Model rocket manufacturer Estes Industries sold a radio-based
locating device called Transroc that fit inside the main body
of a model rocket or model airplane.
Section B. Modes of Operation
The TRANSROC has three basic modes of operation one of which,
TM (telemetering), can be further broken down and expanded into
several subdivisions. This versatility offers the ESTES rocketeer
many hours of educational enjoyment and a wide field of new
horizons in model rocketry.
B.1 Rocket-Finder Mode
The most basic mode of operation for the TRANSROC is as a rocket finder.
The basic kit is supplied complete with all components needed for operatiom
in this mode. The only accessory needed for rocket finding is a good
In the rocket-finder mode, the transmitter is pulsed on approximately once
per second for approximately one-fifth second and is off during the remainder
of the cycle. This provides a beacon signal similar to the ones used in
space capsules and survival equipment for locating astronauts and fliers after
they lower by parachute into the ocean. This "cw" (continuous wave)
type signal provides excellent penetration in the presence of severe
interference. The rocket-finder signal from the TRANSROC mixes with any other
signals which are being received to produce an easily distinguishable audio
beat note in the receiver's speaker.
Depending upon the level of interference present and the sensitivity of the
receiver used, it is possible to receive the TRANSROC in the rocket-finder
mode at distances of up to five miles or more during flight and up to a few
hundred yards after the rocket has landed. Field tests have shown battery
life up to 24 hours or more.
The telemetering modes are similar to the rocket-finding mode in that the
transmitter is turned on and off in sequence to convey information. The
cycle is much shorter for TM, however. The time during which the transmitter
is off during each cycle is controller by the appropriate transducer such as
a photocell, thermistor, etc.
Current consumption is only one-third greater in the telemetering modes than
for rocket finding, but useful battery life is shortened more than this. The
shorter usable battery life is mostly due to the fact that a much stronger
signal is needed for receiving good TM than is needed for rocket finding.
B.3 Microphone Transmitter
The microphone transmitter mode is significantly different than the rocket-finder
or telemetering modes in that insteawd of the transmitter output being turned on
and off intermittently, its amplitude (strength) is varied in proportion to the
sound striking the microphone. It thus transmits in the same manner as an AM
(amplitude modulated) radio station or walkie-talkie. This signal can be tape
recorded as it comes from the receiver. The tape recording thus obtained will
include your voice during countdown, engine burning noises, and a variety of
sounds caused by the wind rushing by, the ejection charge, and the rubbing
between the rocket body and the parachute shroud lines, etc., after ejection.
Battery life is shortest in the microphone mode due to higher current drain and
a higher minimum usable battery voltage. A new battery is adequate for six to ten
flights if recovered and turned off after a few minutes each time. THe battery
can then be used for several TM flights followed by several rocket-finder flights.