>From ARRL Letter Vol 18, No. 44
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"BUZZ SAWS" ABOUND ON HF
"The HF buzz saw is dead; long live the HF buzz saw!" That might be the cry
from the crowd these days as various buzzing intruders have been showing up
with some regularity on HF. Sometimes, though, it's hard to distinguish one
intruder from the other on the basis of anecdotal reports from amateurs.
Recent reports of the so-called 125-Hz "buzz saw" intruder on the 80-meter
band are a case in point. The intruder--heard primarily in the US
northeast--had plagued amateurs as well as an aeronautical weather station
just below 80. In the wake of protests from amateurs and coordination
between the ARRL and Radio Amateurs of Canada, the transmissions--determined
to come from two HF surface wave radar facilities in Newfoundland--moved off
the amateur band. The signal has not been heard on 80 meters since early
October.
IARU Region 2 Monitoring System Coordinator Martin Potter, VE3OAT, credited
ARRL and RAC assistance in getting the HFSWR systems moved off the amateur
bands. The HF surface wave radar sites in Newfoundland are a joint project
of Canada's Department of National Defence and Canadian industry. Canadian
officials see the technology as playing a role in maintaining Canada's
territorial sovereignty as well as for search-and-rescue operations and to
assist in combating illegal immigration and drug smuggling.
Responding to the initial "buzz saw" reports, amateurs in the US and
elsewhere alerted the ARRL Monitoring System to a plethora of signals they
claimed were the now-infamous intruder. It's now clear, however, that a
similar mystery visitor on 40 meters is not coming from the Newfoundland
HFSWR facilities. "Although a number of additional reports of buzz-like
interference were received from the western USA and elsewhere, none could be
confirmed as due to the same signal," Potter said. The signal has been
widely reported in Region 1.
ARRL member Dave Bowker, K1FK, in extreme northern Maine was the first to
report--and graph--both the "original" 80-meter buzz saw as well as the
more-recent 40-meter signal. "Although it sounds similar, it has three
distinctly different characteristics," he said. The signal's sidebands
extend 7 kHz either side and "it is a frequency hopper, moving randomly in
time and frequency steps."
Steve Yates, AA5TB, in Fort Worth, Texas, also has monitored, graphed and
recorded the 40-meter signal, and his observations are consistent with
Bowker's. "The transmissions would jump frequencies every few minutes but
not at regular intervals," he says. He reports measuring the different
transmission center frequencies at about 7020, 7040, 7050, 7070, 7080 and
7090 kHz, and believes the signals came from the same transmitter. Yates has
posted information about this and other intruders at
http://home.swbell.net/aa5tb/.
The IARU Region 2 Monitoring System now refers to the 40-meter intruder as
an "unusual jammer," but concedes, "If the signal is truly a jammer, it is
not clear who or what the target is." Potter says the signal is modulated by
strong harmonics of 50 Hz and 100 Hz and seems to be associated with a
"wobble" or "bubble" jammer on the same frequencies.
Another "buzzer" on 3795 kHz has been reported to the ARRL Monitoring System
from hams in various parts of the US including Rich Chatelain, K7ZV, in
California, and Bill Avery, K6GNX, in Nevada. Both agree that the signal
appears to be coming from somewhere along the Utah-Nevada border. "It
transmits for 80 seconds every five minutes. It is approximately 20 kHz
wide," Avery said.
Potter says the 3795 kHz signal is worthy of further investigation.
Additional reports and observations are welcome to ARRL Monitoring System
Administrator Tom Hogerty, KC1J, thogerty@arrl.org.
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73, Guy
k2av@contesting.com
Apex, NC, USA
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