Chain Home radar installations were normally composed of two sites.
One compound contained the transmitter towers with associated structures, and a second compound, normally within a few hundred metres distance, contained the receiver masts and receiver equipment block where the operators (principally WAAF, Women's Auxiliary Air Force) worked.
The CH system was, by modern terminology, a "bistatic radar", although modern examples normally have their transmitters and receivers far more widely separated.

The transmitter antenna consisted of four steel towers 360 feet (110 m) tall, set out in a line about 180 feet (55 m) apart.
Three large platforms were stationed on the tower, at 50, 200 and 350 feet off the ground.
A 600 ohm transmission cable was suspended from the top platform to the ground on either side of the platform (only on the inside of the end towers).
Between these vertical feed cables were the antennas proper, eight half-wave dipoles strung between the vertical cables and spaced ½ of a wavelength apart.
They were fed from alternating sides so the entire array of cables was in-phase, given their ½ wavelength spacing.
Located behind each dipole was a passive reflector wire, spaced 0.18 wavelength back.

The resulting curtain array antenna produced a horizontally polarised signal that was directed strongly forward along the perpendicular to the line of the towers.
This direction was known as the line of shoot, and was generally aimed out over the water.
The broadcast pattern covered an area of about 100 degrees in a roughly fan-shaped area, with a smaller side lobe to the rear, courtesy of the reflectors, and much smaller ones to the sides.
When the signal reflected off the ground it underwent a ½ wavelength phase-change, which caused it to interfere with the direct signal.
The result was a series of vertically-stacked lobes about 5 degrees wide from 1 degree off the ground to the vertical.
The system was later expanded by adding another set of four additional antennas closer to the ground, wired in a similar fashion.

The receiver consisted of an Adcock array consisting of four 240 foot (73 m) tall wooden towers arranged at the corners of a square.
Each tower had three sets (originally two) of receiver antennas, one at 45, 95 and 215 feet off the ground.
The mean height of the transmitter stack was 215 feet, which is why the topmost antenna was positioned at the same altitude in order to produce a reception pattern that was identical to the transmission.
A set of motor-driven mechanical switches allowed the operator to select which antenna was active.
The output of the selected antenna on all four towers was sent to a single radiogoniometer system (not Watt's own huff-duff solution).
By connecting the antennas together in X-Y pairs the horizontal bearing could be measured, while connecting together the upper and lower antennas allowed the same goniometer to be used to measure the vertical angle.

Two physical layout plans were used, either 'East Coast' or 'West Coast'.
West Coast sites replaced the steel lattice towers with simpler guy-stayed masts, although they retained the same wooden towers for reception.
East Coast sites had transmitter and receiver blocks protected with earth mounds and blast walls, along with separate reserve transmitter and receivers in small bunkers with attached 120 ft aerial masts.
These reserves were in close proximity to the respective transmitter/receiver sites, often in a neighbouring field.
West Coast sites relied on site dispersal for protection, duplicating the entire transmitter and receiver buildings.
Chain Home radar installations were normally composed of two sites. One compound contained the transmitter towers with associated structures, and a second compound, normally within a few hundred metres distance, contained the receiver masts and receiver equipment block where the operators (principally WAAF, Women's Auxiliary Air Force) worked. The CH system was, by modern terminology, a "bistatic radar", although modern examples normally have their transmitters and receivers far more widely separated.
The transmitter antenna consisted of four steel towers 360 feet (110 m) tall, set out in a line about 180 feet (55 m) apart. Three large platforms were stationed on the tower, at 50, 200 and 350 feet off the ground. A 600 ohm transmission cable was suspended from the top platform to the ground on either side of the platform (only on the inside of the end towers). Between these vertical feed cables were the antennas proper, eight half-wave dipoles strung between the vertical cables and spaced ½ of a wavelength apart. They were fed from alternating sides so the entire array of cables was in-phase, given their ½ wavelength spacing. Located behind each dipole was a passive reflector wire, spaced 0.18 wavelength back.
The resulting curtain array antenna produced a horizontally polarised signal that was directed strongly forward along the perpendicular to the line of the towers. This direction was known as the line of shoot, and was generally aimed out over the water. The broadcast pattern covered an area of about 100 degrees in a roughly fan-shaped area, with a smaller side lobe to the rear, courtesy of the reflectors, and much smaller ones to the sides. When the signal reflected off the ground it underwent a ½ wavelength phase-change, which caused it to interfere with the direct signal. The result was a series of vertically-stacked lobes about 5 degrees wide from 1 degree off the ground to the vertical. The system was later expanded by adding another set of four additional antennas closer to the ground, wired in a similar fashion.
The receiver consisted of an Adcock array consisting of four 240 foot (73 m) tall wooden towers arranged at the corners of a square. Each tower had three sets (originally two) of receiver antennas, one at 45, 95 and 215 feet off the ground. The mean height of the transmitter stack was 215 feet, which is why the topmost antenna was positioned at the same altitude in order to produce a reception pattern that was identical to the transmission. A set of motor-driven mechanical switches allowed the operator to select which antenna was active. The output of the selected antenna on all four towers was sent to a single radiogoniometer system (not Watt's own huff-duff solution). By connecting the antennas together in X-Y pairs the horizontal bearing could be measured, while connecting together the upper and lower antennas allowed the same goniometer to be used to measure the vertical angle.
Two physical layout plans were used, either 'East Coast' or 'West Coast'. West Coast sites replaced the steel lattice towers with simpler guy-stayed masts, although they retained the same wooden towers for reception. East Coast sites had transmitter and receiver blocks protected with earth mounds and blast walls, along with separate reserve transmitter and receivers in small bunkers with attached 120 ft aerial masts. These reserves were in close proximity to the respective transmitter/receiver sites, often in a neighbouring field. West Coast sites relied on site dispersal for protection, duplicating the entire transmitter and receiver buildings.
Chain Home