|
TERM
|
EXPLANATION
|
|
| 'AI'
|
Air
(or airborne) Interception. Special electronic interception
equipment mounted in an aeroplane. Space inside an aeroplane
dictated that much shorter wavelengths than those used
for
ground-based equipment had to be developed. Centimetric
radar
proved to be the defining breakthrough.
|
| 'ASV'
|
Air
to surface vessl radar. This was a system particularly
used for
detecting 'U'-boats. New and novel scanning aerials were
needed.
|
|
| 'ATS'
|
The
Auxiliary Territorial Service. Many women wanted to play
their
part in the defence of Britain. This force was set up
to undertake
a wide variety of jobs that had previously been undertaken
by
men. Thus the men were released for active duty.
|
|
| 'Bandits'
|
RAF slang
for "enemy aircraft approaching". |
|
| Cavity
Magnetron |
A
special type of diode valve that has resonant cavities
built into
The anode. The valve has to operate within a strong magnetic
field. The type invented by Randle and Boot in 1940, paved
the
way for much more precise centimetric radars to be produced.
They were much more powerful generators of microwaves
than
anything that had gone before.
|
|
| 'Chain
Home' |
[CH]: The
first operational defensive radar system in the world.
The chain of stations was constructed between 1937 and
1939
along the east coast of Britain. The radar operated at
a
wavelength of 12 metres.
|
|
| 'Chain
Home, Low' |
A
development from the 'CH' system that was designed to
detect
low flying aircraft in particular. It worked on 1.5m wavelengths.
A further modification was 'Chain Home, extra low' which
worked
on 10 cms wavelengths.
|
|
| Dipole |
A simple
aerial; usually a folded rod and designed to work at
approximately half the wavelength for the particular frequency
being used.
|
|
| G.C.I.
|
'Ground
Control Interception' was the term given to the technique
of directing fighter planes from a control centre on the
ground. A
combination of observation, radar and radio telephones
were used
to direct the pilot to intercept the enemy planes and
in the most
strategically advantageous way.
|
|
| GEE |
A ground-based
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
raids
improved.
|
|
| Goniometer |
A
device consisting of 2 pairs of crossed dipoles that can
interpret
both the direction and elevation of an incoming radar
echoes from
two receiver aerials; at a known distance apart. Physically,
the
Goniometer knob was an integral part of the radar operator's
control panel. A pair of coils (controlled by this knob)
balance the
signals from the two aerials in a way that indicates the
direction
of the source.
|
|
| 'Happidrome'
|
An
RAF 'slang' term for the operations control room. Because
the
control officer could look down on the plotting table;
a
comparison with a theatre was naturally made.
|
|
| Hertz
|
The
unit of frequency (1 Hz = 1 cycle / second); named after
Heinricht Hertz in 1888, an early pioneer of electromagnetic
radiation research.
|
|
| H2S
|
A self-contained
blind bombing system carried entirely in the
aircraft. The system developed from AI but required a
downward
and spiral rotating scanner. The system became fully operational
in January 1943. The phrase 'Home Sweet Home' could have
a
number of meanings but is generally thought to refer to
the
aeroplane's ability to 'home in' on its target.
|
|
| I.F.F.
|
An
early additional feature to the 'CH' system that allowed
the
ground controllers to differentiate between 'friendly'
aircraft and
enemy ('foe') aircraft. The friendly aircraft were fitted
with a small
transmitter that sent a coded signal at the same frequency
as the
interrogating radar that, when received, could be incorporated
in
the cathode ray tube display. Any aircraft not sending
this signal
could be assumed as hostile.
|
|
| 'Jamming'
|
The various
techniques that were used to over power, confuse and
distort the radar and radio-location equipment used by
the enemy.
Many ingenious methods were employed an both sides to
fool the
other.
|
|
| 'METOX'
|
A
special receiver that was installed on German 'U'-boats.
This
receiver could detect the signals from an ASV equipped
aircraft.
This early warning equipment allowed the surfaced 'U'-boats
to
escape by crash diving.
|
|
| Modulator |
The specific
component in a radar transmitter circuit that
generates pulsed waves of electromagnetic energy.
|
|
| OBOE
|
This
was another ingenious bombing guidance system but this
was controlled from the ground. Radio beacons transmitted
a
'guide-path' signal which the aircraft crew could receive
as a
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
hear a
sound like an oboe.
|
|
| Parabolic
array |
An advanced
type of transmitter aerial employed for centimetric
radars. A dish-like reflector ensures that the transmitted
signal
leaves the dish as a narrow pencil-like beam.
|
|
| 'Pipsqueak'
|
The
formalized 'language' used between ground control and
the
pilot. The terminology evolved using terms that were clearly
heard
during battle and less likely to be mistaken over the
radio.
Examples include: "bandits", " 12 o'clock
high" and "tally ho".
The letters of the alphabet were used to identify individual
aircraft
eg. "T for Tango" or "V for Victor".
This scheme significantly
improved the accuracy of communication between the ground
staff and the pilot.
|
|
| P.P.I
|
The 'Plan
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
from the
center of the screen. A pre-requisite for this development
had
been an effective synchronized rotating aerial. Transparent
maps
could be superimposed on the screen to give a readily
understandable picture of the activity in the sky above.
|
|
| 'RDF'
|
Radio
Direction Finding…. A misleading term that really
meant
'Radio Location' and was the general term used to describe
the
the area of science involved. The Americans coined the
term
'Radar' and it was rapidly adopted.
|
|
| Skiatron
|
The Skiatron
was a modification of the PPI display that involved
The back-projection of the image underneath a large ,
circular
glass table. The idea was to improve the visual display
so that
controllers and operators alike could see what was happening.
|
|
| 'SLC'
|
Search
Light Control. The integrated set of arrangements that
allowed a group of search lights to pick out and hold
aircraft
targets.
|
|
| 'timebase'
|
The term
that refers to the 'no signal' electron trace seen upon
an oscilloscope screen. The length of the trace can be
adjusted
and the time taken to make each sweep can be calculated.
It is
from this fundamental parameter that the time for a signal
to
return (as an echo) can be calculated and then, knowing
in the
speed of the wave, target range can be determined.
|
|
| T.R.E.
|
Telecommunications
Research Establishment…. The title given
to the unit set up at Worth Matravers in May 1940. The
name
was deliberately misleading as the work carried out had
nothing
to do with telecommunications. The staff, somewhat
irreverently said later, that it stood for "travels
'round England"
in reference to their constantly being relocated.
|
|
| Waveguides |
Round-section
and square-section tubes that were used to take
receiver signals from the aerial to the receiver. The
signal loss
was far less than using conventional cables. The wave
would
reflect off the inside of the tube. Internal dimensions
were
therefore critical.
|
|
| 'Window'
|
Alternatively
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
to great
effect to mask the true location of the D-day landings;
6th June
1944.
|
|
| 'Yagi'
array |
A type
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
reception.
|
|
