on where you tune," he said. One spectrogram from VE6JY showed perhaps a half-dozen or more discrete signals. "It's certainly loud enough out here, peaking broadly south-southwest from Edmonton," he said. Moman was using a 5-element Yagi and was hearing the signal at 10 dB over S9.
That conforms with observations reported by Bob Gonsett, W6VR, at Communications General Corp (CGC). He says engineers at the CGC lab in Fallbrook, California took a quick look at the intruder September 6 at around 2120 UTC and found "several close-spaced CW carriers--perhaps from one specially modulated transmitter, perhaps from transmitters at different locations," he reported. CGC reported the signals appeared on 7238.063, 7238.150, 7238.237 and 7238.412 kHz, with the 7238.237 kHz signal being "the strongest of the group."
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CLICK HERE to hear an audio clip of the "mystery" signal in the vicinity of 7238 kHz as heard at the QTH of VE6JY in Alberta. [MP3, 00:20]
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While no one's sure what it is, the FCC HF Direction Finding Facility has been able to determine that it's coming from somewhere north of Prescott, Arizona, and west of Interstate 17. FCC monitoring indicates the "buzz" is centered on 7238.1 kHz with a bandwidth of about 1 kHz and spikes spaced at about 90 Hz apart.
Reports to the International Amateur Radio Union Region 2 Monitoring System indicate the signal has been heard from about 1700 to 2130 UTC, although Moman reported hearing it at around 0300 UTC and said the signal even went off the air for a few seconds while he was listening to it. Jack Roland, KE0VH, in Colorado also heard the signals for a couple of evenings this week. "Something is not right there," he remarked.
High Noon Net Manager Bill Savage, N5FLD, in Albuquerque, New Mexico said several net participants--in Nebraska, Colorado, Nebraska, Wyoming, Minnesota and Arizona--were able to hear the mystery signal.
If you
have any additional information on this or other unidentified signals in the
amateur bands, send reports by e-mail to Chuck Skolaut, K0BOG, cskolaut@arrl.org.
Page last modified: 02:24 PM, 14 Sep 2004 ET
Page author: awextra@arrl.org
Copyright © 2004, American Radio Relay League, Inc. All Rights Reserved.
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