roswell

A review of this systEm by members of the University staff
has b4}ell published in "Transactions of the American Geophysical
Union{2}11 Earlier work on this development has been reported
by members of this Research Division in"Technical Report 93·(or(3)
and in the "Jo11rnal of the American Meteorological Society" 4).
A manual for those interested in making use of balloon syste.s
of this type has also been published as "Section II, Operations"
of our "l'eclmical Report 93.02 11 (1). This report consists of a
disc,1ssion o.f instrumentation for balloon systems, techniques
for launching and tradtng, and telemetering from balloons as
developed and tested at New York University.
c. Telemetering From Balloon Systems
The second requirement of this project was the_investigation,
development, and testing of balloon borne telemetering systems. ( )
The development was completed in June of 1948 and a final report 7
of work accomplisred and recommendations made to the sponsor at
that time.
Two types of transmitter ,nits were suggested as a means of
accomplishing ~he telemetering of data from a balloon to ground
station receivers. A high freq,1ency syatea, making use of line-or-
sight transmission allows for accurate positioning of the balloon
system from two' ground stat~.ons. The line-of-sight characteristic,
however, limits the range of this type transmitter, and ranges
in excess of 250 miles are not to be expected with a balloon
system floating at 40,000 ft.
Three line of sight transmitters were designed for use in
balloon work. The first, the FM-1, was designed to operate at
72 me, using a conventional reactance tube modulator. Several
stages were included to deliver 1 watt o~tput at tbe design
frequency. The unit was cruitP. complicated and the required
input :oower large due to the requirement for several stages
to transmit at the high frequency. Fig. 4 is a schematic of
the FM-1 transmitter.
In order to overcome this limitation of FM sets, a two tube
transmitter was developed (Fig. 5). Variation in vacuum tube
resistance is used to modulate the oscillator plate voltage of
a self•excited oscillator in accordance with the audio signal.
This provides the freq,.1ency modulation desired. In order to
mainta~n a stable center frequency and render the oscillator
insensitive to changes in snpply voltage, a neon tube voltage
re~1lator was included.