(or airborne) Interception. Special electronic interception
equipment mounted in an aeroplane. Space inside an aeroplane
dictated that much shorter wavelengths than those used
ground-based equipment had to be developed. Centimetric
proved to be the defining breakthrough.
to surface vessl radar. This was a system particularly
detecting 'U'-boats. New and novel scanning aerials were
Auxiliary Territorial Service. Many women wanted to play
part in the defence of Britain. This force was set up
a wide variety of jobs that had previously been undertaken
men. Thus the men were released for active duty.
for "enemy aircraft approaching".
special type of diode valve that has resonant cavities
The anode. The valve has to operate within a strong magnetic
field. The type invented by Randle and Boot in 1940, paved
way for much more precise centimetric radars to be produced.
They were much more powerful generators of microwaves
anything that had gone before.
first operational defensive radar system in the world.
The chain of stations was constructed between 1937 and
along the east coast of Britain. The radar operated at
wavelength of 12 metres.
development from the 'CH' system that was designed to
low flying aircraft in particular. It worked on 1.5m wavelengths.
A further modification was 'Chain Home, extra low' which
on 10 cms wavelengths.
aerial; usually a folded rod and designed to work at
approximately half the wavelength for the particular frequency
Control Interception' was the term given to the technique
of directing fighter planes from a control centre on the
combination of observation, radar and radio telephones
to direct the pilot to intercept the enemy planes and
in the most
strategically advantageous way.
radio-navigational system that relied upon pulsed
beams being sent to the aeroplane. The system became
operational in March 1942 and the accuracy of bombing
device consisting of 2 pairs of crossed dipoles that can
both the direction and elevation of an incoming radar
two receiver aerials; at a known distance apart. Physically,
Goniometer knob was an integral part of the radar operator's
control panel. A pair of coils (controlled by this knob)
signals from the two aerials in a way that indicates the
of the source.
RAF 'slang' term for the operations control room. Because
control officer could look down on the plotting table;
comparison with a theatre was naturally made.
unit of frequency (1 Hz = 1 cycle / second); named after
Heinricht Hertz in 1888, an early pioneer of electromagnetic
blind bombing system carried entirely in the
aircraft. The system developed from AI but required a
and spiral rotating scanner. The system became fully operational
in January 1943. The phrase 'Home Sweet Home' could have
number of meanings but is generally thought to refer to
aeroplane's ability to 'home in' on its target.
early additional feature to the 'CH' system that allowed
ground controllers to differentiate between 'friendly'
enemy ('foe') aircraft. The friendly aircraft were fitted
with a small
transmitter that sent a coded signal at the same frequency
interrogating radar that, when received, could be incorporated
the cathode ray tube display. Any aircraft not sending
could be assumed as hostile.
techniques that were used to over power, confuse and
distort the radar and radio-location equipment used by
Many ingenious methods were employed an both sides to
special receiver that was installed on German 'U'-boats.
receiver could detect the signals from an ASV equipped
This early warning equipment allowed the surfaced 'U'-boats
escape by crash diving.
|| The specific
component in a radar transmitter circuit that
generates pulsed waves of electromagnetic energy.
was another ingenious bombing guidance system but this
was controlled from the ground. Radio beacons transmitted
'guide-path' signal which the aircraft crew could receive
series of morse codes; dashes if the plane was to the
right of the
exact flight path and dots if they were to the left of
it. If the plane
on the correct target flight path the navigator would
sound like an oboe.
type of transmitter aerial employed for centimetric
radars. A dish-like reflector ensures that the transmitted
leaves the dish as a narrow pencil-like beam.
formalized 'language' used between ground control and
pilot. The terminology evolved using terms that were clearly
during battle and less likely to be mistaken over the
Examples include: "bandits", " 12 o'clock
high" and "tally ho".
The letters of the alphabet were used to identify individual
eg. "T for Tango" or "V for Victor".
This scheme significantly
improved the accuracy of communication between the ground
staff and the pilot.
Position Indicator' was a great advance in the field of
radar display. G.W. Dummer replaced the standard horizontal
'left to right' trace with a rotating radial trace emanating
center of the screen. A pre-requisite for this development
been an effective synchronized rotating aerial. Transparent
could be superimposed on the screen to give a readily
understandable picture of the activity in the sky above.
. A misleading term that really
'Radio Location' and was the general term used to describe
the area of science involved. The Americans coined the
'Radar' and it was rapidly adopted.
|| The Skiatron
was a modification of the PPI display that involved
The back-projection of the image underneath a large ,
glass table. The idea was to improve the visual display
controllers and operators alike could see what was happening.
Light Control. The integrated set of arrangements that
allowed a group of search lights to pick out and hold
that refers to the 'no signal' electron trace seen upon
an oscilloscope screen. The length of the trace can be
and the time taken to make each sweep can be calculated.
from this fundamental parameter that the time for a signal
return (as an echo) can be calculated and then, knowing
speed of the wave, target range can be determined.
. The title given
to the unit set up at Worth Matravers in May 1940. The
was deliberately misleading as the work carried out had
to do with telecommunications. The staff, somewhat
irreverently said later, that it stood for "travels
in reference to their constantly being relocated.
and square-section tubes that were used to take
receiver signals from the aerial to the receiver. The
was far less than using conventional cables. The wave
reflect off the inside of the tube. Internal dimensions
known as 'chaff'. This was a device that was used
as an effective 'jamming' technique. Thin strips of aluminium,
about 21 cms long were dropped from an aeroplane and would
create 'blips' on the enemy radar with the same dimensional
characteristics as a real plane(s). The system was used
effect to mask the true location of the D-day landings;
of directional aerial consisting of a folded half-wave
dipole and up to 20 'director' rods in front and one reflector
rod behind. Still commonly seen today for domestic television