Technical Manual

54 D C U M a i n t e n a n c e a n d O p e r a t i o n M a n u a l
DCU Antenna Pattern Test
Field Data
1. Connect an RF power meter (input) to a calibrated signal generator (output).
2. Transmit 460 MHz energy from your signal generator into your power
meter and confirm that the power received agrees with the power
transmitted.
3. Remove your calibrated signal generator from the power meter and connect
it instead to the coax and antenna (in place of the DCU).
4. Configure your handheld spectrum analyzer to capture signal strength
measurements and record time, date, latitude, and longitude. Ensure that the
spectrum analyzer has a GPS lock.
5. Turn on the signal generator and have it transmit a 2.00 W CW signal just as
in Step 2.
6. Perform a small circular walkabout around the antenna. Collect periodic
data points that start and end at the same location, and maintain a consistent
distance from the antenna under test.
1 A rope may be used to measure a consistent distance from the
antenna. 3m and/or 10m lengths are useful.
2 Collect extra samples (perhaps in 1 foot increments) in areas of
interest where the power level appears to change.
3 Be aware of your surroundings when conducting this test.
7. If a particular area of terrain has been reported as being problematic, the test
may be continued to investigate that area. While the signal generator
continues to transmit a carrier wave, travel to the test area. AclaraONE
should be used to take other nearby DCUs temporarily offline. Use the
handheld spectrum analyzer to take numerous data points (including time
and location.) Samples should be taken in areas that are known to perform
well in addition to the area under study. You could collect samples while
approaching the test site, samples upon arrival, and samples when leaving.
N
OTE If the DCU transmit frequency is occupied for a long period of time, it could
cause queued commands to be rejected by the DCU(s). Depending on the
nature of the issue being investigated, it may be preferable to use another
licensed frequency (other than the DCU Tx frequency) so that the entire
system is not tied up for the duration of the test.
1 Certain battery operated MTU devices may also expend more
battery life as they determine if a transmission pertains to them or
not.
2 Before leaving the affected area, the spectrum analyzer should be
temporarily placed in waterfall mode to test for interferers from
nearby channels.
8. Upon completion of the test, return to the DCU. Cease CW transmission.
Remove the signal generator. Reconnect the coaxial cable(s) to the DCU.