(2) Sun. The upper operating tempera-
ture limit--of + 125°F applies to the
If transmitter's antenna touches any
TEMPERATURE OF THE COMPONENT, not
part of the helicopter during transmis-
the temperature of the air around it. For exam-
sion, the transmitter's range will be
ple, with the thermometer reading + 85°F in
the shade (the air temperature), an item sitting
in the direct sun could easily exceed the + 125°F
limit. The M122 components must therefore be
protected from the direct sun. When doing this,
always use a nonmetal covering and allow venti-
(2) The operating range is decreased
bad weather conditions and instructions such
lation as an unventilated box placed over a
as hilly terrain in the signal path.
receiver in the sun will allow the device to get
increased by having a clear line of sig ht path.
almost as hot as if it were in the direct sun. A
Therefore, the operator should place the
few air holes in the sides of the same box could
receiver in a clear area, if possible, and choose a
make a 20 or 30 degree difference. The same
suitable location and altitude for the helicopter
which will provide a clear line of sight from
temperatures over + 160°F have been meas-
transmitter to receiver.
ured in unventilated metal sheds and box cars
during hot summer days.
(3) The M122 is primarily designed to
function from land-based stations. However,
(3) Storage in the field. Do not store
the capability for helicopter usage (based on lim-
the M122 components with the batteries
ited tests) was successfully demonstrated in the
installed even for a day when the temperature
tropics. It has limited application in Arctic use.
is over 80°F during the day. If a refrigerator is
No data are available for desert application. It
available, store the batteries in it during hot
is recommended that the M122 be set up for a
weather (or all the time, if possible). Cold stor-
trial operation to simulate actual operating con-
age greatly extends the shelf life of batteries
ditions prior to the actual mission.
and high temperature storage shortens it (espe-
cially if the battery leaks). See shipping and
f. Dual Priming Method.
storage, chapter 4, or more details.
(1) An "in-effect" dual priming of
d. Blowing Dust and Sand. Blowing dust
charges can be done with the M 122 receiver by
and sand can cause damage to the external mov-
wiring two M6 blasting caps in parallel instead
ing arts of the M122 components.
of the usual series connection.
switches, push buttons, transmitter antenna,
and binding posts should be given protection
during transport and use in such environments.
After use under these conditions, clean the
items thoroughly (see chapter 3 for mainte-
Use of the parallel "dual-priming is not
advised when the ambient temperature
e. From Helicopter.
is closer than 10°F to either the high or
the low operating temperature limit.
(1) When o crating the transmitter
from a helicopter, follow the normal procedure
for checkout and code selection. To fire the
transmitter, place it on the floor of the helicop-
ter in a vertical position and fully extend the
(2) The dual priming method may be
antenna. With the door opened, the operator
used providing the connection is limited to two
blasting caps wired in parallel, extension wires
should face the receiver site so he has a clear
that do not exceed 100 feet each, and two No.
line of sight. Hold the transmitter and depress
18 conductor cables. The blasting caps are to
the fire button. The transmitter's antenna
be used strictly for dual priming of one charge.
must not touch any part of the helicopter dur-
(3) Refer to FM 5-250 and TM 9-1375-
213-12 for proper preparation of explosive
charges and priming.