The Racal RA17 C18

The RA17C18 is modified version of the RA17C12, having a delay compensated IF amplifier and an additional IF output. It is a North American version of the RA17, ie., it uses all BNC and SO239 connectors, all fasteners have unified threads, and the harmonic mixer (V4) is a 6AS6. It has no BFO, and the IF bandwidth selector has only four positions: 13KHz, 6.5KHz, 3KHz, and 1.2KHz. The receiver is instead equipped with a DC-coupled 'Video' output, and a front panel 'DC Zero' adjustment which relates to it. The 'Shaper Level' control adjusts a peak-level clipping circuit, which affects both the video and audio outputs.

The photograph below shows the solid-state power supply and the specialised IF amplifier module. The set originally had a permanently attached mains lead and a voltage selector, but these were replaced (by the author, in ca. 1982) with an input receptacle and two switched mains outlets for adapters (the 3-pole Belling-Lee connector used is no longer type-approved in the UK and is scheduled for replacement).

Valve Complement
  Type Function
V1 6AU6A  
V2 6AU6A  
V3 ECC189 Cascode RF amp.
V4 6AS6W Dual control pentode, harmonic mixer.
V5 6AU6WB  
V6 6AU6A  
V7 E180F  
V8 6AU6A  
V9 E180F  
V10 6AU6A  
V13 EK90  
V14 EF93 1st IF
V16 EF93 2nd IF
V17 EF93 IF amp for wide IF output
V18 CV4007 Double diode, AVC.
V19 M8182 2 x Cathode Follower: IF Out Wide, and Video Out.
V20 Not Used HT rectifier, replaced by silicon bridge.
V21 CV4007 Double diode; Detector and Peak Clipper.
V22 EL90 AF Output
V23 ECC81  
V24 Not Used AGC delay, uses 1N916 diode (MR9).
V25 0A2 Voltage stabiliser, for video output HT.

IF Amplifier Circuit Diagram (58K GIF, 1315 x 771 pixels)


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