No
6
Subjects:
FCC:
Exam
Locations
VOR:
What is a VOT?
GPS:
Rollover
Error
Navcom:
Obsolete
MK12B
FCC
Exam
Locations
Q.
"Where can I take my FCC exam for the General
Radiotelephone Operators License?"
A.
The exam is now given at many points in
the U.S. and worldwide by examination managing
organizations (not the FCC). Fees
range from about $35 to $75. If the exam is
successfully taken, you are issued a Proof of
Passing. This is submitted to the FCC which
issues the license. To find locations and exam
schedules, you may telephone the
following organizations. They arrange
for examinations in most states.
Electronic Technicians Assoc. International
- 317/ 653-4301
International Society of Certified
Electronics Technicians - 817/ 921-9101
National Assoc. of Business and Educational
Radio - 1-800/ 759-0300
National Assoc. of Radio Telecommunications
Engineers - 508/ 533-8333.
W5YI Group - 817/ 461-6443
VOR
Q. "What is a VOT?"
A
A VOT is a VOR Test
Facility. A transmitting station
located at selected airports, the VOT enables a
pilot to check the accuracy of a VOR receiver
while on the ground and from almost any position
on the airport. After tuning the test signal, and
turning your omni-bearing selector, you will note
that the bearings you see have nothing to do
with your position with relation to the
station. The reason is, a VOT emits only two
bearings, not 360 radials, as in the case of
regular VOR station. Those test radials---0
degrees From and 180 degrees To---provide the
reference you need for checking.
The procedure is this: Tune in the VOT
frequency (shown in an airport facility directory
(or on a sign on the station itself). Turn your
OBS (omni-bearing selector) until the needle
(or CDI, Course Deviation Indicator) centers, at
approximately 180 degrees. The To-From flag must
indicate "To". WIth the needle centered,
note the difference between 180 and the bearing
shown on your display. That difference is your VOR
error.
Next, rotate the OBS until the needle
centers, near 0 degrees. The To-From flag must now
indicate From. The difference between 0
degrees and the bearing shown on your display is
the error.
If your airplane is equipped with an
RMI (Radio-Magnetic Indicator, which displays VOR
information) it will indicate 180 degrees on any
setting of the OBS.
As in regular VOR stations, the VOT
has identifiers; some emit a series of dots,
others a continuous tone.
It is permissible to use a VOT while
in flight, but subject to certain areas and
altitudes. This information may be obtained
from a Flight Service Station.
GPS
Rollover Error
Q. I hear that my GPS may malfunction at
the end of August (1999) because of changes to the
satellites. What should I do?
A.
Some GPS receivers may be affected when
the US Air Force uploads data to the
satellites and resets the week number (from 1024
to 0) on August 22, 1999. There is a possibility
that some GPS receivers may provide incorrect
navigation or fail to lock on properly. In
many instances, this will be a temporary condition
and resolve itself in a few weeks. You might help
the process by using the "autolocate"
function each time the GPS is turned on for the
first few weeks after August 22, 1999.
You may, however, obtain more
detailed information on the websites of the GPS
manufacturers. Many of their web addresses
can be found at the following URL: www.navcen.uscg.mil/gps/default.htm.
A visit to your manufacturer's site will often
provide specific rollover information
on your unit.
Navcom
Obsolete MK 12B
Q.
I have a 1962 Cessna 172 with a
Mark 12B navcom. The VOR doesn't work at
all. On the com side, it sends and receives
on 122.95, but on other channels it only
receives. Is it worth repairing?
A.
Airplanes may go on forever, but radios
won't. This may hurt your feelings but 18
years ago, when I began to repair radios, if a
Mark 12B came into the shop, all the technicians
simply laughed.
This isn't to say that age alone
should condemn a radio. But a lot has
happened since the Mark 12B . Most
important, frequency tolerances have been
tightened to allow more than 600 additional
channels into the band. This radio doesn't meet
the new standards.
Your radio also has the
electronic dinosaur known as the
"vacuum tube," Last we heard, some
outfit in the (former) Czechoslovakia made some
replacements at high prices. With their hot
filaments, tubes can be expected to burn out like
an ordinary electric light bulb.
. The Mark 12B also has complex
and troublesome switch assemblies that get dirty
or lose tension. Even if you fix this antique, you
still end up with a 30-year-old radio
that will soon need repair again---with many
components no longer available.
