TM 5-6675-318-14
( 1 ) A n t e n n a / P r e a m p l i f i e r l o c a t i o n . A A n t e n n a l o c a t i o n w i l l d e p e n d o n s i g n al
r e c e p t i o n f a c t o r s ,
interfering signals, and survey requirements.
The point for
which a position is actually computed is the electrical Conter of the antenna which
is indicited by a red band.
N o r m a l l y , t h e a n t e n n a i s p o s i t i o n e d d i r e c t l y o v e r t h e
point to be determined,
such as a previously established benchmark. If the antenna
c a n n o t b e l o c a t e d d i r e c t l y o v e r t h e f i x e d p o i n t d u e t o p h y s i c a l c o n s t r a i n t s , p o or
s i g n a l r e c e p t i o n , o r i n t e r f e r i n g s i g n a l s , a n d a m o r e a d v a n t a g e o u s l o c a t i o n i s a
s h o r t d i s t a n c e a w a y , r e f e r e n c e t h e r e d b a n d o f t h e a n t e n n a t o t h e f i x e d p o i n t.
( 2 ) S i g n a l r e c e p t i o n .
T h e s a t e l l i t e s i g n a l p r o p a g a t e s i n d i r e c t l i n e o f
sight. The signal could be absorbed,
r e f l e c t e d ; o r r e f r a c t e d i f t h e r e a r e l a r ge
objects between it and the antenna/preamplifier assembly. For this reason, the
antenna/preamplifier assembly should be located where it has an unobstructed view of
the horizon above 10 degrees of elevation.
The red band must be located a minimum
of 4 meters (13 feet) from large vertical structures and 1 meter (3.25 feet) above
l a r g e h o r i z o n t a l s t r u c t u r e s .
Close proximity to such structures could cause the
receiver to receive two signals whose phase relationship will change during
r e c e p t i o n .
To minimize signal multipath, avoid close proximity to smooth bodies of
water.
Do not locate the antenna/preamplifier closer than 10 meters to antennas of
the same wavelength (such as TV antennas).
( 3 ) I n t e r f e r i n g s i g n a l s .
The antenna/preamplifier assembly should be
located in an area of minimum radio interference. Areas which have radio
transmissions in the 150 and 400 MHz ranges must be avoided. Medium frequency radar
and high power communication antennas should be avoided because they may emit
enough RF energy to damage the equipment.
If it is necessary to operate near such
equipment, the antenna must be shielded and moved until proper operation is
obtained .
High voltage power lines, high voltage transformers, or excessive noise
from car ignition systems should be avoided.
( 4 ) R e c e i v e r / P r o c e s s o r l o c a t i o n.
NOTE
In most instances, the horizontal offset distance between the antenna
and the survey point should not exceed 30 m (98 ft).
I f p o s s i b l e , l o c a t e t h e r e c e i v e r / p r o c e s s o r o u t o f d i r e c t s u n l i g h t , or
provide some form of shade.
The receiver/processor must be located within 30 meters (98 feet) of the antenna/
preaplifier unless extra antenna cable lengths have been obtained. A maximum cable
length of approximately 60 meters (196.8 feet) can be tolerated. The location of
the receiver/processor must be free from vibration. Therefore, certain mobile land
installations will require the receiver/processor to be shock-mounted.
n. Prepare a station description card, DA form 1559 of the antenna location in
accordance with TM 5-441.
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