Site Name: RAF Holmpton R7 Mk III ROTOR Radar Bunker
off South Leys Road
Sub Brit site visit: 24th July 2004
[Source:RAF Holmpton Archive & Nick Catford]
Originally all the radars at RAF Holmpton were to be clustered round
the R3 control centre apart from the Type
7 which was remotely sited at South Leys, 2km north west of the
A Type 7 aerial array over an R7 Mk III bunker
The transmitter, receiver and motor for turning the aerial array were
located underground in a bunker designated as an R7 and known as a 'well'.
During the ROTOR period two different types of R7 bunker were utilised.
Where the Type 7 radar was located close to the R3 operations block
it was housed in an R7 Mk II bunker which consisted of a single room.
If the R7 was at a dispersed location a larger R7 Mk III was built which
consisted of three rooms. Because of the distance from the main site,
an R7 Mk III required its own IFF
and an Mk 10 IFF was mounted on a Type 14 plinth, turntable and cabin
this combination was known as a Type 79.. This was located a short distance
to the north of the R7 bunker with a small brick built electricity sub
Plan of an R7 Mk III bunker
The Type 7 was developed in the early years of WW2 as parallel development of the Chain Home Low (CHL) radar by the addition of a height-finding capability and a Plan Position Indicator (PPI) display.
For reception the dipoles in each stack could be combined in four different
ways providing beams at difference angles of elevation for height finding.
Switching between beams was done automatically or on a pulse-to-pulse
basis using a capacity switch in the feeders.
Photo: The extant Type 79 plinth and power house
Photo by Nick Catford
WW2 R7's were known at Mk. I, post war this equipment was upgraded and a small R7 'well' designed for use on the radar site was designated Mk. II and a much larger R7 Mk. III was for remote sites up to 2 km from the main site containing IFF facilities. Both Mks. II and III were later re-engineered to Mks. IV and V standard respectively.
For further information and pictures of the RAF Holmpton
R7 bunker click here
Last updated 19th January 2006
© 2006 Subterranea Britannica