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Technical details

Type 277F was a 10 centimetre surface/low air search set introduced into naval service in 1944. Sometimes it's described as the most successful wartime British naval radar. Using 500 kilowatts of power, its 4.5 degree by 4.5 degree beam could detect a battleship at 23 nm. (1)

Frequency 3000 MHz
Peak Power 500 kW
PRF 500 Hz
Pulse Width 1.9 uS
Rx Noise level -102 dBm
Antenna Gain 31 dB
Beam Width 5
Max Range 160 nm

Main equipment of a 277F radar station(2)

Travelling Wave Tube Amplifier - Marconi type TF 1278/1
L26 unit:
- Upper chassis; Rectifier Unit, Oscillator G50, Display Unit
- Lower chassis; Cathode Follower Unit, Amplifier IF M70
Control unit - AUK & ANU aerials
Discriminator Unit - Iso Echo
Display Unit, HPI design B
Display Unit, 3 range
Display Unit, 4 range
Generator, Strobe design F
Iindicator, Standing wave ratio
Modulator 3BA
Output unit SE2
Oscillator G208
Range Transmission unit 'B'
Receiver P51
Rectifier unit, design 'S'
Stabiliser unit - AUK & ANU aerials
Swept gain unit
Transmitter 9T
Wattmeter G93
Wave Monitor G86
Board Control, 5kW, 500 & 50 Hz
Amplifier, Travelling Wave Tube

Aspirator Assembly, Display Units

Transmitter 9T Pulse Widths - 2 & 0.5uS at 500kW
AUK Antenna 1.35m in diameter The antenna had de-icing heaters running through the rear of the parabolic dish.

P51 (Head Amp) Receiver - Crystal mixer with two VR136 (CV1136) valve forming a 60MHz stagger tuned amplifier with 20db gain and 1MHz bandwidth providing -90dBm sensitivity.
Amplifier IF M70 Five stages of 60MHz IF amplification (1.2 MHz bandwidth) then a single valve detector followed by an output valve operating as a cathode follower delivering the video output. Used six CV1091 and one CV1092.
Iso-echo Discriminator This was the only transistorised part of the radar, being introduced in the 1960's. It used four transistors to provide a schmitt trigger operating on the radar video.

Test Equipment supplied by the Bureau to the Obs/Radio was minimal - typically just an AVO model 40 multimeter.(2) Though by 1968 Cloncury sported the more modern AVO 8!(4)
Stations with Iso-echo fitted were issued with a Marconi TF801A signal generator and later some stations were issued with a BWD type 511 oscilloscope.(2)

The PRF was developed from the 500Hz motor Alternater output

(2) Equipment Establishment Table T46 for Radar type 277F (1974)
(3) BR1280 Servicing Manual for Types 276/277/293 EH61 (1946)
(4) Reg Carter (private communication)