The R-1123/ARC-73 receiver with on top the RF module with mechanical tuning of the RF and variable IF, and the High-, and Low frequency oscillators. On the bottom is the fixed IF and audio module, and either the 28Vdc only or 115V/400 cps power supply.

Top:  Control panel 614U  ( C-4074/ ARC-73)


614U-1     to control  51X-2 + 17L7  from 118...151.95 MHz;

614U-2         same but with gray front

614U-3      to control  51X-2 + 51V-3 (GS)   from 108...135.95 MHz;

614U-4          same but with gray front

614U-5      to control 17L7 + 51X-2 from 116 - 149.95 MHz

614U-6          same, with additional outputs for GlideSlope freq. control

614U-7          same with additional outputs for DME and GS control


614U-1 and –5 have a SCS or DCS/DCD selector. In Dual Channel mode, the transmit frequency is 6MHz higher than the shown Rx frequency.


Left:  Both the receiver and the transmitter have dials to show the frequency.  Shown are those on front of the  receiver, with the twenty crystals of the low frequency oscillator directly behind the dials.  The 22  high frequency oscillator crystals are on the rear end of the receiver.

The transmitter has the 18 high frequency crystals directly behind the dials and the 20 low frequency crystals halfway  the unit.


Updated 21 July 2012

Click to enlarge


The transmitter and receiver are fully independent, each with its own mechanical tuning, crystal oscillators, and power supply. Only the antenna, dual  shock mount and the control panel are shared. With the independent tuning mechanisms, single channel simplex (SCS)

and dual channel simplex or duplex (DCS/DCD) was possible with a suitable control panel.


  The transmitter covers 116-149.95 MHz AM in 50 kHz steps, 680 channels,

                                     ( 118-151.95 MHz for the 17L-7 )

     Outputs:  25 watts RF  into 52 ohms, and 100mw side-tone level into 500 Ohms, 

      Inputs:  Mic impedance 100 Ohms.   ( 30mA  dc bias provided )

      Power requirement is  1A/115V/400Hz  or 28Vdc/ 7A at full Tx power and  90% AM

      plus 1A for transmitter tuning for less than 7 seconds. 


The receiver  covers 108-151.95 MHz in 50 kHz steps, 880 channels.   Sensitivity 3uV 

     Output  100mW (7Vrms) audio into  500 Ohms.

     Power requirements for the receiver DC-only version are 27 VDC @ 1.2A , Tuning adds 1A.    

     The ac version requires 115V @ 0.21A and  27Vdc@0.3A.

     The receiver has 9 tubes and 1 transistor ( in the ac power supply version *)

               *) The DC-only  power supplies add each  4 transistors ( 2 de-spiking, 2 inverter)


The receiver was either combined with the 344B-1 Instrumentation Unit and a horizontal polarized antenna, or with the 17L-7 transmitter and a vertical polarized antenna.   The Instrumentation Unit decodes the VOR and LOC signals, ready for connection to a course indicator.

  614U or  C-4074 Remote tuning control has a frequency selector with mechanical digital frequency  display, on/off switch, squelch and volume control and either a  COM/NAV or SCS/DCS switch. In Dual channel mode, the transmit frequency is 6MHz above the (shown) receive frequency.


Schematic diagrams :

 - ARC73 circuit diagrams

 - Leaflet 17L-7A

 - Control  614U –1 or -2

     , or this one as pdf

ARC-73 VHF transceiver

VHF Aircraft radio set made by Collins Radio Co., with separate transmitter and receiver


ARC-73     Collins

 R-1123A   (51X2B)   receiver,        108-151.95 MHz in 50 kHz steps, 880 channels

  T-879      (17L-7A)   transmitter,   116-149.95 MHz in 50 kHz steps, 700 channels

 C-4074        (614U)   remote tuning control

 MT-2699  ( 390E-2)   Dual Shockmount

The  original Collins designation is generally used, even in military aircraft.





FM Communication






FM Comm panels


VHF Communication


  TR 1985


UHF Communication








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  USB control


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