Interference to Air Traffic Control
is a Spectrum Management Officer
with the Spectrum Management Program. He works in the Vancouver
Island District Office in Victoria, BC.
As a Spectrum Management Officer, my primary duties focus on the
orderly management of the radio frequency spectrum, which includes
all manner of radio waves, from about 3 kHz to 300 Ghz. Spectrum
management accomplishes this by issuing authorities (such as radio
station licenses) and maintaining and ensuring its continued health
through the enforcement of the Radiocommunication Act, and
associated regulations, policies and standards. Part of my job
involves the issuance of these authorities and the resolution of
interference problems that can jeopardize the use of these
authorities. Spectrum Management Officers work to make sure that the
radio frequency spectrum is operating smoothly.
The following case story illustrates one small but vital facet of
the work a Spectrum Management Officer may be called upon to
perform, the suppression of Harmful Radiocommunication Interference:
It’s January 2, 2004 – I receive a call from the Air Traffic
“Area Control Centre” (ACC) at Vancouver International Airport. They
advise me that pilots along high altitude flight paths within the
Vancouver ACC zone are reporting hearing superfluous chatter on the
prescribed radio channel. At times, the aircraft are unable to hear
Air Traffic Control directions over the interference. This
represents a safety hazard, as communications between Air Traffic
Control and aircraft are being compromised. The Air Traffic Control
stations on the ground can’t hear the interference. The signal is
too weak. They’ve called us to enlist our help in resolving this
aeronautical interference problem.
Initial information provided by Air Traffic Control states that
aircraft flying at elevations of 30 000 feet have reported hearing
interference on the ACC radio channel while flying over Vancouver
Island, from south of Victoria to north of Campbell River – a
distance of approximately 300 kilometers! I request that Air Traffic
Control try and get as many details as they can from the pilots
experiencing the interference, such as names of people, places,
radio call signs, etc., and the times they were heard. This type of
information can be vital to resolving a problem of this nature. They
say they will try. Given the large area, and few details, there is
not much information to go on.
February 2, 2004 – Air Traffic Control has tried to gather as
much information as they can with respect to times, names, or places
that pilots may have picked up. The information they’ve gathered,
however, is limited. We’ve just caught part of a radio station call
sign: VE7. That is the prefix assigned to Amateur Radio stations
operating in BC.
Now we have a lead.
Little by little we pick up tidbits of conversations heard by the
high-flying aircraft: “Jack and his wife Linda ...” “Wayne and Jerri
have paid off their mortgage...” and other such statements. There is
nothing definitive, but the information provided by Air Traffic
Control may help us identify the source.
I’m now using a remote monitoring station that our office has set up
in Nanaimo, BC, to record voice traffic heard on the ACC channel in
question. I am hoping our Remote Automated Monitoring System (RAMS)
might be able to capture some of the interference heard by the
It’s February 18th – I get the break I was looking for. RAMS
has recorded a brief conversation between two amateur radio
operators. They used their call signs and referenced a location in
Nanaimo! Unfortunately, I am still unable to pinpoint the source, as
the call signs I recorded are not very clear. The amateur radio
operators I contact claim they were not on the air at the time I
recorded the interference. The call signs recorded is too garbled to
be clearly heard. I’m going to need some help on this problem.
I contact one of our local radio suppliers who is actively involved
with the Amateur radio community and ask if he can make some
discrete inquiries within the amateur community. He agrees, and I
provide him with the bits and pieces of conversation we’ve
It’s now almost the end of the day and I receive another offer of
assistance from the BC Amateur Radio Coordination Council ( BCARCC
), who coordinate repeater operations among amateur groups.
I guess word travels fast within the amateur community, because I
hear back from BCARCC, and they claim that the interference is
likely coming from a station operated by the Nanaimo amateur radio
club. Someone there knows someone who has paid off their mortgage.
I speak to some of their members, and with the information I’ve
recorded with RAMS, we confirm the identity of the radio station
operators, and the amateur radio repeater station they’re using.
The club agrees to turn off their repeater until we can determine
what is causing the radio station to radiate a spurious signal
falling onto the Aeronautical Communications band. They are being
very cooperative and immediately shut down the offending station.
They are also working with us to identify the mechanism responsible
for causing the problem.
Monday, February 23rd – I receive an email from the a club
member that says they have identified a faulty Duplexer, and that it
will be replaced. (A duplexer is a passive device that allows a
transmitter and a receiver to share the same antenna.) The Nanaimo
club has agreed to keep the station off the air until I can attend,
to ensure the problem has, indeed, been dealt with.
Tuesday, Feb. 24th – I am overseeing the replacement of the
problem device, and test the output of the repeater to ensure that
the interference problem has been successfully resolved.
Once I am satisfied that everything
is operating as it should, I advise Air Traffic Control and our
Management team in Victoria that the interference has been
This case, albeit a bit out of the ordinary, offers a snapshot of
one of the many duties that the Spectrum Management Officers of
Industry Canada perform each and every day across Canada. With the
use of technology, skill, determination, diligence and, most
importantly, cooperation, the Spectrum Management Program works to
ensure that Canadians enjoy the many services and benefits that are
provided through the use of our airwaves.