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Intruder signal on 40 metres
remains a mystery for now
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 spaced signals.
Don Moman, VE6JY, in Edmonton, Alberta, says the signal is 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."
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.
Source: ARRL Letter - courtesy of The
American Radio Relay League
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