mass-production methods and quality eontrol associated with stan-
dard dry batteries gave greater assurance of satisfactory IS rformance.
Subsequent measurements made of the temperature inside the trans-
mitter battery pack showed that the temperature can be maintained
above -1ooc if the transmitter and batteries are housed in a box
insulated with one-to two-inch walls of Styrofoam. This insulation
is effective even through long nighttime periods when no solar
heating is added.
One type of battery tested in flight was a light-weight wet cell
(Burgess Type AM) of the "dunk" type, (magnesium • silver chloride).
These cells were vacuum-packed to provide indefinite shelf-lite.
Activated by immersion in ~~ter just before release, they were ex-
pected to produce a constant voltage over a period of 6 hours to
overcome cold temperature effects. Those units used proved to be
rather unsatisfactory and subject to erratic behavior. Further-
more the cost of the cells was very great compared with ordinary
cells.
E. Radio Direction-Finding
For ground stations, when the balloon-borne transmitter is a T-69,
.the SCR-658 RDF set has been used. With such a set the radio sig-
nal can be picked up at distances up to 150 miles and good azimuth
bearing may be obtained (accurate to less than one degree). Although
the elevation angle may be obtained with equal accuracy when free
from distortion, angles of less than 13 degrees are usually affected
by ground reflection to such an extent as to render them valueless.
To extend the range over which such sets were effective, two or more
usually were used, positioned along the expected track of the balloon
at intervals of about 100 miles. With two sets giving crossed azi-
muth "fixes" the position m~y be d~termined. If the elevation
ar1gle is above 13 degrees, it is possible to fix the belloon with one
SCR-658 (assuming the pressure altitude is kr.own).
For details of the mainte~~nce and use of the SCR-658, see War De-
partment publication T.M. ll-1158A.
VVhen aircraft are used to follow and position the balloon, the use
of a radio-compass is found ~o be feasible, using the AX-1 tre.ns-
mitter at a frequency that is within the limits of the compass re-
ceiver. By homing on the signal end flying along the indicated
bearing until the compass needle reverses~ the balloon~ position
may be found from initial distances or up to 500 miles. No appre-
ciable cone of silence has been observed in recent flights which
used a transmitter operating at 1746 kc.
Radio compass equipmen~AN/A~-~ is described in U.s. A. A. F.
publication T. o. 68-10.
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