Avionics News - September 2023 - 45

unit, BC-608-A. Areo Antique and other internet sites
provided more information. This unit was part of the
system that preceded IFF, or Identification Friend or
Foe, which is the military equivalent of ATCRBS (and
Mode-S) transponders. My own example was staring me
in the face!
At the start of World War II, radar was
in its infancy. The British
developed a radar system
known as Chain Home,
which lasted until 1942.
The Chain Home system
(nor any radar) could not
identify the difference
between friendly targets
and enemy targets.
To make up for this
deficiency, the Allies
developed a system
known as the Pipsqueak
radio identification
system.
The Pipsqueak system
(pictured) worked with the
aircraft communication
radio. For 14 seconds,
the Pipsqueak system would
send a carrier wave through the communication
transmitter. Multiple stations on the ground would
receive the signal and use direction finding techniques to
determine the position of the transmitting aircraft.
Presumably, 14 seconds was not enough time for
Axis powers to detect the signal and locate it. Assigning
the frequency and transmitter starting time would give
the system a modicum of stealth. Still, if the system
transmitted repeatedly for 14 seconds of every minute,
one could find it conceivable the Axis powers would
locate the aircraft, eventually.
One disadvantage of the system is during the 14-second
transmission period the communication radio was not
available for normal voice communication. The control unit
has a contactor switch, which will disable transmissions
when set to the OUT position. Transmissions could also
be prevented by stopping the clock, but allowing the clock
to run continuously would eliminate the need
for the pilot to worry about
resynchronizing the time.
The final control, WIND,
has an obvious function
once you know the indicator
on the unit is a second hand.
Once wound, the clock
could run for as long
as 24 hours, although
standard practice was to
wind it every 12 hours.
Of note are the markings
on the contactor, and some
internet sources indicate
a 14-second transmit
period. A copy of the official
documentation said the
transmit period is 15 seconds.
In addition to the
instrument pictured here,
the complete system included a relay box, and
of course, the transmitter and radio control box. The
contactor came equipped with a heater coil to prevent
the mechanical clock from freezing at high altitude
where temperatures were low. As an indication of how
secret this system was, the radio control box included a
detonator, which would destroy the box automatically
if the airplane crashed, or manually, if the airplane was
forced to land.
avionics news * september 2023 45
Continued on following page

Avionics News - September 2023

Table of Contents for the Digital Edition of Avionics News - September 2023

Contents
Avionics News - September 2023 - Intro
Avionics News - September 2023 - Cover1
Avionics News - September 2023 - Cover2
Avionics News - September 2023 - 1
Avionics News - September 2023 - Contents
Avionics News - September 2023 - 3
Avionics News - September 2023 - 4
Avionics News - September 2023 - 5
Avionics News - September 2023 - 6
Avionics News - September 2023 - 7
Avionics News - September 2023 - 8
Avionics News - September 2023 - 9
Avionics News - September 2023 - 10
Avionics News - September 2023 - 11
Avionics News - September 2023 - 12
Avionics News - September 2023 - 13
Avionics News - September 2023 - 14
Avionics News - September 2023 - 15
Avionics News - September 2023 - 16
Avionics News - September 2023 - 17
Avionics News - September 2023 - 18
Avionics News - September 2023 - 19
Avionics News - September 2023 - 20
Avionics News - September 2023 - 21
Avionics News - September 2023 - 22
Avionics News - September 2023 - 23
Avionics News - September 2023 - 24
Avionics News - September 2023 - 25
Avionics News - September 2023 - 26
Avionics News - September 2023 - 27
Avionics News - September 2023 - 28
Avionics News - September 2023 - 29
Avionics News - September 2023 - 30
Avionics News - September 2023 - 31
Avionics News - September 2023 - 32
Avionics News - September 2023 - 33
Avionics News - September 2023 - 34
Avionics News - September 2023 - 35
Avionics News - September 2023 - 36
Avionics News - September 2023 - 37
Avionics News - September 2023 - 38
Avionics News - September 2023 - 39
Avionics News - September 2023 - 40
Avionics News - September 2023 - 41
Avionics News - September 2023 - 42
Avionics News - September 2023 - 43
Avionics News - September 2023 - 44
Avionics News - September 2023 - 45
Avionics News - September 2023 - 46
Avionics News - September 2023 - 47
Avionics News - September 2023 - 48
Avionics News - September 2023 - 49
Avionics News - September 2023 - 50
Avionics News - September 2023 - 51
Avionics News - September 2023 - 52
Avionics News - September 2023 - 53
Avionics News - September 2023 - 54
Avionics News - September 2023 - 55
Avionics News - September 2023 - 56
Avionics News - September 2023 - 57
Avionics News - September 2023 - 58
Avionics News - September 2023 - 59
Avionics News - September 2023 - 60
Avionics News - September 2023 - 61
Avionics News - September 2023 - 62
Avionics News - September 2023 - 63
Avionics News - September 2023 - 64
Avionics News - September 2023 - Cover3
Avionics News - September 2023 - Cover4
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