A 2-12 MHz demonstrator was built with acceptable dimensions for land
mobile applications (height=90cm, length=2.4m, width=30cm). All
adjacent bandwidths were covered within the 2.5:1 VSWR specification.
Its efficiency was measured every 0.5 MHz on a test station by substitution
of a refence whip. These values were not more different than ñ1dB
from the values deducted from the Q-factor measurements.
A second version with a 2-30MHz frequency range was developped. It was
qualified for military environment with mechanical tests (chocks,
vibrations) and climatic tests (-40C +70C, rainfall, salted
fog, windspeed, ice, dusts, etc...) according to MIL SPEC standards.
It is now in service in quantities in the French Army.
III FIELD TRIALS
Extract from the field trial made by Thomson-CSF in octobre 1994 for
the French Army:
"From 0 to 600 km, all Q/S and S+N/N measurements have confirmed
a behaviour without fault of the half-loop. It always gave
results much higher than that of the guyed 5m whip whatever the
climatic conditions were (rain, intensive fog...). We tried to
use the station in the most extreme environment conditions noting
the link results, while driving under the rain, under the high
voltage cables either parallel or perpendicular to the road, measuring
signal/noise in highly industrialized towns (like Clermont Ferrand)
, on the country roads through humid forests, etc...
"The results were independant of these environmental conditions,
the reception signal/noise beeing only slightly affected under
the very high voltage cables.
"...The half-loop antenna bring the best
results in terms of link budget and listening comfort".
Thomson-CSF also confirmed that the half-loop antenna on a moving car
allows fast data transmissions without fault in the silent zone
of the whip antenna, and that it improves the probability of successfull
synchronisation of the new procedures in bad ionospheric conditions.
Other field trials were successfully conducted in France and several
foreign countries in the Middle East and America.
IV RADIO INTERFACES
Mobile and naval half-loop antennas and fixed/semi-fixed loop antennas
using the same electronic components and softwares are working
today with various radiosets for military and civilian applications
as well, in frequency hopping, ALE or fixed frequency modes A
modular and universal interfacing unit makes it possible to fit
the antenna at the radioset RF output using the control interfacing
designed for its antenna coupler.
The control exchanges can be done in RS232 or multiwire cable according
to the speed. The frequencies can be provided in clear, as a channel
number or not provided at all. A frequency counter is necessary
in this last configuration.
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STAREC has been involved for a
long time in the design of specialized antennas, a wide range.of
which has been proved in operation with French and foreign Armed
This equipment is mainly used in fixed or mobile weapons or telecommunication
systems, such as shelters, trucks, battle tanks, forward armoured
vehicles, etc. STAREC is involved in the RITA, ROLAND, PR4 G,
HF Carthage programs.
half loop on vehicle